Sampling Channel Catfish with Tandem Hoop Nets in Small Impoundments

Abstract

Because populations of channel catfish Ictalurus punctatus have been difficult to sample in small impoundments, we determined whether tandem hoop net series (three nets tied in series and baited with cheese) fished for 3 d could effectively sample these populations. In 2000 we compared seasonal catch rates (catch per unit effort (CPUE), defined as the number of fish caught per series) and length frequencies (total length (TL); mm) of channel catfish captured with two types of tandem series (long versus short bridles) and monitored the mortality of channel catfish along with the CPUE and mortality of bycatch in five lakes. Mean CPUE ranged from 12 to 194 fish/series for channel catfish and from 5 to 101 fish/series for bycatch among series types, lakes, and sampling periods. Mean CPUE for channel catfish and bycatch was similar between series types and did not consistently vary with sampling period. Length frequencies of channel catfish were usually similar between series types. Mortality was low for both channel catfish (0.3% of total catch) and bycatch (8%). In 2001, using short‐bridled series, we assessed gear size bias in one lake; sampled 66 lakes that are stocked annually with channel catfish fingerlings at rates of 12, 37, or 74/ha; and estimated the sample sizes required for precise estimates of mean CPUE and accurate estimates of size structure. Hoop nets failed to capture channel catfish less than 250 mm TL in proportion to their abundance. Mean CPUE among 62 lakes ranged from 0.5 to 369.7 channel catfish/series and increased with stocking rate. Four lakes were excluded because of the high catch and mortality of turtles. Mean TL ranged from 276 to 463 mm among the lakes and decreased with stocking rate. For moderate precision (coefficient of variation (100·SE/mean) = 0.2) of mean CPUE, from 12 to nearly 50 series were required, and length measurements from 300 fish were necessary for accurate assessments of size structure. Tandem hoop netting provided adequate samples of channel catfish in most small impoundments, but obtaining precise estimates of CPUE may be difficult; moreover, turtle mortality can be problematic in some lakes.

Effect of bait and gear type on channel catfish catch and turtle bycatch in a reservoir

“…Number of samples (effort) needed to achieve two estimates of sampling precision (relative standard error (RSE)) at two levels of confidence is given. lakes sensu Michaletz & Sullivan 2002), trotlines baited with Zote TM soap appears to be a viable option for sampling channel catfish and this could be explored in future studies.…”

“…Tandem hoop nets have been gaining popularity as a means to sample channel catfish Ictalurus punctatus in reservoirs (Michaletz & Sullivan 2002;Bodine et al 2013) but it is often associated with high bycatch, particularly aquatic turtles (order Testudines). Few studies have quantified bycatch of turtles but personal experience and anecdotal evidence from other biologists have confirmed that this is an issue.…”

“…Among 18 tandem hoop net sets in Longview Lake, Missouri, Sullivan and Gale (1999) reported a total of 52 turtles as bycatch, 49 of which were dead when the nets were retrieved after 2-d sets. Michaletz and Sullivan (2002) mentioned having to remove four lakes from an analysis while trying to determine hoop net effectiveness for catching channel catfish because of 'large catches and high mortality of turtles,' later defined as 'hundreds.' Ultimately, Michaletz and Sullivan (2002) recommended avoiding the use of hoop nets in lowland lakes where large turtle populations occurred due to the degree of turtle bycatch.…”

“…Michaletz and Sullivan (2002) mentioned having to remove four lakes from an analysis while trying to determine hoop net effectiveness for catching channel catfish because of 'large catches and high mortality of turtles,' later defined as 'hundreds.' Ultimately, Michaletz and Sullivan (2002) recommended avoiding the use of hoop nets in lowland lakes where large turtle populations occurred due to the degree of turtle bycatch. In our experience, we have caught as many as 100 turtles in a single tandem hoop net set, especially during periods of drought, and most of those turtles died.…”

Accidental Bait: Do Deceased Fish Increase Freshwater Turtle Bycatch in Commercial Fyke Nets?

“…Although the study of freshwater bycatch lags far behind that of marine bycatch (Soykan and others 2008; Raby and others 2011), freshwater turtle bycatch mortality has been documented in inland commercial fisheries where passive fishing gears such as hoop, fyke, and trap nets are used (Michaletz and Sullivan 2002;Horne and others 2003;Barko and others 2004;Carrière 2007;Larocque and others 2012a). Delayed maturity, high juvenile mortality, and low adult mortality are life-history characteristics that make turtles particularly susceptible to population declines, especially in response to small increases in adult mortality (Brooks and others 1990;others 1993, 1994;Gibbs and Shriver 2002;Bulté and others 2010).…”