Induction of meiotic gynogenesis in bagrid catfish (Pseudobagrus ussuriensis) with homologous sperm and its confirmation for female homogamety

The bagrid catfish, Pseudobagrus ussuriensis, exhibits significant sexual dimorphism in growth rate and body size with males growing faster than females. Therefore, an all‐male culture can dramatically increase the output and profitability of fishery products. According to the monosex breeding route, super‐male individuals’ acquirement by XY male sex reversal and artificial gynogenesis is the key step. An effective protocol to induce meiotic gynogenesis using homologous sperms has been developed in this study. The most effective UV irradiation for sperm genetic inactivation was found to be at a distance of 20 cm with 66 μW/cm² light intensity for 25 min. Optimal treatment for cold shock was 5 min post‐fertilization at 0‐4°C for 30 min, which gave the best survival rate of 13.65 ± 2.87%. The sex ratio in the meiotic gynogens showed a significant female‐biased deviation (p < .05); thirty meiogynogens and their parents were further analysed using a male‐specific AFLP marker, of which only the male parent produced a male‐specific DNA band of 412 bp. These results indicated the female homogametic XX/XY sex determination system in P. ussuriensis. The optimization of a protocol for the successful induction of meiogynogenesis in the bagrid catfish lays the basis for all‐male production and is useful in ascertaining the genetic sex determination system in this promising aquaculture species.     

Immunostimulatory effects of dietary poly‐β‐hydroxybutyrate in European sea bass postlarvae

The stable production of high‐quality fry in marine aquaculture is still hampered by unpredictable mortality caused by infectious diseases during larval rearing. Consequently, the development of new biocontrol agents is crucial for a viable aquaculture industry. The bacterial energy storage compound poly‐β‐hydroxybutyrate (PHB) has been shown to exhibit beneficial properties on aquatic organisms such as enhanced survival, growth, disease resistance and a controlling effect on the gastrointestinal microbiota. However, the effect of PHB on the developing immune system of fish larvae has so far not been investigated. In this study, the effect of feeding PHB‐enriched Artemia nauplii on survival, growth and immune response in European sea bass (Dicentrarchus labrax) postlarvae was examined. Amorphous PHB was administered to 28‐day‐old sea bass postlarvae over a period of 10 days. The survival and growth performance were monitored, and the expression of 29 genes involved in immunity, growth, metabolism and stress‐response was measured. While the expression of the insulin‐like growth factor 1 (igf1), an indicator of relative growth, was upregulated in response to feeding PHB, the larval survival and growth performance remained unaffected. After 10 days of PHB treatment, the expression of the antimicrobial peptides dicentracin (dic) and hepcidin (hep) as well as mhc class IIa and mhc class IIb was elevated in the PHB fed postlarvae. This indicates that PHB is capable of stimulating the immune system of fish early life stages, which may be the cause of the increased resistance to diseases and robustness observed in previous studies.     

Influence of nanochitosan/zeolite composite on growth performance,digestive enzymes and serum biochemical parameters in rainbow trout (Oncorhynchus mykiss)

Protective effects of nanochitosan/zeolite composite besides zeolite and chitosan/zeolite composite on rainbow trout growth, digestive enzyme activities and biochemical parameters were studied. Nanochitosan/zeolite hybrid composites with three different ratio of nanochitosan:zeolite (35:100, 3.5:100 and 0.35:100) were synthesized and analysed by X‐ray powder diffraction (XRD), thermal gravim (TG) analysis and scanning electron microscope (SEM) methods. Prepared composites as well as zeolite and control diets were fed to rainbow trout (50 g) for a period of 60 days. The addition of treated diets significantly improved growth performance compared to the control diet. Supplemental zeolite could only enhance the amylase activity in fish intestine, whereas other treatment groups could increase the pepsin activity besides intestinal alkaline phosphatase, trypsin and amylase activities. No differences were observed for intestinal acid phosphatase and lipase activities among the experimental diets. Meanwhile, serum total antioxidant activity and lipid peroxidation product, indicated by malondialdehyde (MDA), significantly increased and decreased, respectively, with some doses of administration, indicating the elevated antioxidant status in treatment groups. Serum‐specific marker enzymes, namely aspartate aminotransferase (AST) and alkaline phosphatase (ALP), were not affected in all groups. Meanwhile serum total protein in most treatment groups was significantly higher than the control group. Results showed that synthesized composites especially nanochitosan/zeolite composite at 5 g/kg had potential to enhance growth performance, digestive enzyme activities and some biochemical parameters in rainbow trout.     

