Fish diversity

1. Relationships between river flow characteristics and fish community/population dynamics (i.e.
flow–ecology relationships) underpin methods to determine and monitor environmental water allocations.
Quantifying these relationships can be difficult, and consequently, most environmental flow
strategies for fish conservation in Australian rivers are based on general flow–ecology relationships
as opposed to statistical predictions.
2. Of those studies that have investigated relationships between flow and fish, most have not
accounted for incomplete and variable detection of fish by the sampling methods, thus making the
implicit assumption that sampling efficiency is invariant. This important assumption is rarely met,
leading to inconsistent research findings and spurious results, and a reliance on generic flow–ecology
principles for defining flow management strategies.
3. We illustrate how and when detection probability varies when sampling freshwater fish and the
consequences to scientific inference about fish–flow relationships. Methods for accounting for imperfect
detection of fish are identified and tools to increase the efficiency of experimental designs while
reducing sampling cost are discussed. These tools include methods for borrowing information among
experimental components and simulation techniques to optimise sampling designs.
4. We argue that, due to the very nature of sampling designs to quantify flow–ecology relationships
(e.g. sampling at different flow magnitudes/regimes), the challenge of imperfect detectability is particularly
relevant to environmental flow science. We encourage the broader adoption of methods that
account for imperfect detection to improve inference about fish–flow relationships and increase the
successful application of environmental flows for managing fish communities.

Fish diversity in Oxbow lake is adversely impacted due to diverse anthropogenic activities like over-exploitation, indiscriminate use of fine meshed fishing gears, jute retting etc. To quantify the impact of such anthropogenic activities on fish diversity and aquatic health, a survey with seasonal analysis of diversity indices, relative frequencies and abundance status of native fish populations was conducted from April 2013 to March 2014 in a semi closed Oxbow lake in Nadia district in eastern India. The level of p<0.05 was accepted as statistical significance. Of the 33 native fish species recorded 33% belonging to 8 orders and 17 families fell under vulnerable or endangered categories. Native species like Amblypharyngodon mola, Chanda nama, Pethia ticto and Notopterus notopterus, Colisa fasciata, P. ticto, were the most dominant and frequent fishes. Shannon-Weiner diversity index was decreased by 41% by precipitating impact of monsoonal anthropogenic activities during post-monsoon. Low native fish diversity indices are pointers to poor ecosystem health status owing to intense adverse activities like jute retting, indiscriminate fishing aggravated by influx of turbid water from the river Ganga following episodic flood events during monsoon. Regulation and prevention of such anthropogenic activities are urgently warranted for sustainable conservation and management of the Oxbow lake.

This study reports on the diversity and distribution of mangrove gastropods from Kuala Selangor Nature Park sampled from August to November 2017. The line transect with quadrat method was employed to sample gastropods which were handpicked from the various mangrove structures (root, stem, branch) and mangrove floor within 5m x 5m quadrats. Nineteen gastropod taxa were recorded fr om the Bruguiera, mixed (Bruguiera, Avicennia & Rhizophora), and Avicennia & Rhizophora zones. The Ellobiidae (Elobium aurisjudae and Cassidula aurisfelis), Potamidae (Cerithedia obtusa, Cerithidea cingulata and Telescopium telescopium), Muricidae (Chicoreus capucinus) and Naticidae (Nerita balteata) were the most distributed gastropod families at the study site. Gastropod horizontal distribution varied between tree zones (Bruguiera; Bruguiera-Avicennia-Rhizophora; and Avicennia-Rhizophora) and tree type (Brugueira, Rhizophora and Avicennia), while gastropod vertical distribution varied based on height on tree (0-120cm) and sub-habitats (roots, floor and trunk) as shown by the principle components analysis (PCA) biplots. The Margalef's species richness (D=2.90) and Shannon-Weiner diversity (H'=2.32) was low which is typical of mangroves that are mature while Pielou's evenness (J=0.77) was high implying lack of dominance by specific gastropod taxa.

One year long study was executed from August 2016 to July 2017 to identify the
present status of fish species diversity of Surma River at Sylhet Sadar, Northeast Bangladesh. A total of 51 fish species belonging to 16 taxonomic families has been identified. The most abundant family was recorded as Cyprinidae covering 36%, while the least abundant family was Gobidae and Plotosidae comprising 1%. A Shannon-Weaver diversity index was fluctuated between 2 to 2.5 with mean value 2.30±0.14, which reveals exposer to light pollution in study area. The peak Pielou’s evenness index value was 2.2 in April and the lowest value 1.47 in July with mean value 1.93±0.23. Maximum value of Simpson dominance index is 7.98 in August and minimum value 5.32 in October with mean value 6.99±0.86. The catch per unit effort ranged from 0.15 to 0.48 with an average value of 0.34±0.11.

