Joseph Luczkovich
East Carolina University, Biology, Faculty Member
By using a remotely controlled autonomous vehicle ("Blackbeard" the Acoustic Wave Glider), the authors made recordings of sounds produced by striped cusk eels, sea robins, oyster toadfish, weakfish, red drum, spotted seatrout,... more
By using a remotely controlled autonomous vehicle ("Blackbeard" the Acoustic Wave Glider), the authors made recordings of sounds produced by striped cusk eels, sea robins, oyster toadfish, weakfish, red drum, spotted seatrout, bottlenose dolphins, and humpback whales in Onslow Bay, North Carolina. The article describes the wave glider, the sound recording system used on the wave glider, and presents data recorded along the track followed by the glider mission in August 2017.The National Science Foundation Major Research Instrumentation Grant (1429315), East Carolina University (ECU) Division of Research and Economic Development and Engagement (REDE), The ECU Thomas Harriot College of Arts and Science, The ECU Department of Biology, The ECU Department of Physics, and ECU Institute for Coastal Science and Policy (ICSP)
Data collected by the acoustic wave glider Blackbeard on Mission 6 in Onslow Bay 2017-08-01 to 2017-08-09.
Powerpoint file from presentation given at the meeting. This file includes several embedded videos.
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References Connaughton, M.A., and Taylor M.H. (1995). “Seasonal and daily cycles in sound production associated with spawning in the weakfish, Cynoscion regalis.” Env. Biol. Fishes 42, 233–240. Holt, S. A. (2008). “Distribution of Red... more
References Connaughton, M.A., and Taylor M.H. (1995). “Seasonal and daily cycles in sound production associated with spawning in the weakfish, Cynoscion regalis.” Env. Biol. Fishes 42, 233–240. Holt, S. A. (2008). “Distribution of Red Drum Spawning Sites Identified by a Towed Hydrophone Array”. Trans. Am. Fish. Soc., 137, 551-561. Luczkovich, J. J., Rulifson, R.A., Sprague M.W. (In Press). “Listening to Ocean Life: Monitoring Fish, Marine Mammal Sounds with Wave Glider.” Sea Technology. Luczkovich, J.J., Pullinger, R. C., Johnson, S. E. and Sprague, M. W. (2008). “Identifying Sciaenid Critical Spawning Habitats by the Use of Passive Acoustics”. Trans. Am. Fish. Soc. 137, 576–605.
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The National Science Foundation Major Research Instrumentation Grant (1429315), East Carolina University (ECU) Division of Research and Economic Development and Engagement (REDE), The ECU Thomas Harriot College of Arts and Science, The... more
The National Science Foundation Major Research Instrumentation Grant (1429315), East Carolina University (ECU) Division of Research and Economic Development and Engagement (REDE), The ECU Thomas Harriot College of Arts and Science, The ECU Department of Biology, The ECU Department of Physics, and ECU Institute for Coastal Science and Policy (ICSP).
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Male oyster toadfish (Opsanus tau) produce boatwhistle sounds to attract females to shelters in shallow water estuaries. Calls are produced in a natural soundscape that include snapping shrimp (Alpheidae sp.) and bottlenose dolphin... more
Male oyster toadfish (Opsanus tau) produce boatwhistle sounds to attract females to shelters in shallow water estuaries. Calls are produced in a natural soundscape that include snapping shrimp (Alpheidae sp.) and bottlenose dolphin (Tursiops truncatus, toadfish predators) sounds. The purpose of this study is to determine if soundscape alterations from vessels and predators cause acoustic disturbance in toadfish courtship calling behavior. Six sound types were played to toadfish in shelters positioned at 1 m from an underwater speaker: snapping shrimp sounds (Shrimp, control), low-frequency (LFDolphin) and high-frequency (HFDolphin) bottlenose dolphin biosonar, inboard (Inboard) and outboard motorboat (Outboard) noises, and a combination of vessel and predator sounds (Both). Toadfish calling rates were quantified in 600 s intervals before, during, and after noise exposure and an ANOVA was used to compare mean rates. Playback type and site (noisy vs quiet) significantly influenced toadfish calling rates (F ...
