Tank size and fish management history matters in experimental design

Abstract

To investigate the questions: (1) does tank size affect fish performance; (2) does tank size prior to an experiment affect later fish performance and (3) how does performance in experimental tanks compare with rearing in industry-scale cages, Atlantic salmon smolts were acclimatized to 190, 3 or 0.9 m 3 tanks (Phase 1; 1.5 months) before redistributed to Phase 2 for 5 months. Question 1: fish in 190 m 3 tank were redistributed to 0.9 m 3 (190 m 3 ? 0.9 m 3 ), 3 m 3 (190 m 3 ? 3 m 3 ), or 103 m 3 (190 m 3 ? 103 m 3 ) tanks. Question 2: fish in 0.9 m 3 tanks were redistributed to 3 m 3 tanks (0.9 m 3 ? 3 m 3 ), and compared to fish from 190 m 3 tank (190 m 3 ? 3 m 3 ). Question 3: fish were placed directly in 3 m 3 tanks, not moved (3 m 3 ? 3 m 3 ), and compared to reference sea cages. Phase 2 mortality: 190 m 3 ? 0.9 m 3 (46%), 190 m 3 ? 3 m 3 (29%), 190 m 3 ? 103 m 3 (19%), 3 m 3 ? 3 m 3 and 0.9 m 3 ? 3 m 3 (<5%). Most mortality happened shortly after transfer. Our study suggests tank size dependent performance, based on growth and feed intake that increased with tank size. 190 m 3 ? 103 m 3 fish were more active than 190 m 3 ? 0.9 m 3 and 190 m 3 ? 3 m 3 fish. 190 m 3 ? 103 m 3 tanks had lowest relative variance. Previous tank scale history affected survival, since 0.9 m 3 ? 3 m 3 fish showed higher survival than 190 m 3 ? 3 m 3 fish. However, previous scale history did not affect growth rate, feed intake or somatic indexes. Fish performance in 3 m 3 ? 3 m 3 tanks did not differ from the reference sea cages. However, fish in 103 m 3 tanks performed better than reference cages, suggesting potential for improved commercial production. This study demonstrates that management practices can influence fish performance and should be taken into account when designing experiments.

Modelling growth performance and feeding behaviour of Atlantic salmon (Salmo salar L.) in commercial-size aquaculture net pens: Model details and validation through full-scale experiments

“…The experiments conducted by Espmark et al (in press) illustrated how differences in physical scale (i.e. geometric size) or scaling histories will affect Atlantic salmon performance in indoor tank facilities.…”

“…Earlier studies have found that the growth of Atlantic salmon may be affected by factors such as tank size and current speed ( Boeuf and Gaignon, 1989 ), and fish density ( Refstie and Kittelsen, 1976 ), which are all relevant elements when considering scaling effects. ( Espmark et al, in press ) focused on assessing this question more directly by conducting an experiment where a set of land based tanks of different geometric sizes (0.9, 3, 103 and 190 m 3 ) were stocked with Atlantic salmon smolts from a common genetic strain and cohort. The main aim of that study was to investigate whether there were differences in fish performance (i.e.…”

Feed intake in Atlantic salmon fed with or without surface spreading of feed

“…Compared to experiments in sea cages, a tank experiment has the advantages that spreading of feed, feed intake and growth can be measured with high accuracy, and it can be run at a relatively low cost. Data from small scale studies are not necessarily valid for large scale conditions (Espmark et al, 2017). As for all trials, the data from the present study are only representative for the conditions used in this study.…”

“…In tanks, the behavior is restricted by the volume of the tank. Volume and design of the tanks have been shown to affect feed intake and growth in salmon (Espmark et al, 2017;Føre et al, 2018).…”

The Effect of Temperature on the Physiological Condition and Immune-Capacity of European Lobsters (Homarus gammarus) During Long-Term Starvation

“…We considered this experimental set-up to be not only more industry relevant but also necessary to ensure the welfare of the animals over the 24-week experimental period. Recently, Espmark et al (2017) highlighted the negative effects of keeping fish in smaller tanks, i.e., reduced food intake and growth. Once allocated, the temperature in each tank was adjusted over 72 h to one of three temperatures: 4, 8, and 12 • C (two tanks per temperature) and maintained in a flowthrough system at those temperatures, using an inbuilt heat exchange panel for the duration of the trial.…”