Please use this identifier to cite or link to this item: http://ir.library.ui.edu.ng:8080/jspui/handle/123456789/548
Title: LENGTH-BASED POPULATION DYNAMICS OF PRAWN (MACROBRACHIUM SPECIES) AS RESOURCE MANAGEMENT TOOL OF LAGOS LEKKI LAGOON SYSTEM
Other Titles: A THESIS IN THE DEPARTMENT OF WILDLIFE AND FISHERIES MANAGEMENT SUBMITTED TO THE FACULTY OF AGRICULTURE AND FORESTRY IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY, UNIVERSITY OF IBADAN
Authors: Abohweyere, P. O.
Keywords: Population dynamics
Macrobrachium vollenhovenii
Macrobrachium macrobrachion
Lagos - Lekki Lagoon System
Issue Date: Aug-2008
Abstract: Shrimp is the single most important foreign exchange earning fishery resource in the Nigerian waters accruing US$ 65 million in 2006. Macrobrachium vollenhovenii (Herklots, 1857) and Macrobrachium macrobrachion (Herklots, 1851) are important prawn species in the artisanal shrimp fisheries. However there is dearth of information on the population dynamics of the Macrobrachium species in the Lagos-Lekki Lagoon System. This study, therefore investigated the population dynamics of prawn. The study was carried out in five communities randomly selected among 28 communities with high fishing intensity around Lagos and Lekki Lagoons. Data were collected within 2 years (2002-2004) and accidental sample of respondents was interviewed and catches assessed. Monthly length frequency data of species total length grouped into l cm was analysed by FAO-ICLARM Stock Assessment Tools (FiSAT) software. The FiSAT determines estimates of the Von Berthalanffy Growth Formula (VBGF) parameters that form the baseline of other population parameters. Physico-chemical parameters were measured using Horiba U-I0 water checker. Relationship between environmental parameters and revenue generation were assessed. Technical Efficiency (TE) of the shrimp fishermen was determined using the stochastic catch function. Data were subjected to correlation analysis. Asymptotic length (L∞) and growth coefficient (K) for M. vollenhovenii were 18.8cm and 0.55 respectively, while growth performance index (ø’) was 2.50. For M. macrobrachion Loo) was 14.2cm while 0.85 and 2.30 were for K and 0' respectively. The slowest growth period for M. vollenhovenii and M. macrobrachion were recorded in September and July with Winter Point (WP) of 0.75 and 0.58 respectively. Recruitment pulse exhibited two peaks: M. vollenhovenii 6.60 and 2.80; M. macrobrachion 9.82 and 5.04. Total mortality (Z) was 2.67 year -1 for M. vollenhovenii, with an exploitation rate (E) of 0.49 while Z for M. macrobrachion was 3.33year -1 and E was 0.42. Exploitation of the resource is below optimum standard rate of 0.5. Length at first capture (L) was 3.12cm for M. vollenhovenii and 2.61cm for M. macrobrachion. Predicted relative yield per recruit (Y’/R) was 5.3 x 10-2 at 0.4 or Emax, and 5.0 x 10-2 at E0.5 for M. vollenhovenii while for M. macrobrachion the values were 5.6 x 10-2 at 0.4 or Emax, and 4.1 x 10-2 at E0.5 Virtual population analysis (VPA) gave length class 8.5cm as the highest in catch for M. vollenhovenii and 7.5cm for M. macrobrachion. Correlation between salinity and M. macrobrachion was r = 0.58, while for pH and M. vollenhovenii was r = -0.67 (P<0.05). Investment cost on craft per fisherman ranged from N6,000 to N108,498. The average monthly fisherman revenue was NI02,884.4 while mean TE was 0.64. The average fisherman age was 49 years. Population parameters obtained from length frequency data were vital in the management of prawn resource. Predicted relative yield and biomass per recruit revealed that best yield from prawn in the Lagos-Lekki Lagoon System was achieved before the E0.5 Hence, optimum management option for the resource sustainability is to ensure that the present exploitation rate is not exceeded.
URI: http://hdl.handle.net/123456789/548
Appears in Collections:Academic Publications in Wildlife and Fisheries Management

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