An Assessment of the Spiny Lobster Panulirus homarus Fishery in Oman — Another Decline in the Western Indian Ocean?

Abstract

The scalloped spiny lobster Panulirus homarus supports numerous traditional diving,
trap and trammel net fisheries in the Western Indian Ocean. Commercial catches made in 2003
to 2005 in the Arabian Sea region of Oman (a coastline of ~1100 km, comprising Dhofar and
Al-Wusta) were sampled for length and sex composition, and female reproductive condition.
On average, lobsters caught in Dhofar were larger than in Al-Wusta, and length-based estimates
of growth parameters, size at maturity and natural mortality were consistent with fast-growing
tropical lobsters. Compared to historical data from Oman dating from the late-1980’s (with peak
catches of >2000 t/yr) and mid-1990’s, recent landings, average lobster size and size at maturity
were considerably lower. A length-based cohort analysis suggested that fishing mortality does not
impact on lobsters <60 mm carapace length, but that it has depleted those >80 mm. The spawning
biomass ratio (Bsp/B) of <25% is sensitive to increases in fishing mortality. Existing regulations
are not regularly enforced, and the situation in Oman appears to be typical of lobster fisheries
in the northwestern Indian Ocean, where few well-founded management plans exist and several
declines in catches have been reported.