Accurate species description in the marine environment is critical for estimating biodiversity and identifying genetically distinct stocks. Analysis of molecular data can potentially improve species delimitations because they are easily generated and independent, and yield consistent results with high statistical power. We used classical phylogenetic (maximum likelihood and Bayesian inference) and coalescent-based methods (divergence dating with fossil calibrations and coalescent-based species delimitation) to resolve the phylogeny of the spiny lobster Panulirus homarus subspecies complex in the Indo-West Pacific. Analyses of mitochondrial data and combined nuclear and mitochondrial data recovered Panulirus homarus homarus and Panulirus homarus rubellus as separately evolving lineages, while the nuclear data trees were unresolved. Divergence dating analysis also identified Panulirus homarus homarus and Panulirus homarus rubellus as two distinct clades which diverged from a common ancestor during the Oligocene, approximately 26 million years ago. Species delimitation using coalescent-based methods corroborated these findings. A long pelagic larval life stage and the influence of ocean currents on post-larval settlement patterns suggest that a parapatric mode of speciation drives evolution in this subspecies complex. In combination, the results indicate that Panulirus homarus rubellus from the Southwest Indian Ocean is a separately evolving lineage and possibly a separate species.

Assessment of age, growth and stock parameters was carried out for the Indian mackerel Rastrelliger kanagurta (Cuvier) along the Muscat coast of Oman between October 2007 and September 2009. The length-weight relationship of the fish indicated the 'a' value as 0.0101 and 'b' value as 3.0589. The length based von Bertalanffy growth (VBG) parameters L ∞ K and t 0 estimated were 37.54 cm, 1.0 y -1 and -0.17 y respectively. The estimates of mortality rates showed the annual total mortality (Z) to be 2.98, the natural mortality (M) 1.62 and fishing mortality (F) 1.36. The MSY estimated by Cadima's estimator was 859 t and the predicted value by yield analysis stood at 1,273 t. The calculated exploitation rate (E) was 0.46. The Yw/R at F = 1.6 was 48 g. Estimates of higher MSY than the current yield, lower fishing mortality than natural mortality and lower E indicate scope for increase in yield of R. kanagurta from Muscat region.

The spiny lobster Panulirus homarus is widely distributed in the Indo-West Pacific. Along  the coast of Oman it supports an artisanal fishery using traps and tangle nets. The egg-bearing incidence of females  caught between 1989 and 2006 were analysed relative to month, lobster size and location of capture. The smallest female with external eggs had a carapace length (CL) of 54.6 mm, but only 9–18% of females of 60–69 mm CL carried eggs. This percentage increased significantly above 70 mm CL, and on average, 63% of individuals >90 mm carried eggs. Egg-bearing increased seasonally at the onset of the SW monsoon in May and June, when wind-driven upwelling reduces inshore water temperatures and increases primary productivity. The reproductive season extended over a 9-month period up to  January, with a pause in February to April. No geographical gradient in egg-bearing seasonality was  observed. The prolonged breeding season with multiple broods in large females conforms with the  typical pattern of   tropical palinurids. The 2-month open fishing season (15th October to 15th December) falls within the breeding season, and may be more optimally placed in February to April.

A data base including length frequency distributions and catches of the Scomberomorus commerson in Oman according to fleet (gear/technique) and region has been established to carry out length cohort analyses, determine yield per recruit and simulate changes in fishing effort and/or increase in minimum length limit in catches. The analyse of data showed that: (i) The average fishing mortality rate is moderate (0.5-0.6), but acts in part on the juvenile fraction of the stock. The exploitation pattern differs, however, among fleets with some fleet components targeting largely immature kingfish and others largely the adult stock. (ii) An increase in total fishing effort would lead to long-term losses in total catch; the losses would be highest for fleets that target the larger specimens. A reduction of the effort would, in the long term, lead to an increase in yield and spawning stock biomass. (iii) An increase of minimum length limit in catches would, in the long term, lead to a substantial increase in yield and spawning stock biomass; the gain in catch would be largest for fleet components that target the adult fraction of the stock and (iv) an increase in minimum length limit in catches combined with an increased selectivity of the fisheries (i.e. favorising fleets targeting the adult fraction of the stock) would lead to the highest gain in sustainable catch. In this case, the sustainable catch could be increased by more than 50%. Therefore, this option represents the optimal management strategy obtained in the present study.

Fringelip mullet (Crenimugil crenilabis) caught at Al Duqum and Salalah in the Arabian  Sea region of Omanwere sampled monthly between January 2001 and December 2002. The total length (TL) of mullet caught  with gill- and seine nets ranged from 12 to 54.5 cm (32.4 cm mean ± SD; n = 2445) but <2% of  specimens had a TL<24 cm, suggesting gear selectivity. Females dominated samples (1 : 0.36) and reached L at 32.8 cm TL (32.2 cm in males). Length weight relationships were non-linear and conversion factors between TL, fork length (FL) and standard  length (SL) were calculated. Proportionately, most females had ripe gonads in September and October, and males in September to November. Both female and male gonadosomatic indices (GSI) peaked in September and October and were lowest between May and August. The peak in reproductive activity coincides with the fall intermonsoon, when the Arabian Sea upwellings caused by the onshore winds of the SW monsoon season (June to August/September) retreat. During this intermonsoon period the inshore water temperatures begin to rise after reaching a minimum in August/September. Some reproductive activity also occurs in other months, particularly February, when water temperatures are seasonally lower.