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This study investigated how 2+-year-old stocked pond-reared European graylings (Thymallus thymallus) acclimatised to a wild environment during six months (May–October 2019) after released. We examined the quantity and composition of lipids in the liver, muscles and visceral adipose tissues (VAT), as well as size parameters, condition factors and stomach contents. Our results showed a low post-stocking recapture rate (5.17%) of stocked fish after 6 months suggesting a poor acclimation to the wild environment. During the six months of monitoring, stocked fishes exhibited a sharp decrease in lipid content in all examined tissues, and, in the final month, lipid content was well below those of wild conspecifics. Stocked graylings preferred risky foraging behaviour and consumed numerous small drift preys with occasional hyperphagic events, thus experiencing strong bioenergetic challenges. Our study reveals that fish cultivated for extended periods struggle to acclimatise to the wild environment and that this commonly used stocking practice seems unsuccessful when aimed at strengthening wild grayling populations.

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The fiddler crab, Uca minax, has a complex lifecycle. Juvenile and adult stages occupy benthic habitats in estuaries and along the banks of tidally influenced rivers, and larval stages develop in the plankton of the coastal ocean. Bridging the gap between coastal planktonic and estuarine benthic habitats is the megalopal stage, also known as the postlarval settlement stage. Megalopae ride nocturnal flood currents into estuaries to locate appropriate settlement sites. In the process, they move from stable ocean salinities to the fluctuating environment of the estuary. In this study, we compare the osmotic tolerance of adult and megalopal U. minax to determine if it is equivalent in both stages of life. Adult crabs were collected from benthic habitats in the Winyah Bay (oligohaline), North Inlet Estuary (euhaline) and the Great Pee Dee River (oligohaline) in South Carolina. Megalopae were collected from the Pee Dee and Waccamaw rivers using light traps. Both adult and megalopal U. minax were subjected to 12 concentrations of seawater between 40 3320 mOsm/Kg (pH 8.0). Survivorship was assessed in adults after 5 days and in megalopae after 24 hours of osmotic challenge. Both adults and megalopae had excellent survival in the lowest concentrations. The upper lethal concentration (ULC50) was 1384, 1350 and 2200 mOsm/kg for adults from The Great Pee Dee, Winyah Bay, and North Inlet Estuary, respectively. Megalopae from the Pee Dee and Waccamaw rivers showed an ULC50 of 1246 mOsm/kg. Since megalopae and adults from oligohaline habitats have similar osmotic tolerance, this suggests that the settlement stage of U. minax has well developed osmoregulation capabilities.

The complexities of non-target effects of registered pesticides on biocontrol agents (BCAs) hinder the optimization of integrated pest management programs in agriculture. The wealth of literature on BCA-pesticide compatibility allows for the investigation of factors influencing BCA susceptibility and the generalized impacts of different pesticides. We conducted a meta-analysis using 2088 observations from 122 published articles to assess non-target effects on two phytoseiid species (Neoseiulus californicus and Phytoseiulus persimilis), a parasitoid (Encarsia formosa), and two microbial BCAs (Trichoderma harzianum and Metarhizium anisopliae). We explored the contributions of bioassay factors (exposure duration, temperature, test methods, mode of actions (MOA), and type of pesticide), and simulated effects of compatibility on target pests. MOA groups 21 and 6 were the most harmful to predatory mites and E. formosa, increasing mortality during pesticide-BCA compatibility. Exposure duration, temperature, and test methods were identified as the most influential factors increasing mortality in phytoseiids during pesticide exposure. Insecticides and fungicides were the most represented and harmful groups to BCAs. Although most bioassays were conducted at room temperature, temperatures between 21 and 22 °C were the most harmful to phytoseiids and E. formosa during toxicity assays. Exposure durations of 1-3 days (54-85 %) for predators/parasitoids and 1-5 days (>50 %) for microbial BCAs highlight the lack of data on long-term impacts. In assessing pesticide impacts on target pests, pesticides with compatible concentrations above mean LC50 values were more effective. This study not only identified compatibility trends but also highlighted factors responsible for discrepancies in results and knowledge gaps that need to be addressed., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Long-chain polyunsaturated fatty acids (LC-PUFA) like arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3), and docosahexaenoic acid (DHA, 22:6n-3) constitute one-third to half of fish sperm lipids. Fish sperm is rich in phospholipid (PL)-primarily phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin. DHA is generally the most abundant LC-PUFA in each PL class, followed by competition between ARA and EPA. While the total n-6: n-3 PUFA ratio does not correlate significantly with sperm biomechanics, LC-PUFA do. DHA positively influences sperm biomechanics, while ARA and EPA may be negatively associated. Fish sperm maintains lower (≤1) total n-6 PUFA per unit of n-3 PUFA but keep a higher (>1) ARA per unit EPA. A weak dietary influence on sperm EPA and DHA exists but not on ARA. The DHA: EPA ratio in fish sperm is often >1, though values <1 occur. Certain species cannot fortify DHA sufficiently during spermatogenesis, diverging through whole genome duplications. Fish sperm can show ARA: EPA ratios greater or less than 1, due to shifts in prostaglandin pathways in different evolutionary eras. DHA-rich PL bilayers provide unique packing and fusogenic properties, with ARA/EPA-derived eicosanoids guiding sperm rheotaxis/chemotaxis, modulated by DHA-derived resolvins. Docosapentaenoic acid (DPA, 22:5n-3) sometimes substitutes for DHA in fish sperm., Competing Interests: Declaration of competing interest Authors declare no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

