The Conservation Fund's Freshwater Institute (FI) has been culturing Atlantic salmon Salmo salar to market-size (> 4 kg) in a semi-commercial recirculation aquaculture system (RAS) for nearly a decade to assess the feasibility of this fish production method at relevant scale. During that period, FI has cultured salmon cohorts with various geneti cs and life history, sex distribution (mixed sex and all-female), and ploidy (diploid and triploid), from egg suppliers in North America and Europe. A wealth of fish performance data has been gleaned from these grow-out trials. Atlantic salmon typically grow to 4-5 kg in FI's semi-commercial scale RAS in 23-26 months post-hatch while maintaining feed conversion ratios of 1.1-1.3. However , most cohorts have demonstrated a propensity for early maturation under conditions common to FI's research facility (freshwater, 14-16 o C, hard water, around-the clock feeding, etc.) . Early maturation is generally undesirable to farmers , because fillet market-value is reduced due to pale flesh color, reduced product yield, and diminished lipid content. Thus , identification and genetic selection for strains that balance rapid growth with a reduced inclination for early maturatio n is a necessity for the growing land-based Atlantic salmon industry.
A recent grow-out trial evaluating all-female diploid and triploid Atlantic salmon from a European provider indicated further progress towards development of RAS-s uited stocks. G rowth performance of all-female diploid salmon was comparable to the fastest growing strains (North American) cultured onsite, and percent maturation for the all-female diploid and triploid groups was 13.6 and 0.0%, respectively. Overall, early maturation was substantially diminished in these cohorts compared to that of previous mixed sex populations (17 - > 50% maturity). A ll-female triploid salmon exhibited an increased prevalence of deformities, i.e. 16%, while no deformities were noted for sampled fish from the all-female diploid population. P ositive and negative characteristics for all-female diploid and triploid Atlantic salmon cohorts were realized, providing information t hat will guide RAS producers in weighing the risk/reward of these options.
A full summary of Atlantic salmon growth performance, maturation, and associated fish production conditions will be provided for cohorts produced at FI over the last ten years. Over all, FI's research has demonstrated that land-based production of market-size Atlantic salmon in RAS is both biologically and technologically feasible.