Iain K. Berrill

Photoperiodic effects on precocious maturation, growth and smoltification in Atlantic salmon, Salmo salar

Abstract Current Atlantic salmon farming practice induces early smoltification with artificial photoperiod regimes, however the importance of these photoperiods on parr maturation and interactions with smoltification are poorly understood. These questions were addressed in the present investigation, which examined the effects of photoperiod manipulation on the development, maturation and smoltification of individually tagged parr. Approximately 9000 salmon parr from a high grilsing stock were exposed to continuous light (LL) from first feeding. Three sub-groups of 2400 parr, each sub-group in triplicate tanks, were then exposed to an 8-week “winter photoperiod” (LD 10:14) starting on either the 18th May, the 9th August or the 20th September (defined, respectively, as the May, August and September groups). Following the artificial winter, each group was returned to LL. A fourth group of 1600 fish was maintained in replicate tanks on LL throughout. The highest levels of maturation (approx. 20%) were recorded in the May group. August and September groups showed low levels of maturity ( It is concluded that the photoperiod to which parr are exposed early in their life acts as an important trigger for precocious maturation but does not necessarily phase shift the endogenous rhythm which is thought to control its timing. Smoltification is strongly influenced by the timing of exposure to winter photoperiod with clear evidence indicating that maturation and smoltification are not mutually exclusive processes.

HOW TO MEASURE THE ECONOMIC IMPACTS OF CHANGES IN GROWTH, FEED EFFICIENCY AND SURVIVAL IN AQUACULTURE

In this article we introduce a variety of bio-economic models that can be used to calculate the economic benefits associated with improved productivity in aquaculture. In the aquaculture industry, three important biological productivity factors are growth, survival and feed efficiency. The profitability of improving productivity factors, especially growth, is highly dependent upon the cost factor structure, production system, its constraints and other factors within the supply chain. Therefore we present a number of different bio-economical models that can be used to robustly assess the economic impacts in different production environments. These models are introduced with case examples across a range of aquaculture species and production systems. We calculate changes in profitability through a reduction in production costs and any potential increases in product price premiums via the use of weight dependent unit profit as the outcome in cost-benefit analysis, so that results may be expanded to cover different volumes.

Mortality and fish welfare

Mortality has received insufficient attention as a fish welfare topic. Here, we aim to prompt fish farming stakeholders to discuss fish mortalities in relation to welfare. Mortality in farmed fish populations is due to a variety of biotic and abiotic causes, although it is often difficult to differentiate between underlying and immediate causes of mortality. Most mortality appears to occur during episodes associated with disease outbreaks and critical periods (in development or production). Most causes of mortality can be assumed to be associated with suffering prior to death. As mortality rates in farmed fish populations are suspected to rank amongst the highest in commonly farmed vertebrate species, mortality should be a principal fish welfare issue. Long-term mortality rates can be used as a retrospective welfare performance indicator and short-term mortality rates as an operational welfare indicator. Scrutiny of mortality records and determining causes of death will enable action to be taken to avoid further preventable mortality. The welfare performance of fish farms should only be judged on levels of predictable and preventable mortality. Fish farmers will already be monitoring mortality due to commercial and legal requirements. As profitability in fish farming is directly linked to survival, confronting mortality should ultimately benefit both fish and farmers.

BIO-ECONOMIC COSTS AND BENEFITS OF USING TRIPLOID RAINBOW TROUT IN AQUACULTURE: REDUCED MORTALITY

Analysis of data collected from rainbow trout farms in the United Kingdom found that mortality levels in triploid rainbow trout were lower than those in diploids. The consequences of rearing triploids, as opposed to diploids, as an intervention to reduce mortality in the U.K. trout farming industry were quantified using a bio-economic model. The model showed that growing triploids could be more profitable than growing diploids, and this was achieved through improvements in productivity (in terms of better survival) and potential for increased product value, and despite the extra costs attributed to purchasing triploid fingerlings.

