Differential Catch by Hoop Nets of Three Mesh Sizes in the Lower Platte River

Abstract

We sampled fish from six sites along the lower Platte River with cheese-baited hoop nets with mesh sizes of 25, 32, and 38 mm during 1989. Bank habitats sampled were categorized as naturally stabilized banks, eroding banks, revetments, and hard points. Nets were set approximately in proportion to availability of bank habitats at each site, We collected 1,023 fish in 976 net-nights. The 25-mm-mesh nets caught 82% of the fish in 45.5% of the total net-nights. Significantly fewer fish (18.0% of total) were caught in 32- and 38-mm-mesh nets from 54.5% of the net-nights. Hoop nets were species-selective–92.7% of the fish collected were channel catfish Ictalurus punctatus. Mean length of channel catfish significantly increased with mesh size: 266 mm (SD, 45.1 mm) with 25-mm-mesh nets, 320 mm (SD, 65.0 mm) with 32-mm-mesh nets, and 316 mm (SD, 130.4 mm) with 38-mm-mesh nets. The pattern of decreased capture with increasing mesh size was consistent within individual habitat types. General linear models based on rank-transformed channel catfish lengths indicated that all three mesh sizes were significantly different in terms of the mean locations of the ranked lengths. Care should be taken to standardize mesh size of hoop nets because of the differential capture among mesh sizes.