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The question we addressed in this study is whether oyster toadfish respond to vessel disturbances by calling less when vessels with lower frequency spectra are present in a sound recording and afterward. Long-term data recorders were... more
The question we addressed in this study is whether oyster toadfish respond to vessel disturbances by calling less when vessels with lower frequency spectra are present in a sound recording and afterward. Long-term data recorders were deployed at the Neuse (high vessel-noise site) and Pamlico (low vessel-noise site) Rivers. There were many fewer toadfish detections at the high vessel-noise site than the low-noise station. Calling rates were lower in the high-boat traffic area, suggesting that toadfish cannot call over loud vessel noise, reducing the overall calling rate, and may have to call more often when vessels are not present.
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This introduction covers the main components of coastal and estuarine food webs along with the selected examples of such systems. The food web is instrumental in the structuring of the system and the pathways for the transfer of energy... more
This introduction covers the main components of coastal and estuarine food webs along with the selected examples of such systems. The food web is instrumental in the structuring of the system and the pathways for the transfer of energy provide the routes along which other substances, including contaminants, are passed. The contributions emphasise not just the functional roles in the system and their importance, but also the problems faced, particularly in terms of anthropogenic pressures. An understanding of how these systems work is vital for sustainable development.
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Fishes hear and produce a variety of sounds that allow them to interpret their environment as well as communicate with their conspecifics. Some sounds are incidental sounds made while swimming and feeding. Other sounds are signals... more
Fishes hear and produce a variety of sounds that allow them to interpret their environment as well as communicate with their conspecifics. Some sounds are incidental sounds made while swimming and feeding. Other sounds are signals associated with feeding, predator avoidance, territory defense, reproduction, and echolocation. Of these sounds, one of the most pervasive is when males make advertisement sounds to communicate their readiness to spawn, as found especially in the families Sciaenidae, Gadidae, and Batrachoididae. Sounds may provide information to the listener on the behaviors, sex, or size of the fish, allowing scientists to use sound to better understand the fish behavior.
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The goal of this study was to develop a passive acoustic survey protocol to identify spawning habitats of sciaenid fishes. Based on comparisons of recordings of captive-fish and field recordings of species-specific courtship sounds,... more
The goal of this study was to develop a passive acoustic survey protocol to identify spawning habitats of sciaenid fishes. Based on comparisons of recordings of captive-fish and field recordings of species-specific courtship sounds, spawning areas of red drum, weakfish, spotted sea trout, and silver perch (Family Sciaenidae) have been identified in Pamlico Sound, NC. Sciaenid sounds were recorded using either a portable hydrophone deployed from a boat or timer-operated sonobuoys. Loudness of mating choruses of weakfish and silver perch was strongly correlated with the abundance of pelagic sciaenid-type eggs, suggesting that these areas were used for spawning. Sonobuoy recordings showed that weakfish spawned only in the high-salinity habitats near the inlets, spotted sea trout spawned predominantly in the low-salinity areas near the river mouths, silver perch spawned in both high- and low-salinity areas, and red drum spawned most commonly in low-salinity areas, but only in September....
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Ciguatoxin fish poisoning (CFP) is caused by the consumption of tropical and subtropical fishes and other marine species with high levels of ciguatoxin (CTX) in their tissues. CTX is a polycyclic neurotoxin produced by single-celled,... more
Ciguatoxin fish poisoning (CFP) is caused by the consumption of tropical and subtropical fishes and other marine species with high levels of ciguatoxin (CTX) in their tissues. CTX is a polycyclic neurotoxin produced by single-celled, photosynthetic dinoflagellates in the Gambierdiscus and Fukuyoa genera which are found in close association with benthic autotrophs. CTX enters the food web when these dinoflagellates are inadvertently consumed by herbivores grazing on their preferred substrates. The toxin biomagnifies up the food chain to the top predators and if humans consume seafood with high levels of CTX it can cause a variety of flu-like symptoms. The best way to avoid CFP is to avoid toxic fishes. However, CTX is undetectable by physical inspection. This study investigated local fishers’ knowledge of ciguatera hotspots and coldspots along Puerto Rican coral reefs using toxic-dinoflagellate cell counts and by estimating fish toxicity in those sites using a cell-based Neuro-2a cyt...
