Comparing Channel Catfish Populations in the Fragmented Minnesota River

Abstract

AbstractChannel Catfish Ictalurus punctatus provide important fisheries in lotic systems throughout much of North America, but few studies have evaluated the influence of dams and habitat fragmentation on their populations. The Minnesota River is an important recreational catfish fishery in Minnesota that is fragmented by Granite Falls Dam, located 395 km upstream from the confluence with the Mississippi River. Granite Falls Dam is a significant barrier to upstream fish passage; consequently, the upstream fish community is less diverse than the downstream community and habitat availability differs between reaches. For this study, hoop‐net assessments conducted by the Minnesota Department of Natural Resources during 2014–2017 were used to compare Channel Catfish catch rates, size structure, growth, and annual survival between the upstream and downstream reaches. Hoop‐net catch rates upstream (mean ± SE = 45.1 ± 5.2 fish/net‐night) were significantly greater by an order of magnitude compared to catch rates downstream (3.9 ± 0.4 fish/net‐night). Size structure of Channel Catfish also significantly differed between reaches: the percentage of stock‐length (≥280‐mm) fish that were preferred length or larger (≥610 mm) was 28.4% downstream compared to 5.8% upstream. Annual survival estimates and growth indices were generally similar between reaches, but there was evidence of greater longevity downstream, where the oldest aged fish were 24 years compared to 19 years upstream. This study demonstrates population differences that may be influenced and exacerbated by habitat fragmentation and provides support for considering each population individually when making future management decisions.