Mariculture of the Oyster
Toadfish: Juvenile Growth and Survival
A.F. Mensinger, N.N. Price, H.E. Richmond, J.W.
Forsythe, R.T. Hanlon-2003
North American Journal of Aquaculture, 65(4):
289–299
Abstract:
Nests
of oyster toadfish Opsanus
tau with guardian males were transported from Waquoit Bay,
Massachusetts, to the Marine Biological Laboratory in Woods Hole,
Massachusetts. Following larval detachment from the nest, the offspring were
separated from the males and placed into culture tanks with flow-through
seawater. The juveniles were initially fed adult brine shrimp Artemia
spp. supplemented with small pieces of frozen squid Loligo
spp. During the second year of the study, the majority of the diet was squid
supplemented with locally available food. Fish were maintained at different
temperatures (approximately 15°C, 20°C, and ambient) and densities (2–90
fish/m2). Although the culture density did not have an
appreciable effect on growth, fish maintained in warmer water grew
significantly faster than fish kept at cooler temperatures. After 2 years,
the fish reared in warm water averaged 10.0 cm and 40.5 g, while those
reared in cold water averaged 6.5 cm and 11.0 g. Growth in weight was shown
to be exponential from day 76 to day 200, with rates of 1.4% and 0.38% body
weight per day at 20°C and 15°C, respectively, an almost fourfold
difference. Beyond day 200, growth in weight at both temperatures was best
fitted by a power function; however, there was no significant difference in
the slope of the growth curve between the two temperature groups. Thus,
temperature did not accelerate growth rates from day 225 onward. Survival
rates were greater than 68% in four of the five treatment groups. Despite
constant high temperatures and food availability throughout the winter
months, oyster toadfish underwent a quiescent period during the second year
of life and exhibited minimal growth during this time, indicating that
shortened day length may affect growth rates.
(Biology Department, University of Minnesota–Duluth, 10 University
Drive, Duluth, Minnesota 55812; and Marine Biological Laboratory, Woods
Hole, Massachusetts 02543, USA)