Coping with steep exploitation rates in an open access fishery

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Fisheries in many developing nations commonly operate in an open access regime, largely due to fundamental factors like poor fisheries institutions and the need to maximize food security and employment. Such factors are evident in Hormozgan, the largest fishing province in Iran, rendering many fish stocks in precarious conditions. The catch of the Indian halibut in Hormozgan has increased sixfold over the past 17 years, along with increasing socioeconomic importance. Yet ever-growing exploitation rates and lack of regulations are threatening both the sustainability of the stock and the livelihoods of fishers that depend on it. In this paper, we examine the status of the Indian halibut using an age-structured model and demonstrate the effectiveness of managing the age selectivity (age at 50% vulnerability to capture (av)) on future biomass and yields under excessive exploitation rates. Our results indicated that the annual exploitation rates had been steadily climbing since 2001, with the stock currently experiences overfishing. Future projections showed that, under intensified exploitation rates (e.g., 0.7 year−1), increasing av from the present 4 years (mean size 39.7 cm) to 5 years (43.3 cm) is expected to maintain biomass at a sustainable level (61% of an unfished level) and enhance yields by 84%. Higher av policies (6 and 7 years) would result in less depletion but forgo substantial yields. This study underscores the potential of size restrictions in sustaining open access fishery resources subjected to steep exploitation rates.