Canadian Journal of Fisheries and Aquatic Sciences, Nov 1, 1991
Responses of stream periphytic algae and benthic insects to increases in dissolved inorganic phos... more Responses of stream periphytic algae and benthic insects to increases in dissolved inorganic phosphorus (P) were assessed in a streamside mesocosm. Controls and treatments were colonized continuously in summer by biota from the stream. P was maintained in the treatments at 10 μg∙L−1, [Formula: see text] times the concentration in the controls. In the treatments the biomass of chlorophyll a reached 3.5 times that of the controls, accompanied by an increase in Cyanophyta relative to diatoms. No difference was detectable in the numbers of insects drifting from controls and treatments. Numbers of individuals emerging (> 40 species) from the treatments over 7 wk were 2.2 times those from the controls. In both controls and treatments, 77% or more of emerging insects were Chironomidae. After week 7 the density of benthic insects in the treatments, determined without size selection, was 1.75 times that of the controls; size distributions in treatments and controls were similar. Addition of P, therefore, increased the food of insects and resulted in a doubling of their survival to emergence.
Canadian Journal of Fisheries and Aquatic Sciences, Nov 1, 1997
Additions of inorganic N and P to replicated stream mesocosms were used to test the hypothesis th... more Additions of inorganic N and P to replicated stream mesocosms were used to test the hypothesis that production of the benthic food web in the flow-controlled Nechako River, B.C., was N and P limited. N, P, and N + P additions were contrasted with controls to determine the responses of periphyton and macroinvertebrates over a 33-day period in late spring. Periphyton accrual under N + P addition was greater than two times that of the controls, and N alone produced a moderate increase. Periphyton showed relatively little response to P addition compared with controls. Macroinvertebrates, especially orthocladiine midges and mayflies, increased in density under N or N + P additions, in contrast with P additions and controls. Increased emergence rates of adult aquatic insects from the mesocosms were consistent with increases observed in benthic invertebrates. The results showed nutrient limitation of benthic productivity and that algal and benthic invertebrate responses were closely coupled. N was most limiting, but with additions of inorganic N as low as 10 µg⋅L-1 , P became limiting. The benthic invertebrates that increased most in abundance corresponded to the predominant prey in chinook salmon (Oncorhynchus tshawytscha) fry diets at the time of the experiment. Résumé : Nous avons ajouté du N et du P inorganiques dans une série de mésocosmes lotiques pour valider l'hypothèse selon laquelle la production de la chaîne alimentaire benthique dans la rivière Nechako, un cours d'eau de Colombie-Britannique à débit contrôlé, était limitée en N et en P. Les effets des ajouts de N, de P et de N + P ont été comparés à des valeurs témoins afin de déterminer les réponses du périphyton et des macroinvertébrés sur une période de 33 jours de la fin du printemps. L'accroissement du périphyton pour un ajout de N + P était plus du double que pour les témoins, et l'ajout de N seul a entraîné une augmentation modérée. Par contre, l'effet d'un ajout de P a eu relativement peu d'effet sur le périphyton. La densité des macroinvertébrés, particulièrement les chironomidés orthocladiinés et les éphéméroptères, a augmenté en cas d'ajout de N ou de N + P, mais pas en cas d'ajout de P ni dans les milieux témoins. Les taux accrus d'émergence observés chez les insectes aquatiques adultes des mésocosmes étaient conformes aux augmentations observées chez les invertébrés benthiques. Les résultats ont montré que la production benthique était limitée par les éléments nutritifs et que les réactions des algues et des invertébrés benthiques étaient étroitement liées. C'est l'azote qui était l'élément le plus limitant; pour des ajouts de N inorganique de seulement 10 µg⋅L-1 , P est devenu limitant. Les invertébrés benthiques dont l'abondance a le plus augmenté correspondaient aux principales proies des alevins du saumon quinnat (Oncorhynchus tshawytscha) au moment de l'expérience. [Traduit par la Rédaction]
Canadian Journal of Fisheries and Aquatic Sciences, Jun 1, 1987
Periphyton accumulation rates and alkaline phosphatase activity were examined in reaches of the K... more Periphyton accumulation rates and alkaline phosphatase activity were examined in reaches of the Keogh River, British Columbia, fsllowing additions of grain and inorganic fertilizer as separate treatments during spring-summer 1981. Two different levels of N and P addition were used: one to attain ambient N and P concentrations of 280 and 1 5 pg-L-I, respectively, and the other to attain 400 and 20 pg-L-', respectively. Grain (rolled barley) was added monthly at 280 gmrn-2. N and P additions increased chlorophyll a accrual rates by more than an order of magnitude. Diatoms dominated the periphyton community until midsummer. In july and most of August, the relative importance of chlorophytes increased and biomass levels declined markedly in spite of continued nutrient additions. Grain additions resulted in no detectable change in periphyton accrual, but alkaline pkosphatase activity increased by 35% over control levels. These results suggest that additions of labile organic matter to nutrient-deficient coastal streams can increase autotrophic P deficiency. Based on responses of juvenile salmonids, additions of inorganic nutrients to increase autotrophic production can maximize tropkic enhancement in nutrient-deficient streams. Les auteurs ont 6tudie les taux d'accumulation et I'activit6 de la phospkatase alcaline chem le periphyton puplant des sections de la riviere Keogh (Colombie-Britannique) apr6s leapport separe de fertilisants organiques et inorganiques au printemps et 2 l'$t6 de 1981. Deux teneurs diffkrentes en RI et P ont ete uti%isees : la premiere visait une concentration ambiante respective de IV et de P de 200 et de 15 pg.L-' et la seconde, de 400 et de 26 pg*L-' respectivement. L'apprt mensuel de ckreales (flocons d'orge) s'est effectue un taux de 280 g-m-2. L'apport de N et de P a entraine une augmentation des taux d'accurnulatisn de chlorophylle a de plus d'un srdre de grandeur. Les diatom& dominaient la communaute Mriphytonique jusqu'a la mi-et6. En juillet et pendant la plus grande partie dlaoOt, l'importance relative des chlorophycopkytes a augment6 tandis que les niveaux de la biomasse ont folfernent baisd malgre l'appolf continu de bio68&nents. L'addition de cer6ales n'a pas entrain6 de variation discernable du taux d'accumulatisn du periphyton, mais I'activite de la phosphatase alcaline a augment6 de 35 % par rapport au niveau t6moin. Les rksultats portent A croire que I'apport de rnatieres organiques labiles dans des cours d'eau cbtiers pauvres en bio6l6ments p u t accroitre le deficit en P autotrophe. Dfapr&s les reactions des salmsnid6s juveniles I'apport de bio6Iements inorganiques en vue d'accrsftre la production autotrophe peut maximiser la stimulation des niveaux trophiques dans les cours d'eau pauvres en bioel6ments.