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Most passive acoustic studies of the soundscape rely on fixed recorders, which provide good temporal resolution of variation in the soundscape, but poor spatial coverage. In contrast, a mobile recording device can show variation in the... more
Most passive acoustic studies of the soundscape rely on fixed recorders, which provide good temporal resolution of variation in the soundscape, but poor spatial coverage. In contrast, a mobile recording device can show variation in the soundscape over large spatial areas. We used a Liquid Robotics SV2 wave glider fitted with a tow body with a passive acoustic recorder and hydrophone, to survey and record the soundscape of the Atlantic Ocean off North Carolina (United States). Recordings were analyzed using power spectral band (PSB) sums in frequencies associated with soniferous fish species in the families Sciaenidae (drums and croakers), Ophidiidae (cusk-eels), Batrachoididae (toadfish), Triglidae (sea robins), and Serranidae (groupers). PSB sums were plotted as the wave glider moved offshore and along the coast, came back inshore, and circled artificial and natural reefs. The soundscape in water <20 m was dominated by nocturnal fish choruses with PSB sums > 120 dB re 1 μPa2:...
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Underwater sounds include steady-state vessel noise, tran-sient animal calls, and impulsive pile driving sounds. We developed a finite difference time domain (FDTD) model
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ABSTRACT Bottom trawling captures shrimp and a large number of non-target fish and invertebrate species (by-catch). Although 11,700 trawling trips have been recorded in Core Sound in areas open to trawling since 2001, this number has... more
ABSTRACT Bottom trawling captures shrimp and a large number of non-target fish and invertebrate species (by-catch). Although 11,700 trawling trips have been recorded in Core Sound in areas open to trawling since 2001, this number has recently been declining to low levels. We used biological sampling and harvests from the North Carolina Division of Marine Fisheries to construct ECOPATH models of trawling impacts and other gears in Core Sound. We explored some of the ecosystem differences between open and closed areas using ECOPATH model outputs and predict the future of shrimp trawling using ECOSIM. We examined ECOSIM scenarios that included lower shrimp trawling, a gill net ban, and increased salinity due to climate change. Net primary production computed in ECOPATH was greater in the open trawling areas. Reduced shrimp trawling will produce more jellyfish, flounders, and shrimp. A gill net ban will increase the biomass of striped mullet, sharks, flounders and red drum. Climate change will increase salinities, leading to more shrimp biomass. ECOPATH models allow exploration of indirect impacts.
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Fishes and marine mammals make sounds and listen for predators and conspecifics, i.e., they communicate underwater using sound. Longspine squirrelfish Holocentrus rufus are nocturnal reef fishes living in the Caribbean that commonly... more
Fishes and marine mammals make sounds and listen for predators and conspecifics, i.e., they communicate underwater using sound. Longspine squirrelfish Holocentrus rufus are nocturnal reef fishes living in the Caribbean that commonly produce low-frequency sounds at dawn and dusk. In order to determine the reactions of longspine squirrelfish to sounds made by their conspecifics and by their potential predators, we performed experiments in which we played the grunting sounds of longspine squirrelfish and the echolocation and signature whistle sounds of bottlenose dolphin Tursiops truncatus through an underwater speaker on the reef at the Institute for Marine Studies, Calabash Caye, Turneffe Atoll, Belize. At the surface, a portable laptop computer was programmed to playback a series of sounds in the following sequence: preplayback period with no sounds (8 min in experiment 1, 5 min in experiment 2), 700-Hz tone (10 min), longspine squirrelfish grunts (10 min), bottlenose dolphin echolo...
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Trawling has been shown to cause high mortality of discarded species (bycatch) and short-term ecological disturbance to bottom communities in coastal systems, resulting in lowered benthic biomass. Here we report evidence of a... more
Trawling has been shown to cause high mortality of discarded species (bycatch) and short-term ecological disturbance to bottom communities in coastal systems, resulting in lowered benthic biomass. Here we report evidence of a trawling-induced trophic cascade resulting in an increase in biomass of benthic polychaetes after the end of the shrimp trawling season in areas open to trawling in North Carolina (USA). Using comparative measurements of abundance of bycatch species and benthos in open and closed trawling management areas and Ecopath network modeling, we show that trawling in the open area has led to increases in deposit-feeding polychaetes and decreases in bycatch species (fish and crabs) that are benthic predators on the polychaetes. We conclude that proposed management actions to reduce the shrimp trawl fishery effort will influence other net and trap fisheries for southern flounder and blue crabs indirectly, as revealed by our network models, and the proposed trawling ban m...
