Comparison of sinking and floating gill nets for collecting shads (Dorosoma spp.) in shallow Florida lakes

Abstract

We compared the catch rate and size structure of shads (Dorosoma spp.) collected in floating and sinking experimental gill nets to determine which net type would be more appropriate for the long-term monitoring of these species in Florida lakes. We sampled 3 lakes of varying trophic states. Sinking gill nets generally yielded higher catch rates of shads than did floating gill nets, although catches were low in the mesotrophic lake regardless of net type. Furthermore, sinking nets tended to capture a wider size range of target fish and more species overall. We recommend approximately 20 sinking gill nets to adequately assess abundance and size structure of shad populations in eutrophic systems. Insufficient numbers of fish collected in the mesotrophic system, presumably due to low abundances, precluded sample size estimation based on these criteria, but we recommend approximately 10 sinking gill nets to obtain presence–absence information. Although the study lakes were chosen to provide a cross-section of lakes typically found in Florida, additional evaluations should be done for other lakes to ensure the sampling protocol will be adequate for meeting the goals of statewide monitoring of these species. Standardized sampling protocols over a wide geographic area has many benefits, but the results of this study illustrate the continued need for evaluating individual systems and, when necessary, modifying protocols to provide data that will be useful in the long-term management of target species, given specified sampling targets.