commercial culture of
atlantic cod: addressing nitrogen, oxygen and total gas pressure during
larviculture
G.C. Nardi,
N.J. King
Abstract:
GreatBay Aquafarm (GBA), a commercial marine fish
hatchery and farm, produces summer flounder (Paralichthys dentatus)
and most recently black sea bass (Centropristis striata). As a
project participant in the UNH Open Ocean Aquaculture Project, GBA is
evaluating the potential for commercial production of Atlantic cod. Our goal
for this year is to produce enough juvenile cod to stock one of the
project’s offshore net pens. Broodstock codfish were spawned at the
NOAA-NMFS Narragansett, R.I. laboratory, and 397,000 eggs were transported
at 5 days post-fertilization (at 4°C) to the hatchery. Eggs hatched after
15 additional days of incubation (temp. 6-8°C), and 286,000 larvae were
stocked into four 4,000-l larval rearing tanks. Incoming culture seawater
(17°C) was degassed, injected with oxygen, chilled to 7°C, and allowed to
flow through the tanks. Larvae were fed a combination of rotifers enriched
separately with microalgae (C. Iso, or Tetraselmis), and
Algamac 2000® (Bio-Marine Aquafauna Inc.) for 20 days. Artemia
nauplii enriched with DC DHA Selco® (INVE Aquaculture) were fed to larvae
when they reached 8.0mm TL (16 dph), and weaning with microdiet Biokyowa
B400 was initiated at 15mm TL (~27 dph). Complications with swim bladder
inflation occur from 15-35 dph, and contributed to crop mortality.
Management of oxygen and nitrogen gas saturation, as well as the total gas
pressure of culture water, is essential in order to reduce mortality during
this critical stage. We will discuss the effects of supersaturation during
swim bladder inflation, and present growth and survival data from the
hatchery.
(GreatBay Aquafarms Inc., 153 Gosling Rd.,
Portsmouth, NH 030801, Canada)