Baseline data of the presence of meso and microplastics in digestive tract of a commercially important teleost fish from the Rio de la Plata Estuary System (Southwest Atlantic Ocean)

In this paper, we analyze the occurrence, abundance, and type of plastic debris (PD) present on the digestive tracts of 65 white croakers (Micropogonias furnieri) catches from Rio de la Plata Estuary System (RLPES). Eighty percent of individuals analyzed had ingested PD, of which 156 were thread-like plastics (FO = 83.9 %) and 30 were fragments (FO = 16.1%). The average number of pieces per digestive tract was 2.83 ± 3.14. Microplastic represented 85% of PD, the majority of these pieces were <2 mm, and the preeminent color was blue. The RLPES is the area of the Southwest Atlantic Ocean that concentrates most of the records of plastic debris on the environment, where the white croaker is the main commercial fish. In addition, M. furnieri constitutes a key prey of several predators in the area. Although preliminary, this is a relevant contribution to the knowledge of marine debris pollution and its impact on the Southwest Atlantic Ocean organisms, particularly at the RLPES.

Effects of six codend meshes on the size selection of juvenile white croaker (Pennahia argentata) in demersal trawl fishery of the South China Sea

White croaker (Pennahia argentata) is a commercially important but overexploited species that is often caught in trawl fishery of the South China Sea (SCS). The codend size selectivity for this species in the local commercial trawl fishery is of concern when considering the established minimum landing size (MLS). This study investigated the size selectivity of white croaker for six different diamond-mesh codends with mesh size from 25 to 54 mm. We paid special attention to two codends, made with meshes of 25 and 40 mm in size, which are currently used according to the regulations established in the SCS. The results demonstrated that the legal codends do not perform satisfactorily in the fishing grounds where juvenile white croaker is relatively abundant. This is because at a length similar to the minimum landing size of the species (MLS = 15.0 cm), all white croaker were retained, and the estimated discard ratio was >97% in both cases of legal codends. Our study showed that by increasing the mesh size, the size selection of tested codends could be improved for white croaker, and the retention rates for juvenile fish would decrease. However, none codend was proved efficient to release undersized white croaker suggesting that other gear design changes may be necessary.

Germ cell-less hybrid fish: ideal recipient for spermatogonial transplantation for the rapid production of donor-derived sperm†

An interspecific hybrid marine fish that developed a testis-like gonad without any germ cells, i.e., a germ cell-less gonad, was produced by hybridizing a female blue drum Nibea mitsukurii with a male white croaker Pennahia argentata. In this study, we evaluated the suitability of the germ cell-less fish as a recipient by transplanting donor testicular cells directly into the gonads through the urogenital papilla. The donor testicular cells were collected from hemizygous transgenic, green fluorescent protein (gfp) (+/−) blue drum, and transplanted into the germ cell-less gonads of the 6-month-old adult hybrid croakers. Fluorescent and histological observations showed the colonization, proliferation, and differentiation of transplanted spermatogonial cells in the gonads of hybrid croakers. The earliest production of spermatozoa in a hybrid recipient was observed at 7 weeks post-transplantation (pt), and 10% of the transplanted recipients produced donor-derived gfp-positive spermatozoa by 25 weeks pt. Sperm from the hybrid recipients were used to fertilize eggs from wild-type blue drums, and approximately 50% of the resulting offspring were gfp-positive, suggesting that all offspring originated from donor-derived sperm that were produced in the transplanted gfp (+/−) germ cells. To the best of our knowledge, this is the first report of successful spermatogonial transplantation using a germ cell-less adult fish as a recipient. This transplantation system has considerable advantages, such as the use of comparatively simple equipment and procedures, and rapid generation of donor-derived spermatogenesis and offspring, and presents numerous applications in commercial aquaculture.