ESTIMATING OF SOME BIOLOGICAL PARAMETERS AND YIELD PER RECRUIT FOR FISHERY MANAGEMENT OF GREY MULLET, Mugil cephalus IN BARDWILL LAGOON
Attia El_Aiatt1 and Mohamed Salem2
1 National Institute of Oceanography and Fisheries NIOF.
2 Faculty of Environmental
Agriculture Sciences, El-Arish – University.
|Received 1/ 8/ 2017||
Accepted 5/ 9/ 2017
Biological parameters provide fundamental information for re-stocking in fisheries. Growth, mortality and yield per recruit of Grey mullet (Mugil cephalus) were studied in Bardawill lagoon. A total of 961 specimens (12.8 to 49.8 cm total Length and 28 to 1222 gm total weight), were collected from April to December, 2015. Age was determined by scales where age groups 0 to 6 years. Growths in length and weight at the end of each year were calculated as 21, 28.5, 33.8, 37.4, 40.7 and 43.9 cm for the 1, II, III, IV, V and VI year of life respectively. The relationship between length and weight was W= 0.0108*L 2.963.The growth parameters of von Bertalanffy equation were calculated as (L∞= 52.19 cm, K = 0.261 year-1 and t0 = -0.9698 year). Growth performance index (φ′ = 2.85). Mortality rates were 0.7425 yr−1, 0.3681 yr−1and 0.3744yr−1 for total, natural and fishing mortality respectively. The currently exploitation rate E = 0.504. The length at first capture (Lc) was 27.5 (1.898 year). The results of age at first capture and the current exploitation rate indicated that the small fish were caught at higher fishing effort level. The current mesh size should be increased in order to increase the tc to 2.5 year which achieves the highest yield at current fishing effort. Thus, the current effort of M. cephalus should be stabilized at increase of tc to 2.5 year and if possible should be reduced. So, fishers must searching for a way to catch fish bigger than 31 cm with no increase in fishing effort but must reduce of fishing effort. Also, adjustment work in the mesh size of fishing nets to catch fish larger than 31 cm (fish at mature stage).
Keywords: Bardawil lagoon, Mugil cephalus, age, growth, mortality, per-recruit analysis, stock enhancement.