Population dynamics of the Giant African River prawn Macrobrachium vollenhovenii Herklots 1857 (Crustacea, Palaemonidae) in the Cross River Estuary, Nigeria
Growth, mortality, recruitment, yield-per-recruit and present rate of exploitation of the African river prawn Macrobrachium vollenhovenii were studied in the Cross River Estuary, Nigeria. The research was based on length-frequency data collected between January 1997 and June 1998, and FAO-ICLARM Software (FiSAT) routine runs. Growth parameters obtained from the seasonalized von Bertalanffy growth function were L‡ 213.63 and 198.99 mm, K = 1.24/year and 1.24/year; C = 0.95 and 0.95; WP = 0.6 and 0.45, for M. vollenovenii males and females, respectively. Using the seasonalized length-converted catch curves, the instantaneous rate of total mortality Z was estimated as 3.93/year and 6.85/year for males and females. Natural mortality M, fishing mortality F, and exploitation rate E of both sexes were 2.21/year and 2.27/year, 1.72/year and 4.58/year, and 0.44 and 0.67, respectively. The length at first capture Lc estimated from the probability of capture routine was 44.25 mm and 73.41 mm for males and females. One recruitment peak was observed for males, and two of unequal strength for females. Length-weight relationship gave ebf values of 3.483 and 3.329 for males and females, respectively. The relative yield-per-recruit analysis predicted maximum exploitation rates (Emax) of 0.42 and 0.47 as against current exploitation rates of 0.44 and 0.67 for males and females and suggest that only female M. vollenhovenii are being over-exploited. Hence, it is proposed that fishing on females during the reproductive season is reduced, and that the return of egg-bearing females into the waters is enforced.
Nwosu F. and Wolff M. (2006) Population dynamics of the Giant African River prawn Macrobrachium vollenhovenii Herklots 1857 (Crustacea, Palaemonidae) in the Cross River Estuary, Nigeria. West African Journal of Applied Ecology 9(1). 10.4314/wajae.v9i1.45681
@article{Nwosu2006,
Title = {Population dynamics of the Giant African River prawn Macrobrachium vollenhovenii Herklots 1857 (Crustacea, Palaemonidae) in the Cross River Estuary, Nigeria},
Author = {Nwosu, FM and Wolff, Matthias},
Editor = {},
Journal = {West African Journal of Applied Ecology},
Year = {2006},
Volume = {9},
Doi = {10.4314/wajae.v9i1.45681},
Abstract = {Growth, mortality, recruitment, yield-per-recruit and present rate of exploitation of the African river prawn Macrobrachium vollenhovenii were studied in the Cross River Estuary, Nigeria. The research was based on length-frequency data collected between January 1997 and June 1998, and FAO-ICLARM Software (FiSAT) routine runs. Growth parameters obtained from the seasonalized von Bertalanffy growth function were L‡ 213.63 and 198.99 mm, K = 1.24/year and 1.24/year; C = 0.95 and 0.95; WP = 0.6 and 0.45, for M. vollenovenii males and females, respectively. Using the seasonalized length-converted catch curves, the instantaneous rate of total mortality Z was estimated as 3.93/year and 6.85/year for males and females. Natural mortality M, fishing mortality F, and exploitation rate E of both sexes were 2.21/year and 2.27/year, 1.72/year and 4.58/year, and 0.44 and 0.67, respectively. The length at first capture Lc estimated from the probability of capture routine was 44.25 mm and 73.41 mm for males and females. One recruitment peak was observed for males, and two of unequal strength for females. Length-weight relationship gave ebf values of 3.483 and 3.329 for males and females, respectively. The relative yield-per-recruit analysis predicted maximum exploitation rates (Emax) of 0.42 and 0.47 as against current exploitation rates of 0.44 and 0.67 for males and females and suggest that only female M. vollenhovenii are being over-exploited. Hence, it is proposed that fishing on females during the reproductive season is reduced, and that the return of egg-bearing females into the waters is enforced.},
}
TY - JOUR
AU - Nwosu, FM
AU - Wolff, Matthias
TI - Population dynamics of the Giant African River prawn Macrobrachium vollenhovenii Herklots 1857 (Crustacea, Palaemonidae) in the Cross River Estuary, Nigeria
T2 - West African Journal of Applied Ecology
PY - 2006
VL - 9
DO - 10.4314/wajae.v9i1.45681
AB - Growth, mortality, recruitment, yield-per-recruit and present rate of exploitation of the African river prawn Macrobrachium vollenhovenii were studied in the Cross River Estuary, Nigeria. The research was based on length-frequency data collected between January 1997 and June 1998, and FAO-ICLARM Software (FiSAT) routine runs. Growth parameters obtained from the seasonalized von Bertalanffy growth function were L‡ 213.63 and 198.99 mm, K = 1.24/year and 1.24/year; C = 0.95 and 0.95; WP = 0.6 and 0.45, for M. vollenovenii males and females, respectively. Using the seasonalized length-converted catch curves, the instantaneous rate of total mortality Z was estimated as 3.93/year and 6.85/year for males and females. Natural mortality M, fishing mortality F, and exploitation rate E of both sexes were 2.21/year and 2.27/year, 1.72/year and 4.58/year, and 0.44 and 0.67, respectively. The length at first capture Lc estimated from the probability of capture routine was 44.25 mm and 73.41 mm for males and females. One recruitment peak was observed for males, and two of unequal strength for females. Length-weight relationship gave ebf values of 3.483 and 3.329 for males and females, respectively. The relative yield-per-recruit analysis predicted maximum exploitation rates (Emax) of 0.42 and 0.47 as against current exploitation rates of 0.44 and 0.67 for males and females and suggest that only female M. vollenhovenii are being over-exploited. Hence, it is proposed that fishing on females during the reproductive season is reduced, and that the return of egg-bearing females into the waters is enforced.
ER -