ABSTRACT A core question in ecology concerns the relative functional importance of species in communities and ecosystems. This information is useful for fisheries management as it can identify ecosystem components relevant for managing... more
ABSTRACT A core question in ecology concerns the relative functional importance of species in communities and ecosystems. This information is useful for fisheries management as it can identify ecosystem components relevant for managing target species. Here, we apply the centrality concept from social network analysis to characterize the relative importance of species in the food web of Core Sound, NC. Specifically, we apply Hubbell&#39;s measure of influence and an ecological derivative called Throughflow Centrality to compare the ecosystem structure between regions with and without trawling. Both centrality measures consider direct and indirect influences, and thus provide a holistic perspective. Our results show ecosystem functional change likely due to this difference fisheries management.
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There is little disagreement among regulators, scientists, and other interested parties as to the complexity surrounding our understanding of the potential and realized impacts of anthropogenic noise on marine life. Given the challenges... more
There is little disagreement among regulators, scientists, and other interested parties as to the complexity surrounding our understanding of the potential and realized impacts of anthropogenic noise on marine life. Given the challenges of research in an aquatic environment, the breadth of species of interest and the range of human-made noise-producing activities, it is difficult at best to identify the most important science needs that improve our understanding and ultimately regulation of the issue.
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Bottom trawling captures shrimp and a large number of non-target fish and invertebrate species (by-catch). Although 11,700 trawling trips have been recorded in Core Sound in areas open to trawling since 2001, this number has recently been... more
Bottom trawling captures shrimp and a large number of non-target fish and invertebrate species (by-catch). Although 11,700 trawling trips have been recorded in Core Sound in areas open to trawling since 2001, this number has recently been declining to low levels. We used biological sampling and harvests from the North Carolina Division of Marine Fisheries to construct ECOPATH models of trawling impacts and other gears in Core Sound. We explored some of the ecosystem differences between open and closed areas using ECOPATH model outputs and predict the future of shrimp trawling using ECOSIM. We examined ECOSIM scenarios that included lower shrimp trawling, a gill net ban, and increased salinity due to climate change. Net primary production computed in ECOPATH was greater in the open trawling areas. Reduced shrimp trawling will produce more jellyfish, flounders, and shrimp. A gill net ban will increase the biomass of striped mullet, sharks, flounders and red drum. Climate change will i...
Core Sound, North Carolina, is an inshore estuarine area composed of nursery areas (closed to trawling) as well as waters open to trawling, creating an opportunity to study the ecological network impacts of commercial shrimp trawling. We... more
Core Sound, North Carolina, is an inshore estuarine area composed of nursery areas (closed to trawling) as well as waters open to trawling, creating an opportunity to study the ecological network impacts of commercial shrimp trawling. We used field collections, fisheries data from the NC Trip Ticket program, and Ecopath with Ecosim 6 to create four models of areas Open and Closed to commercial shrimp trawling during the Spring and Fall. Each model consisted of 65 compartments, ranging from detritus to birds, and four different fisheries (crab pots, gill nets, haul seines, and pound nets). Two additional gear types, shrimp trawls and skimmer trawls, and an additional compartment (bycatch), were included only in the Open models. Comparisons of biomass (gC/m2) for common bycatch species (such as pinfish, spot and croaker) indicated greater biomass in areas closed to trawling, and comparisons of infaunal benthic invertebrates, especially polychaetes, indicated greater biomass in areas o...
We have been collecting biological data for the construction of a food web model of Calabash Caye, Belize using Ecopath with Ecosim software. Characterization of the mangrove, seagrass and coral reef environments surrounding Calabash Caye... more
We have been collecting biological data for the construction of a food web model of Calabash Caye, Belize using Ecopath with Ecosim software. Characterization of the mangrove, seagrass and coral reef environments surrounding Calabash Caye will provide baseline data for a network model of the trophic relationships in this area, which is currently being considered as a marine protected area. Our Ecopath model follows a previously published Puerto Rico – Virgin Islands 50-compartment model; 27 of the compartments represent fishes. The collection of fish biomass and abundance data was done using visual surveys with both SCUBA and snorkel. Important dietary information was gathered from fish collected by spearfishing, beach seine, gill nets and hook and line. Smaller benthic invertebrates were collected using a small suction dredge and larger invertebrates were counted along visual transects using SCUBA and snorkeling. Additional data for various compartments that were not sampled, inclu...
