Effects of substitution of dietary fish oil with a blend of vegetable oils on liver and peripheral blood leucocyte fatty acid composition, plasma prostaglandin E2 and immune parameters in three strains of Atlantic salmon (Salmo salar)

Duplicate groups of three genetic strains of Atlantic salmon smolts were cultured on diets containing either fish oil (FO) or a blend of vegetable oils (VO). Fatty acid compositions of liver and peripheral blood leukocytes were compared. The effect of different strains and diets on innate immune parameters and plasma prostaglandin E2 were also measured. Two strains were selected as being either “fat” or “lean” in terms of muscle adiposity. The third strain was a commercial stock (MH). Total replacement of dietary FO with VO resulted in reduced docosahexaenoic (DHA; 22:6n-3) and eicosapentanoic acids (EPA; 20:5n-3) in liver, while oleic (18:1n-9), linoleic (18:2n-6) and α-linolenic (18:3n-3) acids were all increased in VO-fed fish. Fatty acid compositions of blood leucocytes showed similar changes. Evaluation of innate immune function showed that in the fat strain circulating leucocytes were significantly lower in VO fish. The lean strain also had significantly higher serum lysozyme activity than MH fish. Reduced haematocrit was seen in VO lean fish compared to FO lean fish. This study provides evidence of strain-induced differences in liver and leukocyte fatty acid compositions and innate immunity in Atlantic salmon fed either FO or VO-based diets

Adrenocorticotrophic hormone-stimulated cortisol release by the head kidney inter-renal tissue from sea bream (Sparus aurata) fed with linseed oil and soyabean oil

The mode of action of highly unsaturated fatty acids (HUFA) in regulating gilthead sea bream (Sparus aurata) head kidney (HK) cortisol production was studied through in vitro trials using a dynamic superfusion system. Fish were previously fed with different diets containing several inclusion levels of linseed oil (LO) or soyabean oil (SO) for 26 weeks. Five diets were tested; anchovy oil was the only lipid source for the control diet (fish oil, FO) and two different substitution levels (70 and 100 %) were tested using either LO or SO (70LO, 70SO, 100LO and 100SO). Fatty acid compositions of the HK reflected the dietary input, thus EPA, DHA, arachidonic acid and n-3 HUFA were significantly (P,0·05) reduced in fish fed vegetable oils compared with fish fed the FO diet. Feeding 70 or 100% LO increased significantly (P,0·05) cortisol release in HK after stimulation with adrenocorticotrophic hormone (ACTH), while feeding SO had no effect on this response. Cortisol stimulation factor (SF) was increased in fish fed the 70LO and 100LO diets compared with fish fed the control diet. Moreover, eicosanoid inhibition by incubating the HK tissue with indomethacin (INDO) as a cyclo-oxygenase (COX) inhibitor, or nordihydroguaiaretic acid (NDGA) as a lipoxygenase (LOX) inhibitor, significantly reduced (P,0·05) the cortisol release after ACTH stimulation in the 70LO and 100LO diets. Cortisol SF was reduced in the FO, 70LO and 100LO diets when incubating the HK with INDO or NDGA, while it was increased in the 70SO diet. The present results indicate that changing the fatty acid profile of gilthead sea bream HK by including LO and/or SO in the fish diet affected the in vitro cortisol release, and this effect is partly mediated by COX and/or LOX metabolites

Recent Salmon Declines: A Result of Lost Feeding Opportunities Due to Bad Timing?

As the timing of spring productivity blooms in near-shore areas advances due to warming trends in global climate, the selection pressures on out-migrating salmon smolts are shifting. Species and stocks that leave natal streams earlier may be favoured over later-migrating fish. The low post-release survival of hatchery fish during recent years may be in part due to static release times that do not take the timing of plankton blooms into account. This study examined the effects of release time on the migratory behaviour and survival of wild and hatchery-reared coho salmon (Oncorhynchus kisutch) using acoustic and coded-wire telemetry. Plankton monitoring and near-shore seining were also conducted to determine which habitat and food sources were favoured. Acoustic tags (n = 140) and coded-wire tags (n = 266,692) were implanted into coho salmon smolts at the Seymour and Quinsam Rivers, in British Columbia, Canada. Differences between wild and hatchery fish, and early and late releases were examined during the entire lifecycle. Physiological sampling was also carried out on 30 fish from each release group. The smolt-to-adult survival of coho salmon released during periods of high marine productivity was 1.5- to 3-fold greater than those released both before and after, and the fish's degree of smoltification affected their downstream migration time and duration of stay in the estuary. Therefore, hatchery managers should consider having smolts fully developed and ready for release during the peak of the near-shore plankton blooms. Monitoring chlorophyll a levels and water temperature early in the spring could provide a forecast of the timing of these blooms, giving hatcheries time to adjust their release schedule

