Adding fish waste to the diet of Iceland scallop Chlamys islandica: effects on feeding and reproductive ability

Abstract

Organic enrichment from fish farming may impact benthic species and habitats in adjacent areas. Norwegian salmon farming is continuously growing, but, due to area conflicts and severe sea-lice problems in the western areas, growth of the industry is focused in the northern areas. Knowledge is scarce on how an increase in fish farming will impact Arctic and subarctic species and habitats. One such species is the Iceland scallop Chlamys islandica, distributed from the Lofoten Islands in Nordland County to the Varangerfjord in Troms and Finnmark County. To study the impact of fine-particle fish faeces on feeding and reproductive ability in adult Iceland scallop, particles <41 µm of finfish waste were added to the diet. Effects were tested via short-term (weeks) feeding studies using 2 diets, 100% cultured algal species and a 50% mix of algae and fish waste. In addition, a 100% fish waste diet was used to study longer-term effects on reproductive ability (months). Feeding (% particle clearance and feeding rate) on the microalgae diet tended to be higher than that on the diet containing fish waste, but the difference was significant only in 2 out of 4 cases. We did not find any effect of diets on reproductive ability (gonad development and fatty acid profiles) of scallops. Lack of knowledge on sufficient food levels for gonad maturation in this species may have affected the results. We suggest that future work includes the transplant of scallops from a reference site to fish production sites and that investigations begin immediately after spawning early in scallop gonad development.