Effects of Chase Boat Use, Electrofishing Duration, and Water Velocity on Sample Efficiency and Size Structure of Blue Catfish

Abstract

Chase boats are used to assist in the capture of Blue Catfish Ictalurus furcatus because they often surface relatively far from the electrofishing boat (electrofisher) when incapacitated by low‐frequency, pulsed DC. We conducted this study to determine how chase boat use affects size‐related and capture efficiency metrics of Blue Catfish, and we concurrently examined possible confounding effects of sample duration and velocity on these metrics. We used DC at 15 pulses/s in 5‐ or 10‐min runs during four trials that were stratified by reservoir zone, season, and macrohabitat over a 2‐year period in Pool 10 of the Arkansas River (Lake Dardanelle, Arkansas). We captured 4,330 fish in 96 samples and analyzed the catch data by size‐group (all fish; >199, >299, and >509 mm). We compared samples of fish captured by an electrofisher alone with those collected by the electrofisher in combination with a chase boat (chase+). The electrofisher‐only protocol captured a greater proportion of fish less than 300 mm compared to the chase+ protocol, but length‐frequency distributions of larger‐size fish did not differ. Overall catch was greater for the chase+ protocol, with the difference generally increasing by size‐group except for the largest fish. Catch efficiency was greater for 5‐ versus 10‐min samples for both protocols, with the relative difference increasing as fish size increased. Calculated values of the proportional size distribution of quality‐size fish were sufficiently similar among all combinations of protocol and duration for management purposes. The practical implication is that an electrofisher‐only protocol can be used to collect representative samples of Blue Catfish, but the use of a chase boat increases the average catch per boat.

Evaluating Single‐ Versus Chase‐Boat Low‐Frequency Electrofishing for Assessing Flathead Catfish and Blue Catfish Populations in a Large River

“…Sampling catfishes with a single low‐frequency electrofishing boat may appeal to researchers because it is cheaper, logistically easier, and allows for more sites to be sampled (Cunningham 2004; Daugherty and Sutton 2005; Moran and Stoeckel 2021). In this study, the chase‐boat configuration provided greater CPUE of Flathead Catfish and Blue Catfish than did the single‐boat configuration and, in general, fewer sites were needed to meet precision and catch objectives with the chase‐boat configuration.…”

“…Consequently, sampling protocols often specify the use of one or more chase boats to aid in netting fish (Bodine and Shoup 2010). In reservoirs, chase boats increase catches of Blue Catfish compared with using only the electrofishing boat to collect fish (Moran and Stoeckel 2021) but may not increase catches of Flathead Catfish (Cunningham 2004). In rivers, using a chase boat may increase Flathead Catfish catch under some flow conditions (Daugherty and Sutton 2005).…”

“…The addition of one or more chase boats may also influence the size distribution of the catfish that are collected using low‐frequency electrofishing; however, few studies have examined this issue and results have been mixed. For Blue Catfish, Moran and Stoeckel (2021) found that a single‐boat configuration resulted in the capture of a greater proportion of smaller individuals than did a chase‐boat configuration; however, for Flathead Catfish, Cunningham (2004) and Daugherty and Sutton (2005) found no significant difference in the size of fish captured between single‐ and chase‐boat protocols. Using chase boats necessitates more resources per sampling event than using only a single electrofishing boat and is therefore more costly (Schramm et al.…”

“…Using chase boats necessitates more resources per sampling event than using only a single electrofishing boat and is therefore more costly (Schramm et al. 2002) and logistically challenging (Moran and Stoeckel 2021). Efficient deployment of personnel sampling resources is important to maximize spatial sampling coverage, a particularly important consideration in expansive, large river systems.…”

Catfish 2020, A Clear Vision of the Future

“…For Blue Catfish, 5-min lowfrequency electrofishing (LFE) samples provide similar precision and population parameters as 10-min samples, resulting in greater efficiency when sampling in reservoirs (Shoup and Bodine 2021, this special issue), but this does not seem to be the case for river LFE sampling (Moran and Stoeckel 2021, this special issue). Blue Catfish LFE samples can be made even more efficient without the use of chase boats in rivers, but it may come at the cost of a size bias toward smaller fish (Moran and Stoeckel 2021). Blue, Channel, and Flathead catfish can be effectively sampled with bank poles (Dean et al 2021, this special issue), but more research is needed to determine the sampling effort required to produce adequate precision for population metrics obtained with this gear.…”