Histological alterations in gills of shrimp Litopenaeus vannamei in low‐salinity waters under different stocking densities: Potential relationship with nitrogen compounds

Two experimental modules with different stocking densities (M1 = 70 and M2 = 120 shrimp /m²) were examined weekly over a culture cycle in tanks with low‐salinity water (1.9 g/L) and zero water exchange. Results showed survival rates of 87.7 and 11.9% in M1 and M2, respectively. Water temperature, pH, dissolved oxygen, electrical conductivity and chlorophyll a were not significantly (p > .05) different between modules. In contrast, the concentrations of nitrogen compounds were significantly (p < .05) different between modules, except nitrite‐N (M2 were 2.31 ± 1.38 mg/L N‐TAN, 0.18 ± 0.49 mg/L N‐NO₂^? and 6.83 ± 6.52 mg/L N‐NO₃^?; in M1: 0.97 ± 0.73 mg/L N‐TAN, 0.05 ± 0.21 mg/L N‐NO₂^? and 0.63 ± 0.70 mg/L N‐NO₃^?). When waters of both modules reached higher levels of ammonia and nitrite, histological alterations were observed in gills. The histological alterations index (HAI) was higher in M2 (5‐112) than in M1 (2‐22).     

Ecoviability for ecosystem‐based fisheries management

Reconciling food security, economic development and biodiversity conservation is a key challenge, especially in the face of the demographic transition characterizing many countries in the world. Fisheries and marine ecosystems constitute a difficult application of this bio‐economic challenge. Many experts and scientists advocate an ecosystem approach to manage marine socio‐ecosystems for their sustainability and resilience. However, the ways by which to operationalize ecosystem‐based fisheries management (EBFM) remain poorly specified. We propose a specific methodological framework—viability modelling—to do so. We show how viability modelling can be applied using four contrasted case‐studies: two small‐scale fisheries in South America and Pacific and two larger‐scale fisheries in Europe and Australia. The four fisheries are analysed using the same modelling framework, structured around a set of common methods, indicators and scenarios. The calibrated models are dynamic, multispecies and multifleet and account for various sources of uncertainty. A multicriteria evaluation is used to assess the scenarios’ outcomes over a long time horizon with different constraints based on ecological, social and economic reference points. Results show to what extent the bio‐economic and ecosystem risks associated with the adoption of status quo strategies are relatively high and challenge the implementation of EBFM. In contrast, strategies called ecoviability or co‐viability strategies, that aim at satisfying the viability constraints, reduce significantly these ecological and economic risks and promote EBFM. The gains associated with those ecoviability strategies, however, decrease with the intensity of regulations imposed on these fisheries.     

Reproductive resilience: a paradigm shift in understanding spawner‐recruit systems in exploited marine fish

A close relationship between adult abundance and stock productivity may not exist for many marine fish stocks, resulting in concern that the management goal of maximum sustainable yield is either inefficient or risky. Although reproductive success is tightly coupled with adult abundance and fecundity in many terrestrial animals, in exploited marine fish where and when fish spawn and consequent dispersal dynamics may have a greater impact. Here, we propose an eco‐evolutionary perspective, reproductive resilience, to understand connectivity and productivity in marine fish. Reproductive resilience is the capacity of a population to maintain the reproductive success needed to result in long‐term population stability despite disturbances. A stock's reproductive resilience is driven by the underlying traits in its spawner‐recruit system, selected for over evolutionary timescales, and the ecological context within which it is operating. Spawner‐recruit systems are species specific, have both density‐dependent and fitness feedback loops and are made up of fixed, behavioural and ecologically variable traits. They operate over multiple temporal, spatial and biological scales, with trait diversity affecting reproductive resilience at both the population and individual (i.e. portfolio) scales. Models of spawner‐recruit systems fall within three categories: (i) two‐dimensional models (i.e. spawner and recruit); (ii) process‐based biophysical dispersal models which integrate physical and environmental processes into understanding recruitment; and (iii) complex spatially explicit integrated life cycle models. We review these models and their underlying assumptions about reproductive success vs. our emerging mechanistic understanding. We conclude with practical guidelines for integrating reproductive resilience into assessments of population connectivity and stock productivity.     

