Warm Water Can Trigger Deformities In Farmed Fish

The finding is part of the FINE FISH ('Reduction of malformations in farmed fish species') project, which received EUR 3.02 million under the SME (small and medium-sized enterprise) cross cutting activity of the Sixth Framework Programme (FP6). Results of the study were recently published in BMC (BioMed Central) Physiology.

Spinal disorder, which can occur relatively frequently among intensively farmed fish, presents an important health and productivity challenge for the aquaculture sector. Unfortunately, there is a lack of information on the underlying molecular mechanisms involved in bone deformities in fish and other farmed animals which would help curb this problem.

The team of four scientists from Chile and Norway involved in the study wanted to improve on this knowledge base by studying the bone metabolism and pathogenesis of vertebral fusions in Atlantic salmon (Salmo salar).

The researchers reared 400 juvenile salmon in water at a temperature of 10°C and a further 400 at a temperature of 16°C. Salmon farmers often use warmer water to increase fish growth rates, and the two tanks with the two temperatures were observed over a period of time to document any ensuing differences as a result of temperature.

Indeed, the study showed that bone and cartilage production was disrupted when temperatures were elevated. This resulted in an increased rate of deformities for the 16°C group. This group of fish grew faster, but more than a quarter (28 per cent) was found to show some signs of skeletal deformity (compared to eight per cent of the fish in the 10°C group).

Co-author of the study Dr Harald Takle from the Norwegian University of Life Sciences in Norway and AVS Chile explained that the results 'strongly indicate that temperature-induced fast growth is severely affecting gene transcription in osteoblasts and chondrocyte bone cells, leading to a change in the tissue structure and composition'.

The researchers conducted further studies specifically on the salmon with the vertebral abnormalities and found that the deformity process involves molecular regulation and cellular changes similar to those found in intervertebral disc degeneration in mammals.

The findings add to a considerable body of work produced under the FINE FISH project. FINE FISH generated new practical knowledge on how to reduce the incidence of malformations in the major fish species used in European aquaculture production, and how to apply this to the professional sector, made up largely of SMEs.

Eleven of the 20 partners that committed time under FINE FISH were SMEs. Mr Courtney Hough from the Federation of European Aquaculture Producers (FEAP), FINE FISH's coordinating partner, explained that the direction of the research, the presentation of results, and the field trials were shaped by the SMEs' contributions and desire to be involved. In fact, the impetus for FINEFISH originated from a hatchery workshop, where the SME participants themselves requested that such a project be realised.

'The focus given to application of results in a practical manner to the SME hatchery sector was of extreme importance to the FEAP, whose key interest was to have clear recommendations for the improvement of performance in the European fish hatchery sector,' Mr Hough told Research Headlines.

As a result, there are several tools available on the project's website including the FINE FISH diagnostic manuals for individual species (bass and bream, industrial monitoring, cod, trout, and salmon) and material used in the series of training courses. Mr Hough noted that the manual, 'Control of Malformations in Fish Aquaculture: Science and Practice', was one of the key products developed under the project.

Another important outcome was the establishment of new professional partnerships between SMEs and the research sector, several of which have moved on to explore new challenges.

'One of the key messages from this project was that genuine collective research requires building a solid bridge between the research and SME participants,' Mr Hough added. 'This means active participation and commitment within such projects as well as understanding their limits.'

FEAP estimates that 650 000 tonnes of fish are farmed in the EU annually (compared to 60 000 tonnes in 1970). Within Europe as a whole, the total production is more than 1.6 million tonnes. Norway is a major contributor to Europe's aquaculture sector with over 860 000 tonnes of salmon and trout produced each year.

Hatcheries produce fertilised eggs, larvae, fry and juveniles that represent the valuable starting materials for the majority of European fish farmers.