We are trying to estimate the biomass of adult snook in Brazilian estuaries where underwater visual census methods cannot be used. A method using gillnets perhaps? Thank you.
We have found methods mostly for juvenile fish, such as those listed in Rozas and Minello 1997 (Estimating Densities of Small Fishes and Decapod Crustaceans in Shallow Estuarine Habitats: A Review of Sampling Design With Focus on Gear Selection. Estuaries Vol. 20, No. 1, p. 199-213 March 1997). However any method for young adults or adults in mangrove estuaries will be most welcomed. Thank you.
Hello Alejandro,
I don't know the width of your estuaries, so I don't exactly know if it's feasible or not but you could use mark-recapture methods.You tag a significant set of individuals and you try to recapture them either with nets (gill nets, trammel nets or whatever...) or with telemetry. Then, using the lincoln Petersen equation, you can estimate your population.
Stephane
You'd probably need a long seine. Florida's Fisheries-Independent Monitoring Program uses a 183-meter seine set from the back of a shallow-draft boat ("mullet skiff") in a rectangle shape (one edge of the rectangle being the shore). Then 4 people haul it in. Great exercise! See Winner et al, for example (http://www.tandfonline.com/doi/abs/10.1577/T08-215.1). You could use a net like this in conjunction with mark and recapture to get a biomass estimate, or perhaps just do some gear efficiency studies and extrapolate. The appropriate measure of extrapolation may be length of shoreline rather than area, given the species tends to be along the shore. Hope this helps.
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