Carboxymethylcellulase (CMCase)-producing obligate anaerobes were isolated from the intestinal tract contents but not the feeding habitat of seagrass-consuming pinfish. Taxonomic characterization of these CMCase-producing strains revealed... more
Carboxymethylcellulase (CMCase)-producing obligate anaerobes were isolated from the intestinal tract contents but not the feeding habitat of seagrass-consuming pinfish. Taxonomic characterization of these CMCase-producing strains revealed four taxonomic clusters; three were clostridial and one was of unknown taxonomic affinity. Our results demonstrated that the CMCase-producing obligate anaerobe community from pinfish differed from functionally similar microbial communities in terrestrial herbivores.
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ABSTRACT Automated acoustic recording stations are being considered to allow managers to monitor remote coral reefs. Sounds of interest include those of biological, environmental, and anthropogenic origin. Preliminary data about remote... more
ABSTRACT Automated acoustic recording stations are being considered to allow managers to monitor remote coral reefs. Sounds of interest include those of biological, environmental, and anthropogenic origin. Preliminary data about remote acoustic monitoring of reefs were obtained in February–March of 2001 and 2002 during National Oceanic and Atmospheric Administration (NOAA) cruises to the Phoenix and Line Islands in the western Pacific Ocean. In 2001, sonobuoys manufactured by East Carolina University (ECU) were deployed to make a 90‐s acoustic recording every hour for a 24‐h period at each location. In 2002, continuous 24‐h acoustic recordings were made using an experimental Remote Underwater Digital Acoustic Recording (RUDAR) system. The ECU sonobuoys recorded diurnal and locational variations in the sounds of snapping shrimp as well as variations in ambient noise. At most locations, the snapping shrimp sound level increased near sunset and decreased near sunrise. The experimental RUDAR system recorded limited data due to some technical problems arising from field use. Analysis of the recordings as well as recommendations for future studies will be presented.
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ABSTRACT Passive acoustic monitoring can be a useful tool to include on Ocean Observing Systems. As an example, we describe the monitoring the acoustic environment in the coastal waters of North Carolina (USA) using an instrumented... more
ABSTRACT Passive acoustic monitoring can be a useful tool to include on Ocean Observing Systems. As an example, we describe the monitoring the acoustic environment in the coastal waters of North Carolina (USA) using an instrumented platform. The ECU Itpod (instrumented tripod) has been deployed in several locations in Pamlico Sound and river estuaries since 2006 to study fishes in the Family Sciaenidae (drums and croakers). We will present data recorded with hydrophones deployed on the Itpod with remote data loggers, acoustic Doppler current profilers, turbidity meters and water quality instruments. We have used passive acoustic recordings to study the correlations of fish sounds and environmental parameters (temperature, salinity, turbidity, dissolved oxygen, wave action, river discharge, tropical storms). The long-term data suggest that spring temperature increases are associated with increased activity of acoustically mediated courtship and spawning behavior of sciaenid fishes; these sounds decline in the fall as water temperature declines. In addition, we have observed acoustic interactions between marine mammal predators and their fish prey and the effects of noise from tugs and small boats on fish sound production. Itpods must be recovered periodically to recover data and replenish batteries; solar-powered platforms and automated fish detection algorithms are under development.
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ABSTRACT Passive acoustic monitoring is a useful tool for studying soniferous fishes in shallow water estuaries. We have used a variety of techniques for monitoring the acoustic environment in the coastal waters of North Carolina (USA) to... more
ABSTRACT Passive acoustic monitoring is a useful tool for studying soniferous fishes in shallow water estuaries. We have used a variety of techniques for monitoring the acoustic environment in the coastal waters of North Carolina (USA) to study fishes in the Family Sciaenidae (drums and croakers), which produce sounds with frequencies below 1000 Hz. We will present data recorded with hydrophones deployed from a small boat, a hydrophone array towed behind a boat, and remote data loggers. We have used passive acoustic recordings to study the distributions (large- and small-scale) and seasonality of acoustically active courtship and spawning behavior, acoustic interactions between predators and prey, the effects of noise from tugs and small boats on fish sound production, and relationships between fish sound production and environmental parameters such as temperature and salinity. One limitation on shallow-water acoustic monitoring is the sound propagation cutoff frequency, which depends on the water depth. All frequency components below the cutoff frequency decay exponentially with propagation distance. This limit on shallow-water sound propagation must be considered when selecting locations for acoustic monitoring and comparing recordings made in waters of different depths. We will explore the implications on acoustic monitoring due to the cutoff frequency.