Phosphorus‐enriched soils of urban and suburban Nanjing and their effect on groundwater phosphorus

Neither the phosphorus (P)‐rich soils in urban areas nor their environmental implications have been adequately studied. This study investigated soils of typical urban function zones in Nanjing/China, like park, residential areas, school yards, campus as well as suburb vegetable land and garbage filling sites, and meantime ground water in situ. Typical soils were also experimentally leached for P leaching evaluation. All studied soils were enriched with P with enrichment ratios varying from 2 to 10 for total P and 5 to 22 for NaHCO₃‐extractable P, as compared with the original parent soils. The C : P ratios also indicated strong enrichment of P in urban soils. In urban areas the maximum P layer appeared as buried under different depth while in suburban soils as epipedon. The various morphology of P distribution suggested different soil formation patterns, which were related to the land use history. Groundwater P was significantly correlated with the maximum extractable P content of P in soil profiles and even better with the weighted average P content of the whole profile or P content of the soil layer at or close to groundwater table. Dissolved P in experimental leachate was comparable with that of groundwater but higher than environmentally acceptable level. Furthermore, there was a significant correlation between solution P and different extractable P forms of the studied soils. Simple P tests can provide an evaluation of the potential risk of urban soils in discharging P to water system.     

Prediction of Cooked Rice Texture Using an Extrusion Test in Combination with Partial Least Squares Regression and Artificial Neural Networks

Spectral stress strain analysis was used in combination with partial least squares (PLS) regression and artificial neural networks (ANN) to predict nine sensory texture attributes of cooked rice. The models calculated with ANN were significantly more accurate in predicting most of the sensory texture characteristics evaluated than the PLS models. Furthermore, ANN models were more robust and discriminative than PLS models.     

Relationships of Selected Physical,Chemical, and Sensory Parameters in Oat Grain,Rolled Oats,and Cooked Oatmeal—A Three‐Year Study with Eight Cultivars

Eight Scandinavian oat cultivars were studied as grains, groats before and after kiln drying, rolled oats, and oatmeal for 62 physical, chemical, and sensory parameters over three consecutive crop years. The objectives were to study cultivar and year differences, and the relationships between parameters to find out the cultivars most suitable for rolled oats production and to understand how grain parameters are reflected on groat, rolled oat, and oatmeal characteristics. The cultivars and crop years differed (P < 0.05) in most of the parameters. In addition, many groat, rolled oats, and oatmeal variables showed a significant year by crop interaction. Several grain variables were significantly interrelated but only two, moisture and amount of dark and damaged grains, had a strong correlation (r > 0.70) to rolled oat parameters, the former correlating negatively to crude fat and the latter positively with maximum viscosity value. However, some weaker (r < 0.70) negative associations were found such as those between kernel size value and β‐glucan content and water binding capacity of rolled oats. In general, the variables analyzed at different processing stages correlated strongly, indicating good retention of groat properties during processing. Various associations were found between the physicochemical parameters of rolled oats and sensory properties of oatmeal. In principal component analysis, factor 1 mostly represented rolled oat parameters such as crude fat, color values L and a, and oatmeal parameters such as toasted aromatics, coarseness, and size of swollen particles. Factor 2 represented properties that pertain to structure and water and rolled oats interactions. The cultivars were also grouped according to these properties. The results suggest that the rolled oat process deserves optimization on a cultivar basis, particularly when specific product properties such as good water binding capacity are required.     

Replacement of Shortening in Yellow Layer Cakes by Corn Dextrins

Shortening in a conventional yellow layer cake was replaced by maltodextrin (MD), amylodextrin (AD), octenyl succinylated amylodextrin (OSAD), or mixtures (MD+AD and MD+OSAD). The physical and sensory characteristics of the shortening‐free cakes were investigated. The specific gravity and viscosity of the cake batter, and the volume index of the baked cake were significantly reduced by MD, whereas the cake with added AD or OSAD showed a higher volume index than the control cake containing the shortening. An equivalent mixture of MD and AD, or MD and OSAD, however, produced cakes with a volume index and color defined as ΔE*(ab) that was similar to the control cake. Sensory evaluation revealed that the cakes containing AD or OSAD had significantly higher firmness than the control, but the cakes containing a mixture of MD and AD had firmness, springiness, and overall flavor scores similar to that of the control cake. According to instrumental texture profile analysis (TPA), MD addition, either alone or mixed with AD or OSAD, reduced firmness, whereas AD addition made the cake significantly firmer. When the shortening‐free cakes were stored for eight days at 4°C, TPA revealed greater changes in cake firmness and adhesiveness for MD alone. Cakes made from mixtures of dextrins (MD+AD and MD+OSAD) showed textural change with storage similar to that of the control cake, although the MD+AD cake remained softer than the control.