The Coho Salmon, Oncorhynchus kisutch, is one of seven species of Pacific salmon and trout native... more The Coho Salmon, Oncorhynchus kisutch, is one of seven species of Pacific salmon and trout native to northeastern Pacific Ocean watersheds. The species is typically anadromous; adults reproduce in fresh water where juveniles reside for 1-2 years before seaward migration after which the majority of growth occurs in the ocean before maturation at 2-4 years old when adults return to fresh water to spawn. Here, we report maturation of Coho Salmon in two freshwater lakes on the north coast of British Columbia apparently without their being to sea. A total of 15 mature fish (11 males and four females) were collected in two lakes across two years. The mature fish were all at least 29 cm in total length and ranged in age from three to five years old. The occurrence of Coho Salmon that have matured in fresh water without first going to sea is exceedingly rare in their natural range, especially for females. Such mature Coho Salmon may represent residual and distinct breeding populations from those in adjacent streams. Alternatively, they may result from the ephemeral restriction in the opportunity to migrate seaward owing to low water levels in the spring when Coho Salmon typically migrate to sea after 1-2 years in fresh water. Regardless of their origin, the ability to mature in fresh water without seaward migration may represent important adaptive life history plasticity in response to variable environments.
Canadian Journal of Fisheries and Aquatic Sciences, May 1, 1994
Commercial formulations of the insecticidal bacterium Bacillus thuringieresis var. kurstaki (Btk)... more Commercial formulations of the insecticidal bacterium Bacillus thuringieresis var. kurstaki (Btk) are frequently sprayed over bodies of water. The hypothesis that Btk poses a threat to stream communities was tested using streamside, flow-through mesocosms which received water and invertebrate colonists from a secondorder stream in southwestern British Columbia; low (58 BIU/ha) and high (25800 BIU/ha) treatment levels were contrasted with controls. There were no significant differences in the density or composition of benthos sampled 7 d after Btk application. The densities were highest in the high-dose mesocosms. There were no significant differences in emergence rate of adults due to treatment. During the 2.5-$8 treatment, there were marginally elevated drift rates of the mayfly Baetis when exposed to the solution, but these differences were negated during the remainder of the 24-h period. Leaf packs lose significantly more mass in controls than in high-dose mesocosrns, but there were no significant differences in the numbers of macroinvertebrates on those leaf packs. There was no evidence that addition of Btk to stream mesocosms created adverse effects for this benthic community, even at >1 08 times expected exposure rates. II arrive souvent que les formulations commerciales de la bacterie insecticide BacilBus thuringr'erpsis var. kurstaki (Btk) sont appliqukes sur des plans d'eau. Nous avons test6 I'hypothese que ie Btk constituait une menace pour [es communautes lotiques en I'essayant sur des m6socosrnes install& au bord de l'eau et aliment& en continu avec de I'eau et des organismes colonisateurs invert6br6s qui provenaient d'un cours d'eau de second ordre du sud-ouest de la Colombie-Britannique; on a compare des cas temoins a des cas A faible dose de traitement (50 BUl/haj et a forte dose de traitement (25 000 BUl/ha). BI n'y a pas eu de diff6rence significative de densit6 ou de composition du benthos echantiilonn6 sept jours apr&s B'application du Btk. Les densit6s les plus 6lev6es ont kt6 observ6es dans les m6socosmes soumis 21 un traitement 21 forte dose. Quant h I'emergence des aduites, i l n'y a pas eu de diff6rence significative attribuable au traitement. Durane les 2'5 h de traitement, il y a eu un taux ieg&rernent sup6rieur de derive des 6ph6m&res Baetis expos6es A la solution, mais ces diffkrences n'ont pas 6t6 observ6es durant la suite des 24 h. Les lots de feuilles preleves dans les stations-t6moins ont perdu beaucoup plus de biomasse que ceux des m6socosrnes exposes 2 de fortes doses de Btk; cependant, il n'y a pas eu de difference significative dans B e nombre de macro-invertebrbs observes sur ces lots. Wien n'indique que B'application de Btk h des m6socosmes lotiques a ehi des effets nuisibles sur cette communaute benthique, mGme h des concentrations > 100 fois le taux d'exposition attendu.
Part way through a year-long water quality field survey, the Capilano Reservoir, located in the G... more Part way through a year-long water quality field survey, the Capilano Reservoir, located in the Greater Vancouver Water District, was drawn down to accommodate earthquake reinforcement work on the Cleveland Dam. This paper reports observations of the effect of drawdown on water quality in the reservoir, in the context of the original study. The drawdown exposed a large zone of deltaic material through which the Capilano River eroded a path up to 2.5 m deep. The deltaic material contained substantial amounts of nitrogen and iron (TKN, 4,470 mg kg-1; total iron, 21,800 mg kg-1). During drawdown, turbidity in the reservoir increased up to 25 times as compared to prior conditions. Ammonium (NH4+-N) and dissolved and particulate iron concentrations in the drawdown zone were up to two orders of magnitude higher than concentrations upstream. Both NH4+-N and dissolved iron were observed to travel the length of the reservoir. Persistence of NH4+-N in the highly oxygenated conditions may be e...
To avoid the formation of organochlorine compounds in pulp products and effluents discharged into... more To avoid the formation of organochlorine compounds in pulp products and effluents discharged into the environment, there is a trend in the North American pulping industry to change from molecular chlorine to chlorine dioxide bleaching. However, chlorate (ClO3−) formed during chlorine dioxide bleaching is known to have toxic effects in some marine algae and has been implicated in environmental problems in the Baltic Sea. This study examined the potential effects of chlorate on natural freshwater, riverine diatom communities characteristic of many rivers in western Canada. Under low ambient river nitrate concentrations (ca. 10 µg•L−1 NO3−N), chlorate additions of up to 500 µg•L1 ClO3 did not reduce the specific growth rates (µ) or change the taxonomic composition of the attached riverine diatom community. The lack of chlorate toxicity to freshwater diatoms suggests that the nitrate uptake and/or reduction mechanism(s) of freshwater diatoms have much higher affinities for NO3 than ClO3...