THE BIO-ECONOMIC COSTS AND BENEFITS OF IMPROVING PRODUCTIVITY AND FISH WELFARE IN AQUACULTURE: UTILIZING CO2 STRIPPING TECHNOLOGY IN NORWEGIAN ATLANTIC SALMON SMOLT PRODUCTION

High dissolved CO2 levels in tank water are potentially detrimental to the production and welfare of Atlantic salmon smolts in Norwegian hatcheries. A potential welfare action for reducing CO2 levels is to deploy CO2 stripping technology. The economic consequences of using this approach were modelled using a bio-economic decision analysis tool. Results from the model showed that farmers can improve fish welfare and their profits by utilizing CO2 stripping technology, as costs of implementing the welfare action were less than the potential bio-economic benefits that can be achieved through improved productivity and any potential added value for improving the welfare of smolts.

MODELING THE ECONOMIC IMPACT OF WELFARE INTERVENTIONS IN FISH FARMING—A CASE STUDY FROM THE U.K. RAINBOW TROUT INDUSTRY

Actions that aim to improve animal welfare are likely to involve costs for the producer, although at the same time such actions may improve the profitability of production. In this article we introduce a quantitative bio-economical approach for estimating the economic consequences for improving animal welfare in the aquaculture industry; for farmers and the industry as a whole. The decision tool can be used with different welfare indicators, different species and production systems. It can be used to rank the economic consequences of different techniques that aim to improve welfare. We illustrate the decision tool with a case study relating to the use of triploids in rainbow trout farming. We highlight the probability how the benefits gained from changes in bio-economical productivity factors, and consumers’ willingness to pay can overcome the costs associated with implementing a specific welfare intervention.

Achieving consensus on current and future priorities for farmed fish welfare: a case study from the UK

The welfare of farmed fish has attracted attention in recent years, which has resulted in notable changes within the aquaculture industry. However, a lack of communication between stakeholders and opposing ethical views are perceived as barriers to achieving consensus on how to improve farmed fish welfare. To address these issues, we developed an interactive approach that could be used during stakeholder meetings to (1) improve communication between different stakeholder groups, (2) build consensus on priorities for farmed fish welfare and (3) establish mechanisms to address welfare priorities. We then applied this approach during a meeting of stakeholders to identify current and future priorities for farmed fish welfare in the UK. During the meeting in the UK, stakeholders initially identified 32 areas that they felt were in need of development for future improvements in farmed fish welfare. These were further refined via peer review and discussion to the seven most important “priority” areas. Establishing a “better understanding of what good fish welfare is” emerged as the highest priority area for farmed fish welfare. The second highest priority area was “the need for welfare monitoring and documentation systems”, with mortality recording proposed as an example. The other five priority areas were “[improved understanding of] the role of genetic selection in producing fish suited to the farming environment”, “a need for integration and application of behavioural and physiological measures”, “the need for a more liberal regime in Europe for introducing new medicines”, “a need to address the issues of training existing and new workers within the industry”, and “ensuring best practise in aquaculture is followed by individual businesses”. Feedback from attendees, and the meeting outputs, indicated that the approach had been successful in improving communication between stakeholders and in achieving consensus on the priorities for farmed fish welfare. The approach therefore proved highly beneficial for future improvements in fish welfare in the UK.

A MULTI-DISCIPLINARY FRAMEWORK FOR BIO-ECONOMIC MODELING IN AQUACULTURE: A WELFARE CASE STUDY

This article summarizes the framework that translated data from multiple disciplines into a bio-economic decision tool for modeling the costs and benefits of improving fish welfare in commercial aquaculture. This decision tool formed the basis of a recent EU research project, BENEFISH which was funded via the European Commissions Sixth Framework (FP6) initiative. The bio-economic decision model can incorporate biological data, productivity data, micro (farm) and macro (industry) level economic data, and consumer marketing and business to business data. It can identify areas for potential added value that might be achieved by improving fish welfare across a range of species and husbandry systems within European aquaculture. This article provides a brief overview of the minimum data requirements for successfully modeling the bio-economic impacts of improvements in farmed fish welfare using the model developed during the BENEFISH project. It also highlights potential bottlenecks and the minimum prerequisites for each potential data set to be used for successful modeling.