A highly pH-responsive gelatin film incorporating purple cabbage anthocyanin (PCA) and chondroitin sulphate (CS)/tannic acid (TA) was developed. Co-pigmentation of PCA via CS/TA improved its photothermal stability and visibility of color change in gelatin film. The morphological and structural properties of CS-PCA and TA-PCA films revealed that a more stable network was formed as new hydrogen bonds were generated by the co-pigmentation. Meanwhile, the co-pigmentation improved film's mechanical and hydrophobic properties, expressed as higher tensile strength (16.65 and 17.97 Mpa) and lower water vapor permeability (1.45 and 1.41) in CS-PCA and TA-PCA films, compared to PCA film. CS-PCA and TA-PCA films showed distinct color transitions for chilled fish fillets during storage. Total color difference (ΔE) of CS-PCA and TA-PCA films correlated well with the deterioration indexes of total volatile base nitrogen (TVB-N). All the results provided a novel pH-sensitive intelligent packaging strategy by co-pigmenting CS/TA with PCA for freshness monitoring., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier Ltd.)

The study provides a descriptive understanding of when fish (Cyprinus carpio model) are the source or sink of phosphorus. Dissolved reactive phosphorus (DRP; PO 4 -P) losses (51.1 ± 5.9 % of intake-P) increase at excess of bioavailable P (>0.83 g 100 g -1 dry matter, DM fed) or when food (digestible) N:P mass ratio (≤4.4:1) approaches organismal storage threshold (~4:1). This is known, however, even at a sub-threshold food P content (0.57 g 100 g -1 DM) and food N:P mass ratio (7.3:1), DRP losses (57.8 ± 4.5 % of intake-P) may be extraordinary if two indispensable amino acids are biologically insufficient (lysine ≤1.43 g, methionine ≤0.39 g 100 g -1 DM fed). Given that methionine and lysine are sufficient, DRP losses cease (≈0 %) and even some P from water is absorbed, given there is support from non-protein energy (NPE). Insufficient NPE (<180 kcal 100 g -1 DM fed) may drive DRP losses (81.6 ± 4.3 % of intake-P) beyond expected levels (46-59 % of intake-P) at a given food P content (0.91 g 100 g -1 DM). Natural food seldom fulfills low P, high lysine + methionine, and high NPE contents simultaneously, thus keeping fish in a perpetual P recycling for algae (scaleless carp > scaly carp). Such P recycling ceases only during basal metabolism. During feeding state, the richness of lysine + methionine bound N and lipid + carbohydrate bound C in the food base may enhance the fishes' threshold of P storage. P storage can be diminished when they are insufficient. We show that for fish, the decision of P recycling or not recycling (for algae) may change based on the supply of specific fractions of N or C from the food web or metabolic variations (basal metabolism, presence of scales). NOVELTY STATEMENT: The ecological stoichiometry theory is better connected to fish nutritional bioenergetics for better understanding and biomanipulation of eutrophication processes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A digestibility enhancing effect of natural food on stomachless fish model (Cyprinus carpio) was verified by fluorogenic substrate assays of enzymatic activities in experimental pond carp gut flush and planktonic food over a full vegetative season. Then compared with size-matched conspecific grown artificially (tank carp) and an advanced omnivore species possessing true stomach (tilapia, Oreochromis niloticus). Results suggested activities of digestive enzymes (except amylolytic) were significantly higher in pond carp (p ≤ 0.05) than in the size-matched tank carp. Even compared to tilapia, pond carp appeared superior (p < 0.05; proteolytic or chitinolytic activities) or comparable (p > 0.05; phosphatase or cellulolytic activities). Amylolytic, chitinolytic, and phosphatases activities in pond carp gut significantly increased (p ≤ 0.01) over season. Several orders-of-magnitude higher enzymatic activities were detected in planktonic natural food than expressed in carp gut. Amino acid markers in planktonic food revealed a higher share of zooplankton (microcrustaceans), but not phytoplankton, synchronized with higher activities of complex polysaccharide-splitting enzymes (cellulolytic and chitinolytic) in fish gut. Periods of clear water phase low in chlorophyll-a and nutrients, but high in certain zooplankton (preferably cladocerans), may create a synergistic digestibility effect in pond carp. We conclude aquatic ecosystem components (natural food, water, microbiota) enhance fishes' hydrolyzing capabilities of C/N/P macromolecules and even their complex polymers such as cellulose, chitin, and maybe phytate (to be validated), to the extent that being stomachless is not an issue. Aquatic nutritional ecologists may consider that laboratory-based understandings of digestibility may underestimate digestion efficiency of free-ranging fish in ponds or lakes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)