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Reef fishes produce sounds in response to disturbance, during agonistic encounters in defense of territories, and in spawning events. We recorded in captivity the disturbance sounds of reef fishes in the grunt family (Haemulidae),... more
Reef fishes produce sounds in response to disturbance, during agonistic encounters in defense of territories, and in spawning events. We recorded in captivity the disturbance sounds of reef fishes in the grunt family (Haemulidae), triggerfish family (Balistidae), and ...
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ABSTRACT Carnivorous juveniles (&lt;16 mm LS) of pinfish Lagodon rhomboides apparently lacked gastric glands in the stomach while larger fish, intermediates (30-33 mm LS) and herbivorous adults (&gt;80 mm LS) had numerous gastric... more
ABSTRACT Carnivorous juveniles (&lt;16 mm LS) of pinfish Lagodon rhomboides apparently lacked gastric glands in the stomach while larger fish, intermediates (30-33 mm LS) and herbivorous adults (&gt;80 mm LS) had numerous gastric glands. Two cell types were identified in the gastric glands of larger fish: mucous secreting cells and secretory cells which had ultrastructure features typical of digestive enzymes and acid secretion. Lipid absorption occurred throughout the caeca and intestine in all sizes of fish. Microvilli found on the rectal epithelial cells of the intermediate and adult pinfish occurred on stalks and were possibly associated with water reabsorption. Liver enzyme activities changed in small fish (26–39 mm LS) compared to the adult fish. Alanine amino transferase (ALT) and fructose diphosphotase (FDP) activities declined while pyruvate kinase (PK) activities increased significantly. These changes were consistent with a change in diet from a carnivorous (high protein) diet in juveniles to an omnivorous (lower protein) diet determined by stomach content analyses.
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Research Interests: Treatment, Network Analysis, Animal communication, Biological Sciences, Impact Analysis, and 13 moreEnvironmental Sciences, Models, Food web, Trophic Cascade, Trophic Level, Low Power, Ecosystem, Structural Complexity, Indexation, Network Model, Experimental Measurement, Stomach Content, and High density
ABSTRACT Selective feeding by fishes may be due in part to the conspicuousness of particular prey types; certain prey may be disproportionately detected by fish and thus could be subject to a greater risk of predation. In laboratory... more
ABSTRACT Selective feeding by fishes may be due in part to the conspicuousness of particular prey types; certain prey may be disproportionately detected by fish and thus could be subject to a greater risk of predation. In laboratory experiments designed to test the relative importance of chemoreception, vision, and prey activity in the process of prey detection, I allowed pinfish Lagodon rhomboides (Linnaeus) to choose among various seagrass-meadow-associated infaunal and epifaunal prey [Melita, Cerapus, Caprella (amphipods); Hippolyte (shrimp); Americonuphis, Nereis (polychaetes); and Clytia, Sertularia (hydroids)]. In laboratory trials, pinfish approached individual prey enclosed in clear glass tubes with an open end (covered with 50-μm mesh Nitex screen to allow water exchange) that were provided with sand and seagrass blade substrata. Within each trial, one prey species was offered in an array consisting of an unaltered tube and tubes that had been manipulated to prevent detection of the enclosed prey using vision (opaque sides), olfaction (sealed tops), or both senses (opaque sides and sealed top). Pinfish most frequently approached prey in the clear-sided, screen-topped tubes and least frequently approached tubes with opaque sides and sealed tops; the tubes with sealed tops and clear sides or screened tops and opaque sides were approached with intermediate frequency. Approach frequencies were similar for all prey types tested. It appears that vision and chemoreception were used jointly by pinfish to locate the enclosed prey. In a second series of prey choice experiments, pinfish were offered four prey types (amphipods, shrimp, polychaetes, and hydroids), either live or freshly killed, in clear glass tubes with screen tops to determine if inactive, but otherwise similar prey, were approached as frequently as active prey. All prey types tested were approached with similar frequency; however, live prey were approached more frequently than dead prey (although not significantly more frequently). Small, mobile epifaunal prey (i.e., amphipods and other microcrustaceans) should be disproportionately detected on the seagrass blades by pinfish in the field and thus may be subject to a greater risk of predation than sessile prey.