The effect of photoperiod manipulation on Atlantic salmon growth, smoltification and sexual maturation: A case study of a commercial RAS

Enrique Pino Martinez,Mitchell S Fleming,Pablo Balseiro,Cindy Pedrosa,Sigurd O Handeland,Tilde S Haugen

doi:10.1111/are.15107

Enrique Pino Martinez, Mitchell S Fleming + Show 4 more

Open Access

https://doi.org/10.1111/are.15107

Copy DOI

Abstract

The effect of photoperiod manipulation on growth, smoltification and maturation was assessed in Atlantic salmon through an observational study performed in a commercial RAS facility from June (25.0 ± 11.0 g) to October 2018 (151.1 ± 25.5 g). Half of the commercial cohort 721 was raised in continuous light LD24:0 (LL) while the other received a 6-week LD12:12 winter signal (WS) for smoltification from 12 August to 21 September. Parameters related to growth (body weight, gene expression of pituitary gh1 and gh2, and liver ghr1, igf1 and igfbp1a), smoltification (condition factor, plasma sodium and cortisol, gill NKA activity and nka1a, nka1b and nkcc1a expression) and maturation (GSI and pituitary fshb and lhb expression) were analysed. Afterwards, a multivariate analysis was performed on production data from five commercial cohorts raised in the facility (including 721) to identify variables potentially linked to early maturation in RAS. Results from the observational study indicated weak compensatory growth and slightly better smoltification in WS, although signs of size-induced smoltification were present in LL. Smoltification indicators were poor in both treatments, suggesting that smolts may not be yet ready for seawater. No maturation was observed in any photoperiod treatment; however, the multivariate assessment suggested that such lack of maturation might be rather linked to the low mean temperature and SGR experienced by our cohort.

Highlights

Salmon aquaculture is currently experiencing a shift towards intensification and the use of closed-containment systems (CCS), which allows more control over rearing conditions and may help solve sustainability issues associated with traditional salmon farming (Good & Davidson, 2016)
Recent communications from Bremnes Seashore AS (Norway) have reported percentages of early maturation ranging between 10% and 20% in some salmon groups raised in their new commercial Recirculation Aquaculture Systems (RAS) facility for postsmolt production at Trovåg, Norway (Knutsen, pers. comm., 2017)
Results from the basic multivariate assessment pointed at temperature as the variable most linked to early maturation, closely followed by growth

Summary

| INTRODUCTION

Salmon aquaculture is currently experiencing a shift towards intensification and the use of closed-containment systems (CCS), which allows more control over rearing conditions and may help solve sustainability issues associated with traditional salmon farming (Good & Davidson, 2016). The differences in photoperiodic conditions and timing of their introduction in these studies, they all found higher incidence of early maturation in groups of salmon exposed to winter light conditions followed by a switch to summer conditions Some of these studies (Berrill et al, 2003; Fjelldal et al, 2011, 2018) reported the occurrence of some mature fish that displayed certain morphological and physiological traits related to smoltification. In order to identify variables that might be most linked to early maturation during postsmolt production in RAS, we performed a basic multivariate assessment on production data from five commercial cohorts reared in the same RAS facility

| Ethic statement

| RESULTS

Findings

| DISCUSSION

| CONCLUSION