Challenges and Opportunities in Finfish Nutrition

Much of the criticism leveled at aquaculture (e.g., dependency on animal-derived feedstuffs, nutrient-laden effluent discharges, and increased organic contamination in edible products) can be traced to the feeds in use. Accordingly, finfish nutritionists are being challenged to formulate feeds that not only meet the nutritional requirements of livestock but also minimize production costs, limit environmental impacts, and enhance product quality. These challenges not only add considerable complexity to finfish nutrition but also afford opportunities to avoid some of the mistakes made by other industries in the past. From a review of the current status of finfish nutrition with respect to major nutrient classes, we comment on future opportunities and promising avenues of research. Alternative protein sources, specifically those derived from marine bycatch, plants, and microbes, are discussed, as well as methods to facilitate their implementation in finfish feeds. Dietary lipid, its role in fish bioenergetics and physiology, and quality of aquaculture products is reviewed with special emphasis on alternative lipid sources and finishing diets. Carbohydrates and fiber are discussed in terms of nutrient-sparing, least-cost diet formulation and digestive physiology. Micronutrients are reviewed in terms of current knowledge of requirements and, along with other dietary immunostimulants, are given further consideration in a review of nutriceuticals and application in finfish feeds. The status of nutritional research in new aquaculture species is also outlined. By integrating classical approaches with emerging technologies, dietary formulations, and species, finfish nutritionists may identify means to increase production efficiency and sustainability and provide for the continued success of aquaculture

A Synthesis of Tagging Studies Examining the Behaviour and Survival of Anadromous Salmonids in Marine Environments

This paper synthesizes tagging studies to highlight the current state of knowledge concerning the behaviour and survival of anadromous salmonids in the marine environment. Scientific literature was reviewed to quantify the number and type of studies that have investigated behaviour and survival of anadromous forms of Pacific salmon (Oncorhynchus spp.), Atlantic salmon (Salmo salar), brown trout (Salmo trutta), steelhead (Oncorhynchus mykiss), and cutthroat trout (Oncorhynchus clarkii). We examined three categories of tags including electronic (e.g. acoustic, radio, archival), passive (e.g. external marks, Carlin, coded wire, passive integrated transponder [PIT]), and biological (e.g. otolith, genetic, scale, parasites). Based on 207 papers, survival rates and behaviour in marine environments were found to be extremely variable spatially and temporally, with some of the most influential factors being temperature, population, physiological state, and fish size. Salmonids at all life stages were consistently found to swim at an average speed of approximately one body length per second, which likely corresponds with the speed at which transport costs are minimal. We found that there is relatively little research conducted on open-ocean migrating salmonids, and some species (e.g. masu [O. masou] and amago [O. rhodurus]) are underrepresented in the literature. The most common forms of tagging used across life stages were various forms of external tags, coded wire tags, and acoustic tags, however, the majority of studies did not measure tagging/handling effects on the fish, tag loss/failure, or tag detection probabilities when estimating survival. Through the interdisciplinary application of existing and novel technologies, future research examining the behaviour and survival of anadromous salmonids could incorporate important drivers such as oceanography, tagging/handling effects, predation, and physiology

Wheelchair and seating service provision in the Republic of Ireland: exploring service users’ perspectives

Purpose: To explore the perspectives of service users availing of wheelchair and seating service provision in the Republic of Ireland, within the context of muscular dystrophy. Method: Four participants availing of wheelchair and seating service provision were interviewed using a semi-structured, open-ended interview protocol. Three participants were adult wheelchair users with muscular dystrophy and one a wheelchair associate, the mother of an adolescent with muscular dystrophy. The research was informed by a qualitative research methodology and data analysed using thematic analysis. Results: Three themes emerged following data analysis: ‘becoming and being a wheelchair user: progression, participation and provision’, ‘influences on service user experience: resources and rapport’ and ‘navigating the system: support, self-advocacy and suggestions’. Participants gave their perspectives of the personal impact of muscular dystrophy and wheelchair use, provided examples of what influenced their experiences of service provision and described how they themselves navigated the services of which they availed. Conclusion: Areas of consideration by occupational therapists practicing within the realms of wheelchair and seating service provision were highlighted, such as the importance of understanding the lived experience of service users and establishing sufficient therapeutic rapport. Funding, waiting times and client-therapist relationships were highlighted as areas that appeared to impact upon service user satisfaction. The consequence of inadequate service provision is discussed as is the importance of supporting the implementation of best practice guidelines and the creation of governmental policy regarding personal mobility in the Republic of Ireland