Location: Cool and Cold Water Aquaculture ResearchTitle: Influence of long term ammonia exposure on Atlantic salmon (Salmo salar L.) parr growth and welfare Author
|Terjesen, Bendik Fyhn|
Submitted to: Aquaculture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2011
Publication Date: 5/7/2012
Citation: Kolarevic, J., Selset, R., Felip, O., Good, C., Snekvik, K., Takle, H., Ytteborg, E., Baeverfjord, G., Asgard, T., Terjesen, B. 2012. Influence of long term ammonia exposure on Atlantic salmon (Salmo salar L.) parr growth and welfare. Aquaculture Research. 1-16. DOI: 10.1111/j.1365-2109.2012.03170.x. Interpretive Summary: Ammonia is the main nitrogenous waste product in most teleosts, and is excreted through the gills to the surrounding water. Un-ionized ammonia can be toxic to fish in sufficient concentrations, and is a critical parameter when establishing maximum water quality limits during recirculation aquaculture system design. While acute ammonia toxicity to fish has been studied, longer-term research investigating chronic exposure to low-level un-ionized ammonia is lacking in the scientific literature. We exposed Atlantic salmon parr to four sublethal concentrations of un-ionized ammonia at two different feeding levels for 105 days. We found that higher levels of un-ionized ammonia, combined with full-ration feeding, reduced parr growth rates and was associated with higher prevalence of subclinical gill pathologies; however, these early effects were not persistent and by study's end no significant differences in fish size or gill damage were noted. Furthermore, the subsequent parr-smolt transformation did not appear to be influenced by the ammonia and/or diet treatments. We conclude that long-term exposure to un-ionized ammonia levels of up to 35 ug/L, either with full or reduced feed ration, did not affect parr size or welfare through 105 days. These results can assist aquaculturists in considering water quality limits when designing fish culture systems.
Technical Abstract: The objective of this study was to determine the long-term effects of ambient unionized ammonia nitrogen (NH3-N) combined with different feeding regimes on Atlantic salmon Salmo salar L parr growth, welfare and smoltification. Previous studies on the parr stage of Atlantic salmon have mostly focused on acute exposure, or at low temperatures. Atlantic salmon parr were exposed for 105 days (at 12 deg C, pH 6.8) to four sublethal ammonia concentrations ranging from 0.1 to 35 micro gram L-1NH3-N (0.1–25 mg L-1TAN) at two feeding levels: full feed strength (+20% overfeeding) and 1/3 of full feed strength. After 21 days, it was observed that 32 micro gram L-1NH3-N reduced growth rate of parr fed full ration, but this effect was not evident at the end of the exposure. Feed utilization was not affected by ammonia exposure at any sampling point. Increasing ammonia levels were associated with a higher prevalence and severity of gill damage at 22 days but not at the end of the exposure. The examination of welfare indicators revealed only a few pathologies, not related to ammonia exposure. In addition, higher ammonia concentrations did not appear to influence the development of hypo-osmoregulatory ability during parr-smolt transformation.