Table of Contents

• Cod and Haddock
• Black Bass
• References Used

Although the start date for the project was 10/01/99, funds were not received at URI until 8/18/00. Consequently, we initiated the project in the fall of 1999 but at a reduced rate of spending and activity. To accommodate the late arrival of funds for the project we have requested a no cost extension of one year to complete the studies outlined for the first year of the project.

Work in Rhode Island relevant to cod and haddock fell under two of the six objectives in the proposal:

1) Determine the suitability of cod and haddock for netpen culture.

3) Develop methods for disinfection of eggs of cod and haddock.

Under object 1 our commitment was to manage cod and haddock broodstocks and provide viable eggs to co-investigators for grow-out. Upon initiation of the project we had a well-established cod broodstock consisting of about 35 to 40 fish, some as large as 20 kg. The fish were held in the large 57-m3 oval tank at the Narragansett Laboratory. We put the tank on an advanced photoperiod schedule to initiate early spawning. By December the cod broodstock began producing large volumes of high quality eggs several times per week. Eggs were made available to co-investigators through March when production began to tail-off. We lost 80% of cod broodstock in July when the chillers failed and ambient water was added to the tank overnight, raising the water temperature to 18° C. The chillers have been repaired and arrangements made to acquire 30 cod from long-line fishermen out of Cape Cod, MA.

At initiation of the project, the haddock broodstock consisted of about 20 fish. We obtained 20 additional haddock from a long-line fisherman in December. Haddock were held in the 28-m3 rectangular tank at the Narragansett Laboratory and maintained on ambient photoperiod. The haddock began producing eggs in January. Eggs were made available to co-investigators through April when production began to tail-off. We routinely monitor egg production and egg diameter for both cod and haddock (Buckley et al. 2000).

An undergraduate student, under careful supervision, began work on objective 3 in February. Six experiments were completed with several disinfection treatments. Disinfection agents tested included: PVP-Iodine (WesternChemical), sodium hypochlorite (Clorox bleach), hydrogen peroxide (H₂O₂) and penicillin/streptomycin. Eggs were incubated after treatment in filtered seawater at 7° C and the percent hatch determined. The most consistent results with haddock eggs were observed in control groups where the mean hatch for the 6 experiments ranged from 44 to 63% (overall mean 50%). The penicillin/streptomycin treatment also produced consistent results with mean hatch rates ranging from 50 to 100% in the 6 experiments (overall mean 77%). The other treatment yielded more inconsistent results with mean values below that of the untreated controls. Mean hatch rates for PVP-iodine treated eggs ranged from 7 to 83%, while hatch of hydrogen peroxide treated eggs ranged from 13 to 94%. The inconsistent results between experiments with some of the treatments may have resulted in part from differences in the developmental state of the eggs at the time of treatment. These experiments will be resumed when eggs become available this winter.

The original project included three objectives to investigate the potential of netpen culture of black sea bass as listed below:

1) Determine the feasibility of culturing black sea bass to market size in netpens.

2) Ascertain the rearing densities and range of temperatures that provide for maximum growth of juvenile black sea bass.

3) Define the concentrations of environmental ammonia acceptable for survival and growth of juveniles.

Because of a reduction in the budget only one of the objectives was included in the final proposal. We have opted to focus efforts on two factors likely to promote significant gains in culture of juvenile black sea bass: rearing temperature and grading. To determine the rearing temperature that provides for maximum growth of sea bass and the profile of growth over a range of temperatures, juveniles will be reared at selected temperatures between 10 and 28^oC and growth rate determined. We have also observed a large range in the size of juveniles and resultant cannibalism. To investigate whether grading juveniles based on size will promote growth and reduce cannibalism, juveniles will be graded and the growth rate compared with individuals reared in ungraded tanks.

During the current reporting period efforts have focused on spawning adult black sea bass to generate sufficient juveniles to conduct the temperature and grading experiments. Some 36 females were strip spawned following induction of ovulation by implantation or injection of LHRHa. Juveniles resulting from these spawns currently are being cultured at URI and Great Bay Aquafarms and will be employed for grading and temperature studies to be initiated within the near future.

Buckley, L.J., T.M. Bradley, and J Allen (2000) Production, quality and low temperature incubation of eggs in Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus). J. World Aq. Soc. 31:22-29.