Aquaculture and Fisheries最新文献

Biofouling is a major issue in aquaculture cages and nano materials based antifouling strategies became more prominent in recent years. Polyethylene aquaculture cage net surface which is modified with polyaniline and nano-copper oxide (CuO), reported to have biofouling resistance. Leaching of nano CuO from the net to the aquatic environment and its bioaccumulation in fish is the major concern against the technology adoption. The present study aimed to understand the accumulation of copper in fishes grown in a nano CuO treated aquaculture cage net. Studied the leaching pattern of nano CuO, biofouling inhibition and changes in strength of the cage net due to the nano CuO treatments. Fishes grown in the treated cages exhibited normal growth characteristics with no signs of abnormalities and also copper in their organs were within the prescribed standard limit. The CuO treated cage net exhibited excellent biofouling resistance and the percentage of occlusion of mesh by foulers were 56.77% more efficient than untreated cage net. Rate of nano CuO leached to the aquatic system was less than 8 μg/g·d. The fouling organism assemblage on untreated and treated net was 18 and 11 species, respectively. Major calcareous shelled foulers were absent on treated nets. The study highlighted the potential application of nano CuO treatment to control biofouling in aquaculture cages.

Time series from fisheries often contain multiple missing data. This is a severe limitation that prevents using the data for research on population dynamics, stock assessment, forecasting, and, hence, decision-making around marine resources. Several methods have been proposed to impute missing data in univariate time series. Still, their performances depend not only on the amount of missing data but also on the data structure. This study compares the performance of twelve imputation methods on the time series of marine fishery landings for six species in the Colombian Pacific Ocean. Unlike other studies, we validate the precision of the imputations in the same target time series that include missing data, using the Known Sub-Sequence Algorithm (KSSA), a novelty validation approach that simulates missing data in known sub-sequences of the target time series. The results showed that the best methods for imputation are Seasonal Decomposition with Kalman filters and Structural Models with Kalman filters fitted by maximum likelihood. Results also show that validating the imputation methods with other time series different to the target time series, leads to wrong imputation methods choices. It is noteworthy that these methods and also the validation framework are mainly suited to time series with non-random distribution of missing data, this is, missing data produced systematically in chunks or clusters with predictable frequency, which are common in marine sciences.

Among vertebrate species, fishes are considered to be the most developmentally diverse taxa exhibiting remarkable gonadal plasticity with capacity of sex reversal. Sex determination in teleost fishes is governed via a complex regulatory network involving multiple genetic, environmental (temperature, population density, pH), social interaction/stress factors. Piscine germ-line originates as Primordial germ cells (PGC) from cleavage blastomeres/endoderm and gets specified by maternal inheritance of Vasa, Nanos, Tdrds, Dnd, Dazl etc and subsequently migrates to reach the embryonic gonadal primordium. Post-hatching, mitotically active germ cells (Gc) continue to proliferate via two distinct pathways-firstly, stem cell-like mode followed by meiosis-committed cystic division. In Japanese rice fish medaka, Oryzias latipes sex gets determined on the chromosomal basis, where XY becomes a male because of testicular Dmy transcription and XX develops as female owing to Gc restricted Foxl₃ expression. Sex specific germ-line stem cell systems also have been found in adult O. latipes. Intriguingly in teleost fishes, the developmental fate of transplanted Gc do not depend on the sex of the donor rather solely relies upon the sex of the recipient. Furthermore, sexually mature piscine gonads remain developmentally plastic showing extensive responsiveness towards sex steroids. The critical regulation of gonadal differentiation is directed by female specific 17β-estradiol (E₂) and bio-active male androgen 11-keto-testosretone (11-kT). Various transcription factors (TFs) e.g.- Dmrt1, DAX1, Ad4BP/SF-1, Foxl₂ regulate the bio-conversion rate of testosterone (T) to either E₂ or 11-kT. Similarly, multiple endocrine factors (EFs) e.g.- LH, FSH, E₂, 11-kT and growth factors (GFs) e.g- AMH, GSDF, IGF-1/3, GDF-9/BMP-15 critically induce Gc differentiation to regulate the gametogenic output. In this article we have precisely discussed the endocrine regulation of Gc development during gonadal maturation of teleosts.

The effects of different dietary lipid levels on lipid accumulation, inflammatory response, serum bio-chemical index and histological features of intestine and hepatopancreas of O. macrolepis was experimentally evaluated in an eight-weeks study. Fish (initial weight 50.11 ± 2.86 g) were fed with five iso-nitrogenous diets (around 390 g/kg protein) varying with lipid level (5%, 7%, 9%, 11%, 13%, being LL5, LL7, LL9, LL11, and LL13 respectively) in triplicates. Results showed that the content of crude lipid in carcass and hepatopancreas were not affected by dietary lipid levels (P > 0.05). Serum ALT, TP, HDL-c and MDA, etc., were not significantly affected by diets (P > 0.05), while serum total antioxidant capacity in LL9 and LL11 groups were significantly higher than the other groups (P < 0.05). Histological features of hepatopancreas and intestine showed no significant difference among the five diets (P > 0.05), while the height of intestine villus showed the higher trend in LL9 compared with other groups. The relative expression of lipid metabolism related genes (ppar α, cpt-1α, fas, and hsl) and immune response related genes (tlr 22, nrf 2, tnfα, and il-γ) in the hepatopancreas of fish fed diets differing in their crude lipid levels were not significantly different (P > 0.05). The results suggested that a proper dietary lipid level of 9%–11% could maintain higher antioxidant and health status of adult O.macrolepis.