Scientific Research and Essays

  • Abbreviation: Sci. Res. Essays
  • Language: English
  • ISSN: 1992-2248
  • DOI: 10.5897/SRE
  • Start Year: 2006
  • Published Articles: 2768

Full Length Research Paper

Gillnet selectivity, seasonal, tidal and photoperiod variation in catch in the lower Nun River, Niger Delta, Nigeria

Martin E. Allison
  • Martin E. Allison
  • Department of Fisheries and Livestock Production, Niger Delta University, Wilberforce Island P. M. B. 017 Yenagoa, Bayelsa State, Nigeria.
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Daniel Okadi
  • Daniel Okadi
  • Department of Fisheries and Aquatic Environment, Rivers State University of Science and Technology, Port Harcourt, Rivers State, Nigeria.
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  •  Accepted: 21 December 2012
  •  Published: 31 January 2013


The fish species of the lower Nun River was sampled to determine gillnet selectivity and the effect of season, tide and photoperiod variation on the catch. A total of 11,156 specimens were caught belonging to 14 families consisting of 25 species. Gillnet selectivity was observed with a declining trend from the largest mesh size net of 15 mm (58%) in number and 59% by weight, 12 mm (33%) in number and 33% by weight with the least catch of about 9% by number and 8% by weight from the smallest (8 mm) net. In terms of seasonal variation, the rainy season catches were significantly higher (P< 0.05) than the dry season with relative abundance of 67 and 32% respectively. Tidal variation in the catches showed that catches were higher during the low tidal period (61%) than the high tide (39%). Significant photoperiod differences (P < 0.05) were observed with higher catches by day (58%) than by night.


Key words: Gillnet selectivity, seasonal, tidal, photoperiod, variation, Nun River.