Estimating the Effects of Environmental Variables and Gear Type on Panfish Catch and Bycatch in Reservoirs

Abstract

Panfish populations create some of the most popular and intensively managed recreational fisheries in North America. However, sampling biases may prevent fisheries managers from making informed decisions. Typically, panfish are collected using fyke nets; however, hoop nets also may be effective for capturing these species. Information regarding the most efficient and least biased approach for sampling panfish would allow fishery managers to collect the highest quality data for their management. We used three gear types (standard North American-design fyke net, 13-mm-mesh hoop nets, and 25-mm-mesh hoop nets) to compare the catch rates and size structure of panfish (Bluegill Lepomis macrochirus, Redear Sunfish L. microlophus, and White Crappie Pomoxis annularis), total bycatch, effects of environmental factors on catch and bycatch, and sampling efficiency (number of nets needed to achieve a relative SE ≤ 25% [RSE25]). Target panfish species dominated the catch (91-94%) and nontarget bycatch rates were low (6-9%) irrespective of gear type. We observed considerable variability in relative abundance, size structure, and number of nets needed to achieve RSE25, which differed by species and gear type. Detection probabilities for Bluegill and White Crappie were greatest when using 13-mm-mesh hoop nets, but detection probabilities for Redear Sunfish did not differ across gear types. Environmental variables influenced panfish detection and abundance, as lower water temperature and increased depth generally resulted in decreased detection probabilities and abundance of target panfish. The standard fyke net captured panfishes at greater rates and of broader size structures than both hoop-net designs and appeared to be the most efficient method for collecting Bluegill, Redear Sunfish, and White Crappie in this study. While hoop nets have great utility for sampling panfishes, they may not efficiently capture enough fish in some cases to support informed management decisions.

Using Bayesian multispecies models to evaluate fish and invertebrate detection probability and distribution in the hypersaline Bahia Grande tidal basin

“…These models provided a flexible framework for incorporating multiple sources of uncertainty and considering complex data structures, such as dependence between different sampling locations and multiple species (Kirsch and Peterson 2014;Stewart and Long 2016;Stewart et al 2018). By using hierarchical Bayesian models, we were able to account for individual species-specific patterns and simultaneously describe how occupancy and the probability of detection were influenced by multiple habitat variables (Stewart et al 2018;Porta et al 2020). The results obtained from these models provided robust and meaningful estimates of the relationships, which was crucial in understanding the impact of habitat variables on species richness.…”

“…2018; Porta et al. 2020). The results obtained from these models provided robust and meaningful estimates of the relationships, which was crucial in understanding the impact of habitat variables on species richness.…”

A Comparison of Two Methods for Sampling Bluegill and Redear Sunfish in Small Impoundments

“…In both studies, fyke nets captured larger lepomids than boat electrofishing (Schultz and Haines 2005;Porreca et al 2013). However, Largemouth Bass electrofishing is usually conducted during spring (Kosa and Hale 1998;Schultz and Haines 2005;Patterson 2014) and fyke nets are often set for crappies during the fall (Boxrucker and Ploskey 1989;Fischer et al 2010;Koch et al 2014;Krogman 2019;Porta et al 2020). If lepomids can be effectively sampled concurrently to crappies or Largemouth Bass using one of these approaches, it would improve sampling efficiency in small impoundments, which is critical for natural resources agencies that face shrinking budgets and increasing staff demands (Boxrucker 1997).…”