OOA Progress Report for the period 1/01/01 through 12/31/01

Principal Investigator: Hunt Howell and Michael Chambers, Univ. of New Hampshire

I. Accomplishments

A. Scheduled Tasks

1. Grow cod and halibut juveniles to market size in the project's offshore net pens.
2. Evaluate the growth performance, survival, reproductive biology and behavior of cod and halibut in the project's offshore net pens.
3. Collect data that will be used in economic analyses.
4. Disseminate results of the project.

1. Halibut: In May of 2001, 2000 juvenile halibut (30g mean weight) were purchased from R & R Development Ltd. in Digby, Nova Scotia. These were transferred, at a density of 22kg/m³, to the UNH Coastal Marine Lab (CML) in New Castle, NH. All fish survived the 17 hour trip. At the CML, the fish were held in a flow through seawater system, and fed 5% BW/day, until October 2001. During this time, stocking density increased from 4.7 to 12.7kg/m² as the fish grew. In October of 2001, when the halibut had reached 100g mean weight, they were transferred to one of our 600 m³ Sea Station cages. This was done in 1m³ insulated Xactics supplied with flowing seawater. Because of the relatively low number of fish, initial stocking density in the cage was 1kg/m². After the cage was stocked, it was submerged to 12m below the ocean surface. Since stocking, fish have been fed (Shur Gain™ halibut diet), approximately daily, at a rate of 3-4% body weight. Monthly samples of the fish have allowed us to track growth and survival. Growth in both length and weight have been good (Figures 1, 2 and 3). Survival at this time is 68%. This is below what we anticipated, but the causes of the mortalities are well understood (see section below), and have been corrected.
   
   
2. Cod: Cod production began at Great Bay Aquaculture (GBA) early in 2002 using embryos provided by the NOAA/NMFS Laboratory in Narragansett, R.I. Larval rearing techniques were changed to incorporate information learned over the last 2 years about water quality management, live food enrichment, causes of hyper-inflation of the swimbladder, and larval stocking density. Hatching success, larval growth and survival were remarkable. For example, growth rates of up to 5% per day were recorded, and survival was approximately 25% at day 100. A total of 200,000 three gram juveniles were produced. Unfortunately, the hatchery was struck by an outbreak of Nodavirus in June and July 2002, and all fish were lost (see later section for more details).
   
   
3. Haddock: The loss of the cod caused us to seek an alternative species for this year's trials. We were fortunate in being able to reach a collaborative research agreement with Heritage Salmon Limited, New Brunswick, Canada to do some joint research on haddock performance in offshore net pens. Juvenile haddock were being produced at the National Research Council Laboratory in Halifax, Nova Scotia, Canada, for Heritage Salmon. A total of 3000 of these (16 g mean weight) were transferred to UNH, and placed in a 35 m³ nursery pen located near the UNH Coastal Marine Laboratory in mid-September 2002. Here they were fed a formulated diet (3-5 mm, DANA Feed) three times/day by a solar powered, automatic feeder. As of mid-December, their mean size had increased to 78 g, and we have had very few mortalities. These fish were transferred to one of our offshore cages on December 18, 2002 (Figures 4, 5 and 6). We will monitor their growth performance and survival over the next year. This will be the first time that haddock have been raised in an exposed, offshore location. The haddock work is also gratifying in that we are working collaboratively with a large commercial aquaculture company.

C. Important Results or Findings
Results with both the halibut and haddock suggest that both are excellent candidates for cold water, marine aquaculture. Both species seem to tolerate handling and transport very well, both seem resistant to disease, and both have shown very good growth performance. One important finding is that halibut seem especially sensitive to the colonial hydroid Tubularia. It is one of the dominant members of the net pen biofouling community, and is characterized by having stinging nematocysts. Observations by our divers, as well as observed minor skin irritations on the ventral (non-ocular) side of the fish, indicate that halibut are sensitive to the stinging cells, and are reluctant to settle onto substrates populated by Tubularia. Halibut cages should be kept free of these organisms in order to reduce stress so the fish can achieve their maximum growth potential.

Another important finding related to fat cell necrosis (see later section), particularly the rapididity with which halibut began to suffer from it (a matter of weeks). We learned that halibut should be kept submerged well below the surface in summer months, or that surface cages should be provided with some shade cloth.

