Principal Investigator(s): David Berlinsky and George Nardi

I. Accomplishments

A. Scheduled Tasks
The objectives of these studies were to determine photo-thermal regimes conductive for stimulating reproductive development in winter and spring spawning Atlantic cod and to develop protocols for hormone-induced ovulation for manual spawning.

B. Progress on Tasks
We currently have independently-conditioned winter and spring spawning cod broodstock that volitional spawn sufficient fertilized eggs for 2 commercial production runs per year. Juveniles produced from such spawns are currently being grown in net pens in NH and Canada. Additionally, wild Atlantic cod broodstock from Massachusetts Bay were captured by otter trawl during their spawning aggregation (January) and transported to Great Bay Aquaculture where the ovulation induction experiments were conducted. Anesthetized fish (50 mg/l Tricaine-S) were uniquely tagged and gender and degree of oocyte development were determined by gonadal biopsy. Males were identified as spermiating or nonspermiating based on the release of milt when slight abdominal pressure was applied. To induce ovulation, females (n=4) in the late vitellogenic or final maturation stages were implanted with a 95% cholesterol: 5% cellulose pellet containing 200 µg [D-Ala6 Des-Gly10]-LHRH ethylamide (LHRHa) 7 days after capture. Control fish (n=3) received sham implants. To induce spermiation, 4 nonspermiating males were implanted with 200 µg LHRHa implants as above, and 4 fish received sham implants. Three days post implantation (dpi), and daily thereafter, female and male fish were examined for evidence of ovulation and spermiation, respectively, by exertion of slight abdominal pressure.

Three of 4 implanted females ovulated at total of 12 times (mean ovulation = 306 mls) and 1 sham-implanted fish ovulated once (300 mls). Spermiation was not induced in treatment or control fish. Ovulated eggs were fertilized with milt from non-experimental males to evaluate treatment effects on egg quality (fertilization and hatch). Buoyant (viable) eggs were separated from unviable (sinking) in a separatory funnel, and the embryonic cleavage was evaluated with a dissecting microscope at the 4-8 cell stage (n~200 eggs). Approximately 20 eggs from each ovulation were incubated in triplicate Petri dishes (~8 C, 10-13 days) to determine hatching success. The mean viable fraction of the ovulated eggs from the LHRHa ­implanted fish (52%) was significantly greater than that produced by the sham-implanted fish (25%). Similarly, fertilization and hatching success (41%, 3%) were significantly greater than those found in the sham-implanted fish (16%, 0%). These procedures were successfully used to spawn fish that were raised from eggs at GBA and brought to maturity on the NH-OOA net pens. This is the first report of a closed life cycle in Atlantic cod in North America.

C. Important Results or Findings
Manuscripts- “Hormonally-induced spawning of Atlantic cod”. Aquaculture Research. In preparation

Presentations- None

II. Tasks and activities for next reporting period
A. Tasks for the next reporting period
Conduct additional hormonally-induced spawning experiments on wild caught cod.

B. Brief work plan to accomplish tasks
Winter-spawning cod were recently captured from Ipswich Bay and brought to GBA, where they are being held in simulated ambient conditions. These fish will be treated with either LHRHa (injectable; 50 µg/kg or human chorionic gonadotropin (hCG; 330 IU/Kg). Possible benefits of these regimes include ease of preparation and FDA approval (hCG)

C. Anticipated concerns or difficulties
None.

III. Expenditures
All research goals will be accomplished within the designated budget.