Canadian Journal of Fisheries and Aquatic Sciences, 2019
The increasing rate of glacier retreat and turbid glacial runoff can have a strong influence on f... more The increasing rate of glacier retreat and turbid glacial runoff can have a strong influence on freshwater ecosystems. Seton and Anderson lakes (British Columbia, Canada) are sockeye salmon (Oncorhynchus nerka) nursery systems. Since the 1940s, the Bridge River Diversion (BRD) introduced glacially turbid water into Seton Lake. To assess the impact of the BRD on the production of Seton Lake, we combined data from limnological surveys with the analysis of subfossil cladocerans and diatoms from sediment cores, using Anderson Lake as a reference. The modern data indicate that the euphotic zone is 14 m shallower and the cladoceran density and biomass are significantly lower in Seton Lake in comparison with Anderson Lake. The paleo-data indicate that following the BRD, the sedimentary fluxes of cladoceran and diatom declined 2- to 10-fold in Seton Lake and remained low thereafter. Together, our data support declines in primary and secondary producers following the BRD, likely due to chang...
The Coho Salmon, Oncorhynchus kisutch, is one of seven species of Pacific salmon and trout native... more The Coho Salmon, Oncorhynchus kisutch, is one of seven species of Pacific salmon and trout native to northeastern Pacific Ocean watersheds. The species is typically anadromous; adults reproduce in fresh water where juveniles reside for 1–2 years before seaward migration after which the majority of growth occurs in the ocean before maturation at 2–4 years old when adults return to fresh water to spawn. Here, we report maturation of Coho Salmon in two freshwater lakes on the north coast of British Columbia apparently without their being to sea. A total of 15 mature fish (11 males and four females) were collected in two lakes across two years. The mature fish were all at least 29 cm in total length and ranged in age from three to five years old. The occurrence of Coho Salmon that have matured in fresh water without first going to sea is exceedingly rare in their natural range, especially for females. Such mature Coho Salmon may represent residual and distinct breeding populations from ...
North American Journal of Fisheries Management, 2006
An innovative coupling of nutrient addition and biomanipulation strategies was applied to Wahleac... more An innovative coupling of nutrient addition and biomanipulation strategies was applied to Wahleach Reservoir in southwestern British Columbia to successfully restore fish populations. Kokanee Oncorhynchus nerka were historically abundant in the reservoir, but the population collapsed over 2 decades. This decline in kokanee abundance and a concurrent decline in the catch rates of rainbow trout Oncorhynchus mykiss coincided with the occurrence of trophic depression in the aging reservoir. It also coincided with the onset of food competition with threespine sticklebacks Gasterosteus aculeatus that were illegally introduced in the 1970s. In 1995 through 2000, the reservoir was fertilized with liquid fertilizer with compositions of 10–34–0 and 28–0−0 at an annual P load of up to 225 mg/m2 of lake water (late May through September) at a molar N:P ratio of 25 in 1995, declining to 13 in 2000. Up to 50,000 age‐0 kokanee (up to 4.5 g) and approximately 20,000 triploid cutthroat trout O. clar...
North American Journal of Fisheries Management, 2005
Coordinated acoustic and trawl surveys were performed to locate aggregations of adult eulachon Th... more Coordinated acoustic and trawl surveys were performed to locate aggregations of adult eulachon Thaleichthys pacificus in the lower Fraser River, British Columbia, during spring 2001 and 2002. Aggregations were encountered in one portion of the study area in both years. They contained mature, spawning, and spent eulachon of both sexes, of which over 80% were spent males. These groups were 880–2,000 m long and averaged 117–140 m wide. Within them, mean fish density was 0.27–0.29 fish/m3 and species composition was 87–99% eulachon. They occurred in 6–8.5 m of water over substrate that was mainly sand with a small fraction of pea gravel. We did not determine whether these eulachon spawned in that area or had congregated there for another purpose, such as holding or migration. Other species occasionally encountered in appreciable numbers were juvenile pink salmon Oncorhynchus gorbuscha and chum salmon O. keta. Mean in situ target strengths of eulachon were −53.3 dB at 123 kHz and −50.3 d...
An on-site continuous-flow trough mesocosm was used to examine changes in the composition and abu... more An on-site continuous-flow trough mesocosm was used to examine changes in the composition and abundance of periphytic algae and benthic invertebrates from additions of a solution of treated acid mine drainage (AMD). Five control and five treatment troughs supported an assemblage of periphyton and invertebrates that colonized from water withdrawn from Foxy Creek, a stream that receives limed AMD from the Equity Silver Mine, central British Columbia, Canada. A water intake for the mesocosm was located upstream of the AMD discharge. The treated AMD was delivered to the apparatus through a pipeline laid in a canal that carried the AMD to Foxy Creek. After three weeks of colonization in the troughs, additions of one part AMD to 10 parts Foxy Creek water was delivered to the treatment troughs and continued for three weeks. Analyses of variance of measurements of abundance and biomass indexes contained high power values and indicated that the AMD addition did not significantly change the algal and insect composition and abundance. Advantages and disadvantages of the mesocosm with regard to the relative sensitivity of the measured parameters for use in examining effects of the AMD additions are discussed. The conclusion was that quantitative on-site experimentation using the mesocosm apparatus is a powerful approach in setting guidelines for AMD discharge mainly due to its capability of integrating ecosystem processes in experiments where hypothesis testing is possible.
Canadian Journal of Fisheries and Aquatic Sciences, 1984
Forest fertilization (435 kg urea∙ha−1) on the Mohun drainage, northern Vancouver Island, during ... more Forest fertilization (435 kg urea∙ha−1) on the Mohun drainage, northern Vancouver Island, during late fall 1979 resulted in a combined increase in urea, ammonia, and nitrate concentrations to 8000 μg N∙L−1 above control levels in streams not protected with 50-m-wide leave (i.e. unfertilized) strips and 350 μg N∙L−1 in those having leave strips. By spring 1980, dissolved nitrogen loads to Mohun Lake increased by a minimum of 55% in the largest basin and 1924% in the smallest basin. This corresponded to fertilizer losses of 2.1% of the total applied from drainages that had leave strips and up to 5.2% from those where the treatment included direct application to stream channels. Nitrogen transport was dominated by reduced nitrogen species and lasted up to 144 d. Relatively small changes in nitrate transport were attributed to low temperatures, which reduced rates of nitrification. Duringthe3-yr prior to forest fertilization, nitrogen and phosphorus were added to the lake at an N:P rati...