We also learned, along with many other researchers in Canada and Europe, that nodavirus is an especially virulent pathogen, and that it can cause catastrophic effects (see later section). As a result of this experience, we are now part of an international working group striving to understand the virus, trying to develop non-lethal diagnostic techniques, and working towards the development of a vaccine.

Finally, we learned that birds can create problems for fish in our inshore net pens by inducing stress, and possibly by passing on diseases and parasites. They seems attracted to the pens because of the presence of the fish, and because the walkways are good roosting locations. We have developed simple technques that discourage the presence of birds.

D. Difficulties Encountered

1. Halibut: Feeding at the remote, offshore location continues to be a problem. Neither of the feed buoys that have been developed have been reliable, and as a result, the halibut have been fed by hand since they were moved to the offshore cage. Feeding has been done by divers, or through the use of a simple feed tube that carries the feed to the submerged cage in a stream of water. Both methods require peronnel at the site. Over the last year, the fish have been fed on each day that weather conditions allowed feeding, and the fish have been fed an average of 3-4 times per week. The lack of any adequate means to feed the fish may have resulted in some reduction in growth, although this is impssible to assess.

   The experimental UNH feed buoy on the north cage was struck by a tug and barge in early May 2002, causing it to go adrift in the Gulf of Maine. Although the buoy was inoperable at the time, we decided to bring the submerged cage to the surface so the fish could be fed without the use of divers. In late May, we began transferring the fish (n=300) to the other cage, which was also located at the surface, but which was equipped with the MIT feeder. Following transfer of this small number of fish, we found that this feeder did not work, and all efforts to make it operable were unsuccessful. Thus the fish in both cages were at the surface, and were being fed by hand. The cage containing the 300 fish was extremely clean due to a recent application of anti-fouling paint. In mid-July, some of the fish in this cage died, displaying lesions on their dorsal surface. Samples were sent to our veterinary consultants, and the fish were diagnosed as having "sun burn"; more properly termed Fat Cell Necrosis Syndrome. The syndrome is a degeneration of the subdermal fat deposits, and is caused by a dietary problem (imbalance of oxidants and anti-oxidants) in combination with excessive sunlight. To alleviate this problem, we moved the surviving fish back to the more heavily biofouled, and thus more shaded, original cage. There were two other difficulties encountered. The first was abnormally high (>18°C) seawater temperature in July and August 2002, and the second was heavy biofouling by the colonial hydroid Tubularia sp. These two difficulties, which may have been related, caused the remaining mortalities. The fishes' aversion to settling on the Tubularia, presumably because of their stringing nematocysts, was evident to the divers, and it is likely that extended swimming, combined with warm temperatures, lethally stressed some small percentage of the fish.
   
   

2. Cod: Great Bay Aquaculture produced 200,000 juveniles (2-15g) in the spring of 2002. At 100 days-post-hatch (dph), there was no significant mortality among the fish. Shortly thereafter, the fish began to appear sick, and samples were sent to a veterinary diagnostician. By 115 dph, viral nervous necrosis (VNN), which is caused by Nodavirus, was detected using PCR techniques. At 120 dph, the mortality rate was 2% per day, and 50% of population showed clinical signs of VNN. PCR results were positive for all moribound and apparently healthy fish. Only 5 days later, at 125 dph, the mortality rate 10% per day, and about 50% of the population had already died. Again, PCR results were positive for both moribound and apparently healthy fish. The mortality rate increased to 20% per day by 130 dph, and fully 80% of population had died. Another 10% of the population died over the next 15 days, and all remaining fish in the hatchery were terminated. Thus in the course of just over one month, the population went from completely healthy, to completely descimated by VNN.

   In May 2002, at the beginning of the VNN episode, 10,000 (100dph ; 3g) cod were moved from GBA into one of our inshore net pens. All were apparently healthy, feeding well and showed no signs of VNN. Shortly thereafter, as water temperature approached, and then exceeded 12°C, the fish began to display VNN symptoms, and mortalites began. In the weeks that followed, the mortalities continued, and all fish began to show clinical signs of VNN. In August all survivors (about 300) were terminated because we did not want the disease to spread to any wild fish, and because we planned to bring the haddock (described above) to an adjacent location. The mean weight of the last surviving cod in August was 35g. At termination, a sample of 17 individuals were sent for PCR testing for VNN, and surprisingly, all were negative. This may suggest the survivors were disease resistance individuals who had not contracted the disease from others in the population, or that they had shed the virus.

