Sampling Gear Efficiency and Selectivity for Juvenile Ladyfish Elops Saurus in Florida Waters (USA)

摘要

At the foundation of managing wildlife is collecting accurate field data with appropriate sampling gears and methods under a strict experimental design and standardized protocols. To elucidate, monitor, and predict wildlife patterns in space and time requires the selection of specific sampling gears for the community or species of interest, especially for species that display spatial and temporal variability in distribution and abundance. Among the most challenging types of wildlife to examine in the field are marine fisheries resources given their expansive range, spatial and temporal distribution, and specific early life-history characteristics (e.g., habitat, environmental conditions, and recruitment patterns). Numerous studies have investigated the catch efficiency for various sampling gears and techniques; however, no information has ever been reported for ladyfish (Elops saurus), an economically valuable species in the southeastern United States and other world-wide regions. Given the importance of collecting ladyfish early life-history information, the purpose of this investigation was to evaluate, for the first time, the efficiency and selectivity of various field-sampling gears used in Florida waters to collect juvenile ladyfish. The specific objectives were to examine the sampling gear efficiency and selectivity on juvenile ladyfish relative abundance and length-frequency distribution among different water bodies. This investigation found that juvenile ladyfish abundance, size, and length frequency distribution significantly varied by sampling gear. In addition, the findings revealed that the most efficient gear for sampling juvenile ladyfish smaller than 100 mm SL were seines with an offshore deployment method. Despite detecting length frequency differences among sampling gears, no clear pattern was evident among estuaries. In general, seine catch efficiency decreased and gillnet efficiency increased with ladyfish size. To alleviate gear or sampling bias, results demonstrated that researchers need to use a variety of sampling gears to sample ladyfish.