Canadian Journal of Fisheries and Aquatic Sciences, 1997
Additions of inorganic N and P to replicated stream mesocosms were used to test the hypothesis th... more Additions of inorganic N and P to replicated stream mesocosms were used to test the hypothesis that production of the benthic food web in the flow-controlled Nechako River, B.C., was N and P limited. N, P, and N + P additions were contrasted with controls to determine the responses of periphyton and macroinvertebrates over a 33-day period in late spring. Periphyton accrual under N + P addition was greater than two times that of the controls, and N alone produced a moderate increase. Periphyton showed relatively little response to P addition compared with controls. Macroinvertebrates, especially orthocladiine midges and mayflies, increased in density under N or N + P additions, in contrast with P additions and controls. Increased emergence rates of adult aquatic insects from the mesocosms were consistent with increases observed in benthic invertebrates. The results showed nutrient limitation of benthic productivity and that algal and benthic invertebrate responses were closely coupled. N was most limiting, but with additions of inorganic N as low as 10 µg⋅L -1 , P became limiting. The benthic invertebrates that increased most in abundance corresponded to the predominant prey in chinook salmon (Oncorhynchus tshawytscha) fry diets at the time of the experiment. Résumé : Nous avons ajouté du N et du P inorganiques dans une série de mésocosmes lotiques pour valider l'hypothèse selon laquelle la production de la chaîne alimentaire benthique dans la rivière Nechako, un cours d'eau de Colombie-Britannique à débit contrôlé, était limitée en N et en P. Les effets des ajouts de N, de P et de N + P ont été comparés à des valeurs témoins afin de déterminer les réponses du périphyton et des macroinvertébrés sur une période de 33 jours de la fin du printemps. L'accroissement du périphyton pour un ajout de N + P était plus du double que pour les témoins, et l'ajout de N seul a entraîné une augmentation modérée. Par contre, l'effet d'un ajout de P a eu relativement peu d'effet sur le périphyton. La densité des macroinvertébrés, particulièrement les chironomidés orthocladiinés et les éphéméroptères, a augmenté en cas d'ajout de N ou de N + P, mais pas en cas d'ajout de P ni dans les milieux témoins. Les taux accrus d'émergence observés chez les insectes aquatiques adultes des mésocosmes étaient conformes aux augmentations observées chez les invertébrés benthiques. Les résultats ont montré que la production benthique était limitée par les éléments nutritifs et que les réactions des algues et des invertébrés benthiques étaient étroitement liées. C'est l'azote qui était l'élément le plus limitant; pour des ajouts de N inorganique de seulement 10 µg⋅L -1 , P est devenu limitant. Les invertébrés benthiques dont l'abondance a le plus augmenté correspondaient aux principales proies des alevins du saumon quinnat (Oncorhynchus tshawytscha) au moment de l'expérience. [Traduit par la Rédaction]
Canadian Journal of Fisheries and Aquatic Sciences, 1990
Nutrient concentrations, periphyton standing crop and size of steelhead trout (Oncorhynchus mykis... more Nutrient concentrations, periphyton standing crop and size of steelhead trout (Oncorhynchus mykiss) and coho salmon (O, kisutch) fry increased after the fertilization of a nutrient-deficient stream with inorganic phosphorus (P) and nitrogen (N). Whole-river fertilization of the Keogh River, British Columbia, during 1983–86 to increase summer average nutrient concentrations from < 1 μg P∙L−1 and 25 μg N∙L−1 to 10–15 μg P∙L−1 and 30–100 μg N∙L−1 resulted in five- to 10-fold increases in periphyton standing crops on artificial substrata and 1.4- to 2.0-fold increases in late-September salmonid fry weights. Diatoms and chlorophytes dominated the algal periphyton on artificial substrata at fertilized sites. Cyanophytes were unimportant despite low N:P ratios in some cases. Juvenile salmonids fed primarily on benthic insects. These results suggest that autochthonous primary production can be an important energy source in forested, middle-order streams, and indicate that the manipulatio...
Canadian Journal of Fisheries and Aquatic Sciences, 1987
Periphyton accumulation rates and alkaline phosphatase activity were examined in reaches of the K... more Periphyton accumulation rates and alkaline phosphatase activity were examined in reaches of the Keogh River, British Columbia, following additions of grain and inorganic fertilizer as separate treatments during spring–summer 1981. Two different levels of N and P addition were used: one to attain ambient N and P concentrations of 200 and 15 μg∙L−1, respectively, and the other to attain 400 and 20 μg∙L−1, respectively. Grain (rolled barley) was added monthly at 280 g∙m−2. N and P additions increased chlorophyll a accrual rates by more than an order of magnitude. Diatoms dominated the periphyton community until midsummer. In July and most of August, the relative importance of chlorophytes increased and biomass levels declined markedly in spite of continued nutrient additions. Grain additions resulted in no detectable change in periphyton accrual, but alkaline phosphatase activity increased by 35% over control levels. These results suggest that additions of labile organic matter to nutr...
Canadian Journal of Fisheries and Aquatic Sciences, 1994
Commercial formulations of the insecticidal bacterium Bacillus thuringiensis var. kurstaki (Btk) ... more Commercial formulations of the insecticidal bacterium Bacillus thuringiensis var. kurstaki (Btk) are frequently sprayed over bodies of water. The hypothesis that Btk poses a threat to stream communities was tested using streamside, flow-through mesocosms which received water and invertebrate colonists from a second-order stream in southwestern British Columbia; low (50 BIU/ha) and high (≥ 5000 BIU/ha) treatment levels were contrasted with controls. There were no significant differences in the density or composition of benthos sampled 7 d after Btk application. The densities were highest in the high-dose mesocosms. There were no significant differences in emergence rate of adults due to treatment. During the 2.5-h treatment, there were marginally elevated drift rates of the mayfly Baetis when exposed to the solution, but these differences were negated during the remainder of the 24-h period. Leaf packs lost significantly more mass in controls than in high-dose mesocosms, but there we...
Page 1. BULLETIN OF MARINE SCIENCE. 55(2-3): 1160-1180. 1994 DEBRIS STRUCTURE PLACEMENTS AND WHOL... more Page 1. BULLETIN OF MARINE SCIENCE. 55(2-3): 1160-1180. 1994 DEBRIS STRUCTURE PLACEMENTS AND WHOLE-RIVER FERTILIZATION FOR SALMONIDS IN A LARGE REGULATED STREAM IN BRITISH COLUMBIA ...
Transactions of the American Fisheries Society, 2003
... Transactions of the American Fisheries Society , 124: 857872. [Taylor &amp;amp; Francis ... more ... Transactions of the American Fisheries Society , 124: 857872. [Taylor &amp;amp; Francis Online], [Web of Science ®], [CSA] View all references). ... View all references; Desloges and Church 198910. Desloges, JR and Church, M. 1989. ...
