Thesis Abstract and Dissertation Abstracts
Fisheries of Euthynnus affinis and Scomberomorus commerson in Relation to Oceanographic and Atmospheric Parameters off the Coastal Waters of Dar es Salaam, Tanzania
Abstract Category: Science
Course / Degree: M. Sc (Marine Biology)
Institution / University: University of Dar es Salaam, Tanzania
Published in: 2010
Kawakawa, Euthynnus affinis and Kingfish, Scomberomorus commerson are one of the keystone large pelagic fish for their important roles played in marine ecosystems, fisheries and income generation to the local communities along Tanzanian coastline. In recent years, there has been a significant decline in the catch and biomass of landed E. affinis and S. commerson along the coastal waters of Tanzania. However their relationships with oceanographic and atmospheric parameters was poorly understood. Therefore, the present study was conducted to assess how fisheries of E. affinis and S. commerson relate to the seasonal variations in oceanographic and atmospheric parameters off the coastal waters of Dar es Salaam, Tanzania.
Fisheries data of the two species of fish, oceanographic and atmospheric parameters were collected between April to September 2008 and November 2008 to February 2009 during southeast monsoon (SEM) and northeast monsoon (NEM) seasons, respectively. A total of 2,591 E. affinis and 722 S. commerson were collected in both NEM and SEM seasons. Significantly higher seasonal variations in the catch per unit effort (CPUE) were observed for fishing trips undertaken during the day (p = 0.042) and at night (p = 0.045) for E. affinis and S. commerson (p = 0.004), respectively. Both oceanographic (seas surface temperature and salinity) and atmospheric (temperature, rainfall, solar radiation and wind speed) parameters showed a significant correlation to CPUE of E. affinis (r = range from - 0.58 to 0.98). For S. commerson, only the oceanographic parameters correlated significantly to CPUE (r = range from - 0.58 to – 0.79). The relationship between length-weight (exponent b) for samples of different sexes and seasons showed an isometric growth for both E. affinis and S. commerson. Gonad-somatic index revealed a year round spawning for both species. Mean stable isotopes signatures of 13C and 15N values showed that the two species feed on marine fish at different trophic position and they varied significantly (p< 0.05) with season whereas the most negative values and a wide range of trophic level were observed in NEM for E. affinis and in SEM for S. commerson.
In conclusion, the present findings showed the influence of oceanographic and atmospheric parameters on the CPUE of E. affinis and S. commerson implying that they have impacts on the population dynamics and biological indices of these species. Therefore, long term monitoring of the impacts regarding oceanographic and atmospheric parameters on the population dynamics and biological indices of E. affinis and S. commerson is recommended.
Thesis Keywords/Search Tags:
Euthynnus affinis, Scomberomorus commerson, Dar es Salaam, Catch per unit effort, Oceanographic and Atmospheric Parameters, Length weight relationship, Stable isotopes of 13C and 15N
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Submission Details: Thesis Abstract submitted by Johnson Mshana Grayson from Tanzania on 28-Jan-2011 11:11.
Abstract has been viewed 3016 times (since 7 Mar 2010).
Johnson Mshana Grayson Contact Details: Email: mshanajohn1@yahoo.com Phone: +255 684 884 569
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