Offspring of first-generation hatchery steelhead trout (Oncorhynchus mykiss) grow faster in the hatchery than offspring of wild fish, but survive worse in the wild: Possible mechanisms for inadvertent domestication and fitness loss in hatchery salmon

Salmonid fish raised in hatcheries often have lower fitness (number of returning adult offspring) than wild fish when both spawn in the wild. Body size at release from hatcheries is positively correlated with survival at sea. So one explanation for reduced fitness is that hatcheries inadvertently select for trait values that enhance growth rate under the unnatural environment of a hatchery, but that are maladaptive in the wild environment. A simple prediction of this hypothesis is that juveniles of hatchery origin should grow more quickly than fish of wild origin under hatchery conditions, but should have lower survival under wild conditions. We tested that hypothesis using multiple full sibling families of steelhead (Oncorhynchus mykiss) that were spawned using either two wild parents (WxW) or two first-generation hatchery (HxH) parents. Offspring from all the families were grown together under hatchery conditions and under semi-natural conditions in artificial streams. HxH families grew significantly faster in the hatchery, but had significantly lower survival in the streams. That we see this tradeoff after only a single generation of selection suggests that the traits involved are under very strong selection. We also considered one possible alteration to the hatchery environment that might reduce the intensity of selection among families in size at release. Here we tested whether reducing the fat content of hatchery feed would reduce the variance among families in body size. Although fish raised under a low-fat diet were slightly smaller, the variation among families in final size was unchanged. Thus, there is no evidence that reducing the fat content of hatchery feed would reduce the opportunity for selection among families on size at release.

Effect of rearing system and sex on the composition and fatty acid profile of Andinoacara rivulatus meat from Ecuador

This study evaluated the influence of rearing system (cultured vs. wild rearing systems), and fish sex on carcass and flesh traits of A. rivulatus, raised in Ecuador. Three hundred mature specimens from A. rivulatus were captured, 150 from each origin. Slaughter yield and dress-out resulted similar for both rearing system, and average fillet yield for cultured fish was significantly higher than for wild fish, while cooking loss was significantly lower. Dress-out was significantly higher in females. Significant differences were found in wet percentage, ash, fat and protein content in both rearing systems, but only wet percentage was significantly affected by sex. Palmitic, oleic and arachidonic acids had the maximum percentage of saturated (SFA) and mono/poly unsaturated (MUFA/ PUFA) fatty acids, respectively. In cultured and wild fish, differentiations were also found in PUFA/SFA, docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA), atherogenicity (IA), and thrombogenicity (IT) indices, along with P, K, Mg, Cu and Fe. Sex and rearing system significantly influenced most of the analyzed characteristics of carcass and flesh of A. rivulatus. Fillet high yield and its proximate composition categorize A. rivulatus as a suitable food. These results provide valuable nutritional information about native species for consumers in Ecuador. Highlights: The rearing system (cultured vs. wild rearing systems), and fish sex affect the carcass and flesh traits of A. rivulatus. Fillet high yield and its proximate composition categorize A. rivulatus as a suitable food. The proximate composition of fillet from cultured A. rivulatus is more adequate than those of wild A. rivulatus. The cultured A. rivulatus contains higher n-3 and n-6 PUFA percentages and adequate n-3/n-6 ratio.

“Wild fish are a blessing”: changes in fishing practices and folk fish cuisine around Laguna Lake, Northern Philippines

Several coastal communities rely heavily on wild-caught fish for personal consumption and their livelihoods, thus being sensitive to the rapid global change affecting fish availability. However, in the last century, aquaculture has been increasingly adopted. To understand the uses and changes of wild-caught fish, we conducted 30 semi-structured interviews with fishers of Laguna Lake, Philippines. Fishermen, with up to 60 years’ experience, reported catching 31 fish species as a staple food. The taxa with the greatest variety of food uses were the farmed Oreochromis aureus, and the wild Channa striata and Cyprinus carpio. Fish was boiled, fried, grilled and dried, and over 20 different local dishes were reported. Fishers reported that local communities previously relied more on wild fish, while today a greater proportion of consumed fish comes from aquaculture fish species such as Oreochromis aureus and Hypophthalmichthys nobilis. Wild fish remains a crucial aspect of local gastronomic diversity, underpinning the biodiversity of the Laguna Lake, while also representing an important element for food sovereignty. The study stresses the need to sustain local ecological knowledge to ensure the ecological, social and economic sustainability of the communities.

Diary of Wimpy Fish: How to Grow Up in a Conservation Hatchery and Survive in the Real World

Conservation hatcheries are like luxury fish hotels that raise threatened and endangered fish that are nearing extinction in the wild. Raising fish in the controlled environment of the conservation hatchery usually takes away the issues that caused the population to dwindle in the first place. However, there is one problem: the fish get used to the conservation hatchery and become wimpy, meaning they become domesticated and do not do as well as wild fish in if they are returned to the natural environment. Managing the genes of hatchery fish is one way to block domestication and raise fish that are as close as possible to wild fish. In the San Francisco Estuary watershed, there are conservation hatcheries for the endangered delta smelt and winter-run Chinook salmon. Read on to learn about how these conservation hatcheries help hatchery fish be as tough as possible and survive in the wild.

Parasites prevalence which infecting freshwater fishes in Mulur Reservoir of Sukoharjo District, Indonesia

Iriansyah AH, Budiharjo A, Sugiyarto. 2020. Parasites prevalence infecting freshwater fishes in Mulur Reservoir of Sukoharjo District, Indonesia. Bonorowo Wetlands 10: 66-71. Mulur Reservoir is one of the natural fish habitats and consumption fish cultivation in Sukoharjo District, Indonesia. Excessive use of the reservoir area causes the decreasing of water quality which affects fish life sustainability, one of them can cause the fish susceptibility to infection by parasites. The purpose of this research was to identify the types of parasites which infect on consumption of fish in Mulur Reservoir and calculate the prevalence value. Samples were taken by purposive sampling for gourami (Osphronemus gouramy), tilapia (Oreochromis niloticus), betutu fish (Oxyeleotris marmorata), catfish (Clarias batrachus), and jambal (Pangasius djambal) 10 fishes for each type. The parts of fish infected by ectoparasites such as body mucus, fin mucus, head mucus, and gills were taken by scrapping and observed under a microscope with magnification between 100-400x. The results showed that 5 types of ectoparasites were Epistylis sp., Ichthyophthirius multifilis, Trichodina sp., Dactylogyrus sp., and Gyrodactylus sp. with an average prevalence of more than 50%. There are more ectoparasites in domesticated fish than in wild fish.