   Because virtually all the cod died from VNN infection, and because there is some evidence for vertical transmission of VNN, we hypothesized that the NOAA/NMFS broodstock fish may have been the source of the disease. Working with Dr. Larry Buckley at the Narragansett Laboratory, 6 broodstock were sacrificed for testing, and 16% (1/6) were PCR positive for VNN. As a result of this testing, the cod broodstock at the NMFS Narragansett Laboratory was sacrificed. Efforts are currently underway to replace this broodstock.
   
   

3. Haddock: No significant difficulties have been encountered with the haddock. We had some minor problems with birds roosting on the inshore net pen floating walkways. Their presence may have stressed the fish, and their feces are a potential vector for diseases and parasites. We minimized the presence of birds by installing "bird scaring" devices, and because the fish are now in a submerged, offshore cage, there will be no further problem with birds.

E. Anticipated Success in Meeting Project Objectives
We anticipate meeting all the the project objectives for halibut. We have grown them in our offshore cages for over a year, we have monitored their growth performance and survival at monthly intervals, we have been collecting data that will be useful in economic analyses, and we have been disseminating the results through scientific presentations. We are quite pleased with their growth performance to date.

We will not be able to meet the project objectives for cod in this calendar year because of the difficulties described above. We intend, however, to complete all of these objectives in the near future. Cod production is scheduled to begin again at Great Bay Aquaculture in December, 2002. In this, they will use field stripped, wild fish, and both adults and samples of sperm and eggs will be tested for VNN. This testing, along with the installation of new equipment and improved health management practices, make it likely that hundreds of thousands of cod juveniles will be produced in 2003. We anticipate that some of these fish will be moved into our offshore system in the autumn of 2003, allowing us to complete the original project objectives.

In the interim, we have substituted haddock for the cod, and we will complete all of the objectives set out for cod using this species.

F. Reports, Manuscripts and Presentations
Howell, H. 2002. Culture of Atlantic halibut (Hippoglossus hippoglossus) in offshore net pens. Northeast Aquaculture Conference and Expo 2002. Warwick, RI.

Chambers, M., H. Howell and N. Rennels. 2002. Open ocean culture of Atlantic halibut (Hippoglossus hippoglossus) in New England. Aquaculture America 2002. San Diego, CA.

Howell, H. 2002. The UNH Open Ocean Aquaculture Program. New Hampshire Veterinary Association's Annual Mtg., Concord, NH.

Howell, H., M. Chambers and N. Rennels. 2002. Culture of Atlantic halibut (Hippoglossus hippglossus) in offshore net pens: an update. Flatfish Biology Conference. Westbrook, CT.

King, N.J. 2002. A case study of cod Nodavirus at GreatBay Aquaculture: Past outbreaks and plans for 2003. Nodavirus Workshop, Memorial University, St. Johns, Newfoundland.

II. Tasks and Activities for the Next Reporting Period

A. Tasks

1. Grow halibut to market size in the project's offshore net pens.
2. Evaluate the growth performance, survival, reproductive biology and behavior of haddock and halibut in the project's offshore net pens.
3. Collect halibut and haddock data that will be used in economic analyses.
4. Complete the work on cod.
5. Disseminate results of the project.

1. Halibut ­ Fish will be maintained in the cage in the coming year, and we will continue to monitor growth and survival. We anticipate that the fish will reach 2-3 kg by the autumn of 2003, at which time the fish will be harvested. One or more manuscripts describing the results of the project will be submitted for publication.
   
2. Haddock - Fish will be maintained 15 m below surface, and fed by an experimental feed buoy with a 5 mm extruded pellet diet. We anticipate that health management and feeding of the fish will be facilitated through the use of real time video telemetry from the fish cage back to the University. Sampling will occur every month for weight, total length and survival. Data collected from the study will be compared to those from fish grown in near shore cages at one of Heritage Aquaculture's sites in New Brunswick, Canada.
   
3. Cod ­ We anticipate that relatively large numbers of cod (tens of thousands) will be available in the coming year. Our plan is to transfer approximately 30,000 of these from the GBA hatchery to our inshore net pens. They will be maintained in this location until the autumn of 2003, and then transferred to an offshore cage. This should allow us to complete the tasks in the original proposal, i.e. grow the juveniles to market size in the project's offshore net pens, evaluate their growth performance, survival, reproductive biology and behavior, collect data that will be used in economic analyses, and disseminate results.

III. Expenditures

Expenditures were in the range anticipated for the work accomplished to date.