Sexual Maturity, Spawning Periodicity and Fecundity of Obtuse Barracuda Sphyraena obtusata (Cuvier, 1829) along Karnataka Coast, Southeastern Arabian Sea

Background: The success or failure of spawning in any population affects the fishery. Hence, studies on spawning, maturation, fecundity and length at first maturity become essential in drafting management strategies. The detailed information on reproductive traits of Sphyraena obtusata will be helpful in sustainable management and conservation in the study area. Methods: Three hundred and fifty five specimens of S. obtusata were collected fortnightly from Mangaluru and Malpe fishing harbors during August 2019 to March 2020. Maturity of gonads was examined by macroscopic and histological investigations. Spawning periodicity was worked out based on maturity stages and seasonal gonadosomatic index. Gravimetric method of analysis was employed to evaluate the fecundity from randomly collected samples of gravid females. Result: Overall sex ratio revealed that the population had significantly higher (p less than 0.05, X2 test) proportion of females than males. The length at 50% maturity (Lm50) for females and males was estimated at 21.1 and 21.5 cm respectively. The gonadosomatic index (GSI) and the availability of matured individuals for both the sexes in various percentage indicated a prolonged breeding period from October to March with peaks in November and December. The absolute fecundity varied from 91,942 eggs (20.0 cm TL) to 1,34,445 eggs (27.0 cm TL) with an average of 1,12,878 ± 2,984 hydrated oocytes per female.

Physical-biological interactions underlying the phylogeographic patterns of coral-dependent fishes around the Arabian Peninsula

ABSTRACTAimTo test the hypothesis that phylogeographic pattern of coral-dependent fish species inhabiting the Arabian Peninsula may be driven by a combination of ocean circulation, larval behavior and seascape features.LocationThe present study focuses on three such putative oceanographic barriers around the Arabian Peninsula: the Bab el-Mandeb Strait, the Strait of Hormuz and the upwelling off Oman.TaxMultitaxa.MethodsA biophysical modeling system that relies on stochastic Lagrangian framework and Individual-Based Model was used to simulate larval dispersal through the three putative barriers, by tracking three-dimensional movements of virtual particles in ocean circulation scenarios. We explored the range of dispersal capabilities across reef fish species by creating 72 hypothetical strategies, each representing a unique combination of five biological traits: pelagic larval duration, spawning periodicity, mortality rate, reproductive output and vertical migration.ResultOur results showed that the strength of the barriers was highly variable as a function of all biological traits (except reproductive output) and indicated high asymmetry of connectivity, and hence gene flow, between adjacent areas. In addition, direction and distance travelled by the virtual larvae varied according to both the geographic position of releasing site and biannual monsoonal winds. On average, larvae released during the summer exhibited a higher potential for dispersal than larvae released in wintertime.Main conclusionsOur biophysical models complement the few existing empirical research on population genetics, and the predictions presented here serve as testable hypotheses for future phylogeographic studies around the Arabian Peninsula.

Reproductive biology of the orangefin ponyfish Photopectoralis bindus (Valenciennes, 1835) off Mangaluru coast, Karnataka

The spawning periodicity of Photopectoralis bindus (Valenciennes, 1835) was studied off Mangaluru coast from September 2015 to April 2016 using 490 specimens with total length 6.8-12.3 cm (9.6±0.9 cm) and body weight 4.6 -30.28 g (14.20±3.59 g). Results indicated that the average sizes at maturity were 9.3 cm (males) and 9.5 cm (females). The male-female ratio was 1:0.72. Absolute fecundity estimated was 9349±853 eggs that increased with fish size (R2 = 0.92). Higher gonado-somatic index (GSI) was observed in post-monsoon season with peak value in December (female: 3.39±1.00%; male: 2.84±0.796%) indicating seasonal spawning of the fish.

Age, growth, reproductive biology and spawning periodicity of the forktail rabbitfish (Siganus argenteus) from the Mariana Islands

In the present study, life-history traits of importance to fisheries management were estimated for the forktail rabbitfish (Siganus argenteus) based on fishery-dependent samples collected over a 2-year period in the Commonwealth of the Northern Mariana Islands. Age-based and reproductive information was derived from analysis of sagittal otoliths and gonads. The species is short-lived, with a maximum age of 7+ years, and females reach sexual maturity at ~1.3 years (21.8-cm fork length). Age distributions and total mortality rates were similar between sexes. However, females on average reached larger asymptotic sizes, with estimates of mean asymptotic length exceeding that of males by 2cm. Reproductive cycles, based on temporal variation in gonadosomatic index values and proportional frequency of active ovaries, demonstrated two annual activity peaks, consistent across 2years of sampling. Peak spawning occurred from March to May–June, whereas a second, smaller peak spanned August and September. In the Mariana Islands, S. argenteus represents a short-lived species with potential for rapid population turnover; 85% of the population is under 3years of age, whereas approximately half of all harvested individuals have reached reproductive maturity. Derived estimates of natural and fishing mortality indicate minimal concerns for the long-term fishery sustainability of this species under present levels of exploitation.