No abstract

Concern about the overexploitation of wild aquatic resources, the slow recovery of the groundfish fisheries and the need to encourage the diversification of the mariculture industry of the province of Quebec (Canada) all provided strong incentive to explore the potential of a wide selection of marine and anadromous fish species for cold‐water mariculture. Starting from a list of over 45 indigenous fish species of potential commercial interest, a biotechnical review was initiated. Technical sheets for each species were produced and aquaculture‐based selection criteria covering three aquaculture approaches of development (complete life cycle, on‐growing and stock enhancement) were examined. Species were ranked according to their degree of suitability for the given biological parameters. The final classification analysis within the complete life cycle production strategy positioned the Atlantic wolffish as the top candidate species (91%) followed by the spotted wolffish and Arctic charr (87%). Growth rate, optimal growth temperature, duration of the weaning period, minimal lethal temperature, larval size and feed requirements were the determining criteria. The on‐growing scenario final results ranked Arctic charr first (84%) followed by Atlantic cod (79%) and Atlantic halibut (74%) mostly owing to their growth rate at low temperature and optimal growth temperature criteria. Stock enhancement programmes should concentrate their efforts on the striped bass (56%), the haddock (54%) and the Atlantic sturgeon (34%) based on their growth rate, fishery status, landing price and the availability of impact studies.

The 'earthy' and 'muddy' o¡-£avours in pond-reared ¢sh are due to the presence of geosmin or 2-methylisoborneol in the £esh of the ¢sh. Similar o¡-£avours have been reported in ¢sh raised in recirculating aquaculture systems (RAS); however, little information is available regarding the cause of these o¡-£avours. Our hypothesis was that earthy and muddy o¡-£avour compounds, found previously in pondraised ¢sh, are also responsible for o¡-£avours in ¢sh raised in RAS. In this preliminary study, we examined water, bio¢lms in RAS and ¢llets from cultured arctic charr known to have o¡-£avours and requiring depuration using instrumental [solid-phase microextraction procedure and gas chromatograph-mass spectrometry (GC-MS)] and human sensory analyses. Geosmin was present in the samples taken from the bio¢lter and on the side walls of the tanks. Twomethylisoborneol was only found in low levels in the samples. The GC-MS results indicated the presence of geosmin in the ¢llets (705 ng kg À 1 ), but lower levels were found in the water (30.5 ng L À 1 ). Sensory analyses also detected an earthy £avour (i.e., geosmin presence) in the ¢llets, and, therefore, it appears that geosmin is the main compound responsible for the o¡-£avour in RAS. Further studies are being performed to identify the microorganisms responsible for geosmin production in RAS.

Environmental conditions such as temperature and water velocity may induce changes among alternative developmental pathways, i.e. phenotypic responses, in vertebrates. However, the extent to which the environment induces developmental plasticity and integrated developmental responses during early ontogeny of fishes remains poorly documented. We analyzed the responses of newly hatched Arctic charr (Salvelinus alpinus) to four experimental water velocities during 100 days of development. To our knowledge, this work is the first to analyze developmental plasticity responses of body morphology to an experimental gradient of water velocities during early ontogeny of fish. Arctic charr body size and shape responses show first, that morphometric traits display significant differences between low and high water velocities, thus revealing directional changes in body traits. Secondly, trait variation allows the recognition of critical ontogenetic periods that are most responsive to environmental constraints (40-70 and 80-90 days) and exhibit different levels of developmental plasticity. This is supported by the observation of asynchronous timing of variation peaks among treatments. Third, morphological interaction of traits is developmentally plastic and time-dependent. We suggest that developmental responses of traits plasticity and interaction at critical ontogenetic periods are congruent with specific environmental conditions to maintain the functional integrity of the organism.