Comparison of an Active and a Passive Age-0 Fish Sampling Gear in a Tropical Reservoir

Age-0 fish sampling is an important tool for predicting recruitment success and year-class strength of cohorts in fish populations. In Puerto Rico, limited research has been conducted on age-0 fish sampling with no studies addressing reservoir systems. In this study, we compared the efficacy of passively-fished light traps and actively-fished push nets for sampling the limnetic age-0 fish community in a tropical reservoir. Diversity of catch between push nets and light traps were similar, although species composition of catches differed between gears (pseudo-F = 32.21, df =1,23, P < 0.001) and among seasons (pseudo-F = 4.29, df = 3,23, P < 0.006). Push-net catches were dominated by threadfin shad (Dorosoma petenense), comprising 94.2% of total catch. Conversely, light traps collected primarily channel catfish (Ictalurus punctatus; 76.8%), with threadfin shad comprising only 13.8% of the sample. Light-trap catches had less species diversity and evenness compared to push nets, consequently their efficiency may be limited to presence/ absence of species. These two gears sampled different components of the age-0 fish community and therefore, gear selection should be based on research goals, with push nets an ideal gear for threadfin shad age-0 fish sampling, and light traps more appropriate for community sampling. The use of both gears concurrently would give a more complete picture of age-0 fish communities, as well as help to alleviate existing selectivity biases.

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