Catch per unit effort, maximum sustainable yield and exploitation of demersal fish of Omani artisanal fishery

Abstract

The artisanal fishery in Oman contributes over 90% of the total marine catch. The fish stocks in this fishery suffer from an increase of exploitation pressure due to open access system[1,2]. In that fishery, small fiberglass boats powered with engine dominate the fleets constituting about 99%[2]. The boats are less than 12 m length fishing with gears such as traps, bottom gill nets and hand lines. These boats obviously increased in the fishery during the last decade[3]. This is expected to have direct effect on the fish stocks and exploitation status. The production of artisanal fishery composed of some different categories of fish groups classified as large pelagic fish, small pelagic fish, demersal fish, sharks and rays, mollusks and crustaceans. Demersal fish category includes some important fish species which are selected for the present study. These fish include emperors (Lethrinus lentjan and Lethrinus nebulosus, family Lethrinidae), groupers (Epinephelus areolatus, Epinephelus chlorostigma and Epinephelus tauvina, family Serranidae), sea breams [Acanthopagrus bifasciatus (A. bifasciatus) and Argyrops filamentosus (A. filamentosus), family Sparidae], rabbit fish (Siganus canaliculatus, Siganus rivulatus, Siganus spinus and Siganus javus, family Siganidae), croakers [Atractoscion aequidens (A. aequidens), family Sciaenidae], sweet lips (Plectorhinchus pictus and Plectorhinchus schotaf, family Haemulidae), snappers (Lutjanus ehrenbergii and Lutjanus malabaricus, family Lutjanidae), jobfish [Pristipomoides typus (P. typus), family Lutjanidae], ribbonfish [Chirocentrus dorab (C. dorab) and Trichiurus lepturus (T. lepturus), family Trichuridae] and catfish [Arius polystaphylodon (A. polystaphylodon), family Ariidae]. Because of their importance, the exploitation of these species should be well managed. Generally to manage human exploitation of resources, it is necessary to know how much can be safely taken without depleting them, and without otherwise negatively impacting the environment. In case of fishing when discussing the limits of exploitation of the fish stocks, the concept of maximum sustainable yield (MSY) should be considered as a key tool for fisheries management. MSY for a given fish stock means the highest possible annual catch that can be sustained over time, by keeping the stock at the level producing maximum growth[4]. The MSY refers to a hypothetical equilibrium state between the exploited population and the fishing activity. MSY as a tool for stock evaluation being easily adopted when data on fishing effort and catch are available from which catch per unit effort (CPUE) could be analysed over a range of fishing season[4]. In Oman, data on catches in weights and number of fishing boats (fishing effort) are available in statistical fishery book issued annually by ministry of agriculture and Fishery Wealth. MSY and surplus production models were discussed and adopted in fishery management in many previous studies[5-20]. One objective of the present study is to investigate the effect of the increase of fishing boats in artisanal fishery on the catch of demesral fishes per boat. Another objective is to estimate the MSY of these fishes. Then it is possible to have an evaluation of their exploitation status. ARTICLE INFO ABSTRACT