The pilot study on fish composition and diversity of Apodu reservoir, Malete, Nigeria was carried out between January to May 2017 using cast and gill net. A total number of 3333 fish, comprising 8 families and 17 species were recorded. Brycinus nurse were most dominant for the period of study contributing 29.31% and Auchenoglanis occidentalis, least abundant made up of 0.03% of total catch. Other families and there percentage contribution in the total catch were Mormyridae (34.14%); Cichlidae (15.24%); Mochokidae (14.01%); Clariidae (6.84%); Protopteridae (0.21%) and Clupeidae (0.21%). The range of physico-chemical parameters of the water body were: temperature (24.1 o C-29.8 o C); dissolved oxygen (4.4mg/l-6.00mg/l); conductivity (84.7µs/cm-105µs/cm); pH (6.63-7.97); transparency (125.7cm-191.3cm) and total dissolved solids (42ppm-69.7ppm). All values were within the limits for fish tolerance, survival and production. This establishes the species composition of the reservoir and management strategy for sustainability and conservation were suggested. 1. Introduction Reservoirs are invaluable ecological resources that serve many human needs and therefore enhance our lives by providing a lot of opportunities. This explains why a large proportion of population lives near water bodies such as reservoirs, lakes, rivers, and swamps. Many depend heavily on the resources of such water bodies as their main source of animal protein and family income [1]. The Apodu reservoir serves these purposes after construction in a way of improving water availability to the villages around it and Malete town due to water scarcity in the area. Fish are important in that they contribute as much as 17% of the world's animal protein [2]. Inland fisheries play an important role in the provision of protein to Nigerians with high population of about 178.5 million people [3] , especially when imported fish is becoming too expensive for low income earners [2]. Nigeria studies of fish biodiversity, abundance, distribution and yield of most of the inland lacustrine water bodies have been limited to large sized water bodies (greater than 1,000 ha) such as Kainji, Jebba, Shiroro, Tiga, Bakolore and Gorongo among others and some small/medium sized reservoirs [4]. One of the means of studying reservoir is to determine the fauna component especially the fish composition, distribution and diversity in respect to the abiotic component of such ecosystem [5]. A comprehensive understanding of the dynamics of a fish population is an important management tool for the sustainable exploitation of any fisheries resource. Thus, biological surveys of fish species composition and abundance are regular features in the management of fisheries [6]. The fish assemblage and the abiotic study can give an indication of the quality of water in the reservoir and helps to improve how reservoirs are essential for adequate protein intake in Nigerian diets. This study set out to determine the baseline abundance assessment and diversity of fish species in Apodu reservoir, Malete, Nigeria for the first time and their interaction with some abiotic factors of the water body. This will create baseline information on the present species for better management of the reservoir.

Assiganga stream is an important tributary of Bhagirathi River in central Himalaya (India). The stream is characterized by heterogeneity in habitat and substratum features harboring diverse fish fauna. At present this stream is facing threat of being fragmented by the construction of two hydro-electric projects. Present study aimed to study fish diversity and their habitat use in Assiganga stream. This study reports fifteen species (14 indigenous and 1 exotic) belonging to 8 genera, 4 families and 3 orders. Snow trout, Schizothorax richardsonii (Cyprinidae family) and Salmo trutta (Salmonidae family) were the dominant species (> 65% of total fish catch) throughout the entire length of stream. The presence of rich benthic food, clear water, low turbidity (01-05 NTU), high DO (8.75-10.75 mg-l), and high water velocity (1.10-1.40 m-s) with characteristic rapids and cascades in upper reaches provides ideal habitat for the existence of native snow trout and exotic trout species. Few cat fishes, loaches, Tor spp. and lesser barils also have been reported during the study.

In the 19th/early 20th eentury, overfishing eaused a drastie decline and finally extinetion of the loeal sturgeon populations in the eastern Atlantic. To date, it is not known whether it was Acipenser sturio or the primarily North Ameriean Acipenser oxyrinchus that oecurred here. The aim of the study was to show the historieal pattern of sturgeon distribution and their diversity in this area over the last 2500 years. This question is essential for international restoration programmes.

The present study was carried out to investigate the comparative seasonal distribution and relative
abundance of fish fauna of streams Bachan Gad of river Alaknanda and Kakda Gad of river Mandakini of
Mid-himalayan Ganga river System. Total length of the Bachan Gad is 14.5 km from origin to the confluence at main
river Alaknanda with an altitudinal variation from 605.94 to 1418.23m (a.s.1), whereas, total length of the Kakda Gad
is 15.5 km. from origin to confluence at main river Mandakini with altitudinal variation from 984.50 to 1993.70 m
(a.s.1). Total 23 species from Bachan Gad and 20 fish species were identified from Kakda Gad. The differences in
the availability of fish-fauna were directly related to the nature of the profile and slope of tributaries; which affects the
migration and breeding grounds of the fishes inhabited in the main river Alaknanda and Mandakini of Ganga river
system. Variation in the availability of fishes has been recorded from different sites of the stream. In streams and
rivers the changes take place along their length is directly related to the eco-physico-chemical nature (water depth,
current, substratum etc). All these factors which change along the length of streams are also the factors which
control the distribution of the various sections of the biotic fauna and flora.