Mugil liza is distributed along the western Atlantic coast. It is a commercially exploited species in Argentina, supporting a small-scale fishery conducted by an artisanal fleet. Age determination of fishes constitutes an important key issue for fishery management. The age, growth and recruitment of M. liza juveniles in Mar Chiquita coastal lagoon and Las Brusquitas creek (Buenos Aires, Argentina), were estimated by means of the analysis of the sagittal otoliths of fish collected during January to December of 2014. Ages were estimated by counting and measuring daily growth increments in otoliths under a light microscope. A total of 735 specimens ranging from 19 to 71.5 mm SL and from 67 to 212 days age was analysed. Lengths at previous ages were determined by back-calculation, a linear growth model was fitted to the back-calculated data: SL = 0.2468 + 2.0516; R2 = 0.9945. Two peaks of recruiters were observed from February to March, and from October to November in 2014. Mean ages in days of Querimana and juveniles at the recruitment time were 84.07 ± 14.43 days and 87.56 ± 19.51 days, respectively. The hatching dates of specimens showed two spawning seasons. One was from December 2013 to January 2014, and the second one from July to August 2014. The assessment carried on this work generated age determination values that support previous findings, contributing to make a more accurate description of the life-history model currently used. In addition, valuable information has been generated to give better advice for improving the management of the fishery resource.
Reproductive biology of the Brazilian menhaden, Brevoortia aurea (Clupeiformes), was studied in Mar Chiquita Coastal Lagoon. Its abundance was analysed in relation to environmental variables, and the main biological-reproductive parameters were estimated: size at first maturity, batch and relative fecundity, frequency distribution of oocyte diameters and gonadosomatic index (GSI). Moreover, its reproductive cycle was analysed histologically. Samples were collected from May 2012 to April 2013. Once the spawning period was detected, extra samples were added (October and November 2013). The specimens were caught with gillnets, at a distance of 2,300 meters from the mouth of the lagoon. The highest abundances were observed in the months of October and November. Both macroscopic and microscopic analysis allowed to confirm that in these months the saraca spawn in the mixo-eurihaline area of the lagoon. Females were recorded in the five phases of ovarian development. Histological and frequency distribution of oocyte diameters characterized this species as a batch spawner with undetermined fecundity. The fecundity varied between 19,900 and 178,508 oocytes/female. Relative fecundity ranged between 41 and 381 oocytes/g female ovary free. The size at first maturity was estimated on 277 and 265 mm total length for females and males, respectively.
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