Canadian Journal of Fisheries and Aquatic Sciences, Nov 1, 1991
Responses of stream periphytic algae and benthic insects to increases in dissolved inorganic phos... more Responses of stream periphytic algae and benthic insects to increases in dissolved inorganic phosphorus (P) were assessed in a streamside mesocosm. Controls and treatments were colonized continuously in summer by biota from the stream. P was maintained in the treatments at 10 μg∙L−1, [Formula: see text] times the concentration in the controls. In the treatments the biomass of chlorophyll a reached 3.5 times that of the controls, accompanied by an increase in Cyanophyta relative to diatoms. No difference was detectable in the numbers of insects drifting from controls and treatments. Numbers of individuals emerging (&gt; 40 species) from the treatments over 7 wk were 2.2 times those from the controls. In both controls and treatments, 77% or more of emerging insects were Chironomidae. After week 7 the density of benthic insects in the treatments, determined without size selection, was 1.75 times that of the controls; size distributions in treatments and controls were similar. Addition of P, therefore, increased the food of insects and resulted in a doubling of their survival to emergence.
Canadian Journal of Fisheries and Aquatic Sciences, Nov 1, 1997
Additions of inorganic N and P to replicated stream mesocosms were used to test the hypothesis th... more Additions of inorganic N and P to replicated stream mesocosms were used to test the hypothesis that production of the benthic food web in the flow-controlled Nechako River, B.C., was N and P limited. N, P, and N + P additions were contrasted with controls to determine the responses of periphyton and macroinvertebrates over a 33-day period in late spring. Periphyton accrual under N + P addition was greater than two times that of the controls, and N alone produced a moderate increase. Periphyton showed relatively little response to P addition compared with controls. Macroinvertebrates, especially orthocladiine midges and mayflies, increased in density under N or N + P additions, in contrast with P additions and controls. Increased emergence rates of adult aquatic insects from the mesocosms were consistent with increases observed in benthic invertebrates. The results showed nutrient limitation of benthic productivity and that algal and benthic invertebrate responses were closely coupled. N was most limiting, but with additions of inorganic N as low as 10 µg⋅L-1 , P became limiting. The benthic invertebrates that increased most in abundance corresponded to the predominant prey in chinook salmon (Oncorhynchus tshawytscha) fry diets at the time of the experiment. Résumé : Nous avons ajouté du N et du P inorganiques dans une série de mésocosmes lotiques pour valider l'hypothèse selon laquelle la production de la chaîne alimentaire benthique dans la rivière Nechako, un cours d'eau de Colombie-Britannique à débit contrôlé, était limitée en N et en P. Les effets des ajouts de N, de P et de N + P ont été comparés à des valeurs témoins afin de déterminer les réponses du périphyton et des macroinvertébrés sur une période de 33 jours de la fin du printemps. L'accroissement du périphyton pour un ajout de N + P était plus du double que pour les témoins, et l'ajout de N seul a entraîné une augmentation modérée. Par contre, l'effet d'un ajout de P a eu relativement peu d'effet sur le périphyton. La densité des macroinvertébrés, particulièrement les chironomidés orthocladiinés et les éphéméroptères, a augmenté en cas d'ajout de N ou de N + P, mais pas en cas d'ajout de P ni dans les milieux témoins. Les taux accrus d'émergence observés chez les insectes aquatiques adultes des mésocosmes étaient conformes aux augmentations observées chez les invertébrés benthiques. Les résultats ont montré que la production benthique était limitée par les éléments nutritifs et que les réactions des algues et des invertébrés benthiques étaient étroitement liées. C'est l'azote qui était l'élément le plus limitant; pour des ajouts de N inorganique de seulement 10 µg⋅L-1 , P est devenu limitant. Les invertébrés benthiques dont l'abondance a le plus augmenté correspondaient aux principales proies des alevins du saumon quinnat (Oncorhynchus tshawytscha) au moment de l'expérience. [Traduit par la Rédaction]
Canadian Journal of Fisheries and Aquatic Sciences, Jun 1, 1987
Periphyton accumulation rates and alkaline phosphatase activity were examined in reaches of the K... more Periphyton accumulation rates and alkaline phosphatase activity were examined in reaches of the Keogh River, British Columbia, fsllowing additions of grain and inorganic fertilizer as separate treatments during spring-summer 1981. Two different levels of N and P addition were used: one to attain ambient N and P concentrations of 280 and 1 5 pg-L-I, respectively, and the other to attain 400 and 20 pg-L-', respectively. Grain (rolled barley) was added monthly at 280 gmrn-2. N and P additions increased chlorophyll a accrual rates by more than an order of magnitude. Diatoms dominated the periphyton community until midsummer. In july and most of August, the relative importance of chlorophytes increased and biomass levels declined markedly in spite of continued nutrient additions. Grain additions resulted in no detectable change in periphyton accrual, but alkaline pkosphatase activity increased by 35% over control levels. These results suggest that additions of labile organic matter to nutrient-deficient coastal streams can increase autotrophic P deficiency. Based on responses of juvenile salmonids, additions of inorganic nutrients to increase autotrophic production can maximize tropkic enhancement in nutrient-deficient streams. Les auteurs ont 6tudie les taux d'accumulation et I'activit6 de la phospkatase alcaline chem le periphyton puplant des sections de la riviere Keogh (Colombie-Britannique) apr6s leapport separe de fertilisants organiques et inorganiques au printemps et 2 l'$t6 de 1981. Deux teneurs diffkrentes en RI et P ont ete uti%isees : la premiere visait une concentration ambiante respective de IV et de P de 200 et de 15 pg.L-' et la seconde, de 400 et de 26 pg*L-' respectivement. L'apprt mensuel de ckreales (flocons d'orge) s'est effectue un taux de 280 g-m-2. L'apport de N et de P a entraine une augmentation des taux d'accurnulatisn de chlorophylle a de plus d'un srdre de grandeur. Les diatom& dominaient la communaute Mriphytonique jusqu'a la mi-et6. En juillet et pendant la plus grande partie dlaoOt, l'importance relative des chlorophycopkytes a augment6 tandis que les niveaux de la biomasse ont folfernent baisd malgre l'appolf continu de bio68&nents. L'addition de cer6ales n'a pas entrain6 de variation discernable du taux d'accumulatisn du periphyton, mais I'activite de la phosphatase alcaline a augment6 de 35 % par rapport au niveau t6moin. Les rksultats portent A croire que I'apport de rnatieres organiques labiles dans des cours d'eau cbtiers pauvres en bio6l6ments p u t accroitre le deficit en P autotrophe. Dfapr&s les reactions des salmsnid6s juveniles I'apport de bio6Iements inorganiques en vue d'accrsftre la production autotrophe peut maximiser la stimulation des niveaux trophiques dans les cours d'eau pauvres en bioel6ments.
