Catchability and Diversity of Fish Species Captured by Gill Net in New Calabar River, Nigeria

Abstract

The aim of this study was to analyze fish species caught by gill nets and fish diversity of the New Calabar River. Three sampling stations were set based on the coverage situation of the river and ichthyofauna associated with gill nets were sampled twice monthly from February to July 2018. A total of 3,251 fish specimens, representing 11 orders, 15 families, and 28 species, were captured. The order Perciformes was identified as the most abundant representing five families while the remaining had one family each. The fish family Cichlidae was the most represented with seven species, and other notable families were Alestidae, Clupeidae, and Mugilidae, representing three species each. Prominent among the fish caught monthly included Liza falcipinnis, Mugil cephalus, Sarotherodon melanotheron, Sarotherodon galilaeus, Coptodon guineensis, and Sardinella maderensis. The mean catch per unit effort (CpUE) ranged from 3.15±0.2 to 4.85±0.2 kg unit-1 day11. Results of diversity indices revealed that Shannon-Wiener index values varied between 2.64 and 2.82, Simpson diversity ranged from 0.07 to 0.10, and Pielou’s evenness index values ranged from 0.85 to 0.95. The values obtained in this study showed that the status of fish diversity in New Calabar River was stable.

Fish species biodiversity of Dadin-Kowa reservoir: Current status

“…Cichlids and schilbeids were the dominant fish groups. The fish species composition of this study agreed with the findings of 31 who recorded 28 fish species in New Calabar. Twenty-seven ( 27) fish species were documented from Kalgwai river (Jigawa State, Nigeria) by 32 and Gilo river (Ethiopia) 33 .…”

“…The differences in fish species representation of Dadin-Kowa reservoir as compared to other study areas may be attributed to the differences in lake-basin morphometry, moderate exploitation, food sources, photo-period, reservoir size, riverine tributaries, seasonal migration 26,38 . While river abstraction, dynamics of hydrological regimes, fish species adaptation to lotic environment, geographical position, environmental, habitat quality, species number vary depending upon differences in sampling methods and sampling effort, as well as fish abundance 34,38,40,45 .…”

“…The susceptibility of a fish species to a fishing gear is likely linked with the habitat of fish species; unlike non-riverine system, riverine aquatic ecosystems are characterized with fluctuations of increasing species abundance, diversity and richness 45 . Habitats differences in species abundance can be as result of differences of sediments accumulation which serves as a precursor to food generation and liberation.…”