THE DEVELOPMENT OF HADDOCK CULTURE IN ATLANTIC CANADA
M.K. Litvak-1998
Bulletin of the Aquaculture Association of Canada, Edition 98-1: 30-33
Excerpts:
Canadian aquaculturists have long recognized the importance of diversification to stabilize the industry and provide opportunities for future growth. There are a number of species currently under research and development. Haddock, Melanogrammus aeglefinus, with its historical demand on the east coast of North America, is one of the most attractive candidates for culture in this region.
Eggs are disinfected with glutaraldehyde (400 ppm for 5 to 10 minutes) following a protocol developed for cod. Eggs are incubated in a variety of systems: static, recirculation, and flow through (upwelling and downwelling). Eggs have been reared in a variety of light regimes and although all conditions have resulted in larvae, there are no data on the effect of light on the viability of the larvae. Effects of photoperiod and light intensity on egg development are just now being studied by Gavin Downing, a PhD student at the University of New Brunswick in Saint John.
Depending on temperature, the 3 to 4 mm larvae will hatch in 2 to 3 weeks (5 to 8 C). Currently, larvae are reared in intensive land-based systems utilizing either flow-through or recirculation systems. Larval tanks are best stocked with eggs to minimize handling damage. Initially, stocking density was set at the standard cod model of 20 larvae/L. However, Linda Kling and her co-workers at the University of Maine, Orono, recently demonstrated that gaddids experience higher survival and growth when reared at very high densities (150 to 300 larvae/L). The attribute this response to the high clearance rates of live food (rotifers) placed in the tanks. The rotifers are typically enriched with Culture Selco (Artemia Systems NV, Belgium) and the quality of the rotifers decreases with time spent in the tanks. Therefore, high clearances rates ensure that the food ingested is of high quality and that there is little or no detrital build-up in the tank. Larvae are reared under continuous illumination at 250 to 1500 lux.
Currently, there is no artificial food that can be used to feed newly hatched haddock. The earliest time that larvae can be switched to an artificial diet and/or initiate co-feeding is still under investigation in a number of the laboratories. Thus, haddock, like many marine species being developed for aquaculture, depend on the production of live rotifers, Brachionus plicatilis. Fortunately, unlike many other species, haddock do not require algae for green-water culture or food. Larvae are often fed rotifers (10-20/mL, 2 to 3 times daily) until day 14 to 21 and are then co-fed Artemia (1 to 2/mL) and an artificial diet until metamorphosis. The production of rotifers requires space, supplies and highly qualified personnel trained in growing live feed. Unlike salmon hatcheries, a haddock hatchery must produce both fish and the food to feed them.
Alternatively, a lower intensity culture model could be used. Haddock larvae could be fed wild zooplankton, although the temporal variability in zooplankton abundance can make this a risky venture. Ken Waiwood successfully grew haddock larvae in large fabric mesocosms in the Biological Station's (Department of Fisheries and Oceans) tidal pool. These enclosures are a good prototype and his results indicate the potential for a large bag system to be used in lower intensity larviculture.
The weaning process has not yet been refined, and many larvae die during swimbladder inflation and at weaning. Larvae with hyperinflated swimbladders are often found struggling on the surface prior to death. Surviving larvae reach metamorphosis at approximately 25 mm standard length and after metamorphosis resemble the adult. Although there has recently been a quantum leap in production of juvenile haddock (particularly at Centre Marin in Shippegan), the optimal tank design, flow regime, and water quality parameters have not yet been clearly identified, and growth rates have not been analyzed.
(Department of Biology and the Centre for Coastal Studies and Aquaculture, University of New Brunswick, PO Box 5050, Saint John, NB, Canada E2L 4L5)