The Coho Salmon, Oncorhynchus kisutch, is one of seven species of Pacific salmon and trout native... more The Coho Salmon, Oncorhynchus kisutch, is one of seven species of Pacific salmon and trout native to northeastern Pacific Ocean watersheds. The species is typically anadromous; adults reproduce in fresh water where juveniles reside for 1-2 years before seaward migration after which the majority of growth occurs in the ocean before maturation at 2-4 years old when adults return to fresh water to spawn. Here, we report maturation of Coho Salmon in two freshwater lakes on the north coast of British Columbia apparently without their being to sea. A total of 15 mature fish (11 males and four females) were collected in two lakes across two years. The mature fish were all at least 29 cm in total length and ranged in age from three to five years old. The occurrence of Coho Salmon that have matured in fresh water without first going to sea is exceedingly rare in their natural range, especially for females. Such mature Coho Salmon may represent residual and distinct breeding populations from those in adjacent streams. Alternatively, they may result from the ephemeral restriction in the opportunity to migrate seaward owing to low water levels in the spring when Coho Salmon typically migrate to sea after 1-2 years in fresh water. Regardless of their origin, the ability to mature in fresh water without seaward migration may represent important adaptive life history plasticity in response to variable environments.
Canadian Journal of Fisheries and Aquatic Sciences, May 1, 1994
Commercial formulations of the insecticidal bacterium Bacillus thuringieresis var. kurstaki (Btk)... more Commercial formulations of the insecticidal bacterium Bacillus thuringieresis var. kurstaki (Btk) are frequently sprayed over bodies of water. The hypothesis that Btk poses a threat to stream communities was tested using streamside, flow-through mesocosms which received water and invertebrate colonists from a secondorder stream in southwestern British Columbia; low (58 BIU/ha) and high (25800 BIU/ha) treatment levels were contrasted with controls. There were no significant differences in the density or composition of benthos sampled 7 d after Btk application. The densities were highest in the high-dose mesocosms. There were no significant differences in emergence rate of adults due to treatment. During the 2.5-$8 treatment, there were marginally elevated drift rates of the mayfly Baetis when exposed to the solution, but these differences were negated during the remainder of the 24-h period. Leaf packs lose significantly more mass in controls than in high-dose mesocosrns, but there were no significant differences in the numbers of macroinvertebrates on those leaf packs. There was no evidence that addition of Btk to stream mesocosms created adverse effects for this benthic community, even at >1 08 times expected exposure rates. II arrive souvent que les formulations commerciales de la bacterie insecticide BacilBus thuringr'erpsis var. kurstaki (Btk) sont appliqukes sur des plans d'eau. Nous avons test6 I'hypothese que ie Btk constituait une menace pour [es communautes lotiques en I'essayant sur des m6socosrnes install& au bord de l'eau et aliment& en continu avec de I'eau et des organismes colonisateurs invert6br6s qui provenaient d'un cours d'eau de second ordre du sud-ouest de la Colombie-Britannique; on a compare des cas temoins a des cas A faible dose de traitement (50 BUl/haj et a forte dose de traitement (25 000 BUl/ha). BI n'y a pas eu de diff6rence significative de densit6 ou de composition du benthos echantiilonn6 sept jours apr&s B'application du Btk. Les densit6s les plus 6lev6es ont kt6 observ6es dans les m6socosmes soumis 21 un traitement 21 forte dose. Quant h I'emergence des aduites, i l n'y a pas eu de diff6rence significative attribuable au traitement. Durane les 2'5 h de traitement, il y a eu un taux ieg&rernent sup6rieur de derive des 6ph6m&res Baetis expos6es A la solution, mais ces diffkrences n'ont pas 6t6 observ6es durant la suite des 24 h. Les lots de feuilles preleves dans les stations-t6moins ont perdu beaucoup plus de biomasse que ceux des m6socosrnes exposes 2 de fortes doses de Btk; cependant, il n'y a pas eu de difference significative dans B e nombre de macro-invertebrbs observes sur ces lots. Wien n'indique que B'application de Btk h des m6socosmes lotiques a ehi des effets nuisibles sur cette communaute benthique, mGme h des concentrations > 100 fois le taux d'exposition attendu.
Part way through a year-long water quality field survey, the Capilano Reservoir, located in the G... more Part way through a year-long water quality field survey, the Capilano Reservoir, located in the Greater Vancouver Water District, was drawn down to accommodate earthquake reinforcement work on the Cleveland Dam. This paper reports observations of the effect of drawdown on water quality in the reservoir, in the context of the original study. The drawdown exposed a large zone of deltaic material through which the Capilano River eroded a path up to 2.5 m deep. The deltaic material contained substantial amounts of nitrogen and iron (TKN, 4,470 mg kg-1; total iron, 21,800 mg kg-1). During drawdown, turbidity in the reservoir increased up to 25 times as compared to prior conditions. Ammonium (NH4+-N) and dissolved and particulate iron concentrations in the drawdown zone were up to two orders of magnitude higher than concentrations upstream. Both NH4+-N and dissolved iron were observed to travel the length of the reservoir. Persistence of NH4+-N in the highly oxygenated conditions may be e...
To avoid the formation of organochlorine compounds in pulp products and effluents discharged into... more To avoid the formation of organochlorine compounds in pulp products and effluents discharged into the environment, there is a trend in the North American pulping industry to change from molecular chlorine to chlorine dioxide bleaching. However, chlorate (ClO3−) formed during chlorine dioxide bleaching is known to have toxic effects in some marine algae and has been implicated in environmental problems in the Baltic Sea. This study examined the potential effects of chlorate on natural freshwater, riverine diatom communities characteristic of many rivers in western Canada. Under low ambient river nitrate concentrations (ca. 10 µg•L−1 NO3−N), chlorate additions of up to 500 µg•L1 ClO3 did not reduce the specific growth rates (µ) or change the taxonomic composition of the attached riverine diatom community. The lack of chlorate toxicity to freshwater diatoms suggests that the nitrate uptake and/or reduction mechanism(s) of freshwater diatoms have much higher affinities for NO3 than ClO3...
Canadian Journal of Fisheries and Aquatic Sciences, 2019
The increasing rate of glacier retreat and turbid glacial runoff can have a strong influence on f... more The increasing rate of glacier retreat and turbid glacial runoff can have a strong influence on freshwater ecosystems. Seton and Anderson lakes (British Columbia, Canada) are sockeye salmon (Oncorhynchus nerka) nursery systems. Since the 1940s, the Bridge River Diversion (BRD) introduced glacially turbid water into Seton Lake. To assess the impact of the BRD on the production of Seton Lake, we combined data from limnological surveys with the analysis of subfossil cladocerans and diatoms from sediment cores, using Anderson Lake as a reference. The modern data indicate that the euphotic zone is 14 m shallower and the cladoceran density and biomass are significantly lower in Seton Lake in comparison with Anderson Lake. The paleo-data indicate that following the BRD, the sedimentary fluxes of cladoceran and diatom declined 2- to 10-fold in Seton Lake and remained low thereafter. Together, our data support declines in primary and secondary producers following the BRD, likely due to chang...
The Coho Salmon, Oncorhynchus kisutch, is one of seven species of Pacific salmon and trout native... more The Coho Salmon, Oncorhynchus kisutch, is one of seven species of Pacific salmon and trout native to northeastern Pacific Ocean watersheds. The species is typically anadromous; adults reproduce in fresh water where juveniles reside for 1–2 years before seaward migration after which the majority of growth occurs in the ocean before maturation at 2–4 years old when adults return to fresh water to spawn. Here, we report maturation of Coho Salmon in two freshwater lakes on the north coast of British Columbia apparently without their being to sea. A total of 15 mature fish (11 males and four females) were collected in two lakes across two years. The mature fish were all at least 29 cm in total length and ranged in age from three to five years old. The occurrence of Coho Salmon that have matured in fresh water without first going to sea is exceedingly rare in their natural range, especially for females. Such mature Coho Salmon may represent residual and distinct breeding populations from ...
North American Journal of Fisheries Management, 2006
An innovative coupling of nutrient addition and biomanipulation strategies was applied to Wahleac... more An innovative coupling of nutrient addition and biomanipulation strategies was applied to Wahleach Reservoir in southwestern British Columbia to successfully restore fish populations. Kokanee Oncorhynchus nerka were historically abundant in the reservoir, but the population collapsed over 2 decades. This decline in kokanee abundance and a concurrent decline in the catch rates of rainbow trout Oncorhynchus mykiss coincided with the occurrence of trophic depression in the aging reservoir. It also coincided with the onset of food competition with threespine sticklebacks Gasterosteus aculeatus that were illegally introduced in the 1970s. In 1995 through 2000, the reservoir was fertilized with liquid fertilizer with compositions of 10–34–0 and 28–0−0 at an annual P load of up to 225 mg/m2 of lake water (late May through September) at a molar N:P ratio of 25 in 1995, declining to 13 in 2000. Up to 50,000 age‐0 kokanee (up to 4.5 g) and approximately 20,000 triploid cutthroat trout O. clar...
North American Journal of Fisheries Management, 2005
Coordinated acoustic and trawl surveys were performed to locate aggregations of adult eulachon Th... more Coordinated acoustic and trawl surveys were performed to locate aggregations of adult eulachon Thaleichthys pacificus in the lower Fraser River, British Columbia, during spring 2001 and 2002. Aggregations were encountered in one portion of the study area in both years. They contained mature, spawning, and spent eulachon of both sexes, of which over 80% were spent males. These groups were 880–2,000 m long and averaged 117–140 m wide. Within them, mean fish density was 0.27–0.29 fish/m3 and species composition was 87–99% eulachon. They occurred in 6–8.5 m of water over substrate that was mainly sand with a small fraction of pea gravel. We did not determine whether these eulachon spawned in that area or had congregated there for another purpose, such as holding or migration. Other species occasionally encountered in appreciable numbers were juvenile pink salmon Oncorhynchus gorbuscha and chum salmon O. keta. Mean in situ target strengths of eulachon were −53.3 dB at 123 kHz and −50.3 d...
An on-site continuous-flow trough mesocosm was used to examine changes in the composition and abu... more An on-site continuous-flow trough mesocosm was used to examine changes in the composition and abundance of periphytic algae and benthic invertebrates from additions of a solution of treated acid mine drainage (AMD). Five control and five treatment troughs supported an assemblage of periphyton and invertebrates that colonized from water withdrawn from Foxy Creek, a stream that receives limed AMD from the Equity Silver Mine, central British Columbia, Canada. A water intake for the mesocosm was located upstream of the AMD discharge. The treated AMD was delivered to the apparatus through a pipeline laid in a canal that carried the AMD to Foxy Creek. After three weeks of colonization in the troughs, additions of one part AMD to 10 parts Foxy Creek water was delivered to the treatment troughs and continued for three weeks. Analyses of variance of measurements of abundance and biomass indexes contained high power values and indicated that the AMD addition did not significantly change the algal and insect composition and abundance. Advantages and disadvantages of the mesocosm with regard to the relative sensitivity of the measured parameters for use in examining effects of the AMD additions are discussed. The conclusion was that quantitative on-site experimentation using the mesocosm apparatus is a powerful approach in setting guidelines for AMD discharge mainly due to its capability of integrating ecosystem processes in experiments where hypothesis testing is possible.
Canadian Journal of Fisheries and Aquatic Sciences, 1984
Forest fertilization (435 kg urea∙ha−1) on the Mohun drainage, northern Vancouver Island, during ... more Forest fertilization (435 kg urea∙ha−1) on the Mohun drainage, northern Vancouver Island, during late fall 1979 resulted in a combined increase in urea, ammonia, and nitrate concentrations to 8000 μg N∙L−1 above control levels in streams not protected with 50-m-wide leave (i.e. unfertilized) strips and 350 μg N∙L−1 in those having leave strips. By spring 1980, dissolved nitrogen loads to Mohun Lake increased by a minimum of 55% in the largest basin and 1924% in the smallest basin. This corresponded to fertilizer losses of 2.1% of the total applied from drainages that had leave strips and up to 5.2% from those where the treatment included direct application to stream channels. Nitrogen transport was dominated by reduced nitrogen species and lasted up to 144 d. Relatively small changes in nitrate transport were attributed to low temperatures, which reduced rates of nitrification. Duringthe3-yr prior to forest fertilization, nitrogen and phosphorus were added to the lake at an N:P rati...
Canadian Journal of Fisheries and Aquatic Sciences, 1997
Additions of inorganic N and P to replicated stream mesocosms were used to test the hypothesis th... more Additions of inorganic N and P to replicated stream mesocosms were used to test the hypothesis that production of the benthic food web in the flow-controlled Nechako River, B.C., was N and P limited. N, P, and N + P additions were contrasted with controls to determine the responses of periphyton and macroinvertebrates over a 33-day period in late spring. Periphyton accrual under N + P addition was greater than two times that of the controls, and N alone produced a moderate increase. Periphyton showed relatively little response to P addition compared with controls. Macroinvertebrates, especially orthocladiine midges and mayflies, increased in density under N or N + P additions, in contrast with P additions and controls. Increased emergence rates of adult aquatic insects from the mesocosms were consistent with increases observed in benthic invertebrates. The results showed nutrient limitation of benthic productivity and that algal and benthic invertebrate responses were closely coupled. N was most limiting, but with additions of inorganic N as low as 10 µg⋅L -1 , P became limiting. The benthic invertebrates that increased most in abundance corresponded to the predominant prey in chinook salmon (Oncorhynchus tshawytscha) fry diets at the time of the experiment. Résumé : Nous avons ajouté du N et du P inorganiques dans une série de mésocosmes lotiques pour valider l'hypothèse selon laquelle la production de la chaîne alimentaire benthique dans la rivière Nechako, un cours d'eau de Colombie-Britannique à débit contrôlé, était limitée en N et en P. Les effets des ajouts de N, de P et de N + P ont été comparés à des valeurs témoins afin de déterminer les réponses du périphyton et des macroinvertébrés sur une période de 33 jours de la fin du printemps. L'accroissement du périphyton pour un ajout de N + P était plus du double que pour les témoins, et l'ajout de N seul a entraîné une augmentation modérée. Par contre, l'effet d'un ajout de P a eu relativement peu d'effet sur le périphyton. La densité des macroinvertébrés, particulièrement les chironomidés orthocladiinés et les éphéméroptères, a augmenté en cas d'ajout de N ou de N + P, mais pas en cas d'ajout de P ni dans les milieux témoins. Les taux accrus d'émergence observés chez les insectes aquatiques adultes des mésocosmes étaient conformes aux augmentations observées chez les invertébrés benthiques. Les résultats ont montré que la production benthique était limitée par les éléments nutritifs et que les réactions des algues et des invertébrés benthiques étaient étroitement liées. C'est l'azote qui était l'élément le plus limitant; pour des ajouts de N inorganique de seulement 10 µg⋅L -1 , P est devenu limitant. Les invertébrés benthiques dont l'abondance a le plus augmenté correspondaient aux principales proies des alevins du saumon quinnat (Oncorhynchus tshawytscha) au moment de l'expérience. [Traduit par la Rédaction]
Canadian Journal of Fisheries and Aquatic Sciences, 1990
Nutrient concentrations, periphyton standing crop and size of steelhead trout (Oncorhynchus mykis... more Nutrient concentrations, periphyton standing crop and size of steelhead trout (Oncorhynchus mykiss) and coho salmon (O, kisutch) fry increased after the fertilization of a nutrient-deficient stream with inorganic phosphorus (P) and nitrogen (N). Whole-river fertilization of the Keogh River, British Columbia, during 1983–86 to increase summer average nutrient concentrations from < 1 μg P∙L−1 and 25 μg N∙L−1 to 10–15 μg P∙L−1 and 30–100 μg N∙L−1 resulted in five- to 10-fold increases in periphyton standing crops on artificial substrata and 1.4- to 2.0-fold increases in late-September salmonid fry weights. Diatoms and chlorophytes dominated the algal periphyton on artificial substrata at fertilized sites. Cyanophytes were unimportant despite low N:P ratios in some cases. Juvenile salmonids fed primarily on benthic insects. These results suggest that autochthonous primary production can be an important energy source in forested, middle-order streams, and indicate that the manipulatio...
Canadian Journal of Fisheries and Aquatic Sciences, 1987
Periphyton accumulation rates and alkaline phosphatase activity were examined in reaches of the K... more Periphyton accumulation rates and alkaline phosphatase activity were examined in reaches of the Keogh River, British Columbia, following additions of grain and inorganic fertilizer as separate treatments during spring–summer 1981. Two different levels of N and P addition were used: one to attain ambient N and P concentrations of 200 and 15 μg∙L−1, respectively, and the other to attain 400 and 20 μg∙L−1, respectively. Grain (rolled barley) was added monthly at 280 g∙m−2. N and P additions increased chlorophyll a accrual rates by more than an order of magnitude. Diatoms dominated the periphyton community until midsummer. In July and most of August, the relative importance of chlorophytes increased and biomass levels declined markedly in spite of continued nutrient additions. Grain additions resulted in no detectable change in periphyton accrual, but alkaline phosphatase activity increased by 35% over control levels. These results suggest that additions of labile organic matter to nutr...
Canadian Journal of Fisheries and Aquatic Sciences, 1994
Commercial formulations of the insecticidal bacterium Bacillus thuringiensis var. kurstaki (Btk) ... more Commercial formulations of the insecticidal bacterium Bacillus thuringiensis var. kurstaki (Btk) are frequently sprayed over bodies of water. The hypothesis that Btk poses a threat to stream communities was tested using streamside, flow-through mesocosms which received water and invertebrate colonists from a second-order stream in southwestern British Columbia; low (50 BIU/ha) and high (≥ 5000 BIU/ha) treatment levels were contrasted with controls. There were no significant differences in the density or composition of benthos sampled 7 d after Btk application. The densities were highest in the high-dose mesocosms. There were no significant differences in emergence rate of adults due to treatment. During the 2.5-h treatment, there were marginally elevated drift rates of the mayfly Baetis when exposed to the solution, but these differences were negated during the remainder of the 24-h period. Leaf packs lost significantly more mass in controls than in high-dose mesocosms, but there we...
Page 1. BULLETIN OF MARINE SCIENCE. 55(2-3): 1160-1180. 1994 DEBRIS STRUCTURE PLACEMENTS AND WHOL... more Page 1. BULLETIN OF MARINE SCIENCE. 55(2-3): 1160-1180. 1994 DEBRIS STRUCTURE PLACEMENTS AND WHOLE-RIVER FERTILIZATION FOR SALMONIDS IN A LARGE REGULATED STREAM IN BRITISH COLUMBIA ...
Transactions of the American Fisheries Society, 2003
... Transactions of the American Fisheries Society , 124: 857872. [Taylor &amp;amp; Francis ... more ... Transactions of the American Fisheries Society , 124: 857872. [Taylor &amp;amp; Francis Online], [Web of Science ®], [CSA] View all references). ... View all references; Desloges and Church 198910. Desloges, JR and Church, M. 1989. ...
Uploads
Papers by Chris Perrin