CINEMar/Open Ocean Aquaculture Annual Progress Report for the period 1/01/03 through 12/31/03

Principal Investigator: Hunt Howell, Michael Chambers

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.

B. Progress on Tasks
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™ , Cory or Ziegler halibut diets), 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 (Figure 1 and Figure 2). Survival at this time is 68%. This is below what we anticipated, but the causes of the mortalities are well understood (see last year’s report), and have been corrected.

2: Cod
Cod production began at Great Bay Aquaculture (GBA) early in 2003 using eggs and sperm collected from wild broodstock. 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. All fish were dip vaccinated with Vibrogen 2, and repeated tests for the presence of Nodavirus were negative.

On Aril 23, 2003, a total of 30,000 cod (3g mean weight) were transferred to two 35m³ nursery pens near the Coastal Marine Lab in Newcastle, NH. These pens were constructed of 12.5mm stretch mesh, and covered to prevent bid predation. One pen was stocked with 16,500 fish and the second with13,500 fish. Fish in one nursery pen were fed a 1.8mm Ziegler diet at 4%BW/day, while those in the other were fed a 1.8mm DANA diet at 4%BW/day. Growth performance and survival of fish fed the two diets were compared for 6 weeks. At the conclusion of this experiment, both pens were fed the Zeigler diet. On April 29th, 3,000 more cod were added to pen B. Both pens were initially fed 3 times/day by hand, and later with an automatic feeder. As the fish grew, approximately half the fish from each pen were moved into two other pens to reduce stocking density. In July, warm water temperatures (>15°C) stressed the fish, and we began to see some mortalities caused by disease complications. Before water temperatures decreased and mortalities ceased, we lost approximately 8,000 fish. To offset this loss, GBA provided 6,000 more juveniles (25g mean weight) on August 8th, and an additional 5,000 juveniles on Sept. 12th.

On September 17, 2003, a total of 35,142 juveniles were moved offshore to a 200m³ nursery net (12.5mm stretch mesh) suspended within our 3000m3 Sea Station cage. Approximately 600 fish were left in the inshore net pen so that we can compare their growth and survival to those in the offshore cage. At the time of transfer, mean weight was about 50g. Transport of the fish was done by pumping the fish through a 30mm diameter hose into large tanks aboard a vessel hired for this purpose. On the first of two trips, with about half the fish onboard, sea conditions prevented us from transferring the fish into the sea cage. Because of this, they were held overnight in the vessel’s tanks, which were supplied with flowing seawater. The following day, we loaded the second half of the fish, and took them all offshore on the second trip. Transfer of the fish from the vessel to the cage, which was at the surface, was also done via fish pump. Following transfer, the cage was submerged to 10m. A total of 2,980 (8.5%) of the fish died over the next 10 days due to stress and mechanical injury associated with the transfer process. Fish have been fed commercial diets especially formulated for cod (Ziegler™ or Skretting™) since their transfer. On November 17th, fish in the offshore nursery net were released into the larger 3000m³ cage that surrounded it.

Growth and survival in the offshore cage has been good. Fish had increased to a mean weight of 77.5g in mid-November, compared to their approximate mean weight of 50g in mid-September when the fish were stocked. This increase of 27.5g was better than the performance of the fish left in the inshore cage, which had grown only about 5g during the same time period. The reason(s) for this are unclear, but we have seen some evidence of injuries to the inshore fish that we attribute to diving birds (e.g. cormorants), and it is possible that the fish have not grown well because they have been stressed by bird activity.

3. Haddock
As discussed in last year’s annual report, we began a program with haddock when the cod we were intending to use in 2002 were lost to Nodavirus. Our haddock work has been done in collaboration with Heritage Salmon Limited, New Brunswick, Canada, and the objective is to study the performance of haddock in offshore net pens. The project began in mid-September 2002, when a total of 3000 haddock (16 g mean weight), produced at the National Research Council Laboratory in Halifax, Nova Scotia, Canada, were transferred to UNH. They were placed in a 35m³ nursery pen located near the UNH Coastal Marine Laboratory, and fed a formulated diet (3-5 mm, DANA Feed) three times/day by a solar powered, automatic feeder. By mid-December 2002 their mean size had increased to 78g, and the fish were transferred to one of our offshore cages on December 18, 2002. Their growth performance in the offshore cage has been good (Figure 3 and Figure 4), and there has been virtually no mortality. Our intention is to leave the fish in the offshore cage until they reach market size (2-3kg). 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 halibut, haddock and cod suggest that all three species are excellent candidates for cold water, marine aquaculture. All seem to tolerate handling and transport very well, all seem resistant to disease, and all have shown very good growth performance when fed on a consistent basis.

As outlined in last year’s report we have found that halibut are 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 for halibut relates to fat cell necrosis, which is a degeneration of the sub-dermal fat cells caused by excessive exposure to sunlight. Our fish were held, for a few weeks in the summer of 2002, in a net pen just below the surface. During this time they rapidly developed lesions associated with fat cell necrosis. Although we lost several hundred fish as a result of this problem, most recovered when the net pen was once again submerged. Thus, an important finding is that halibut should be kept submerged well below the surface in summer months, or that surface cages should be provided with some shade cloth.

As regards cod, we have learned that birds can create problems for fish held in inshore net pens by inducing stress, and possibly by passing on diseases and parasites. Birds seem attracted to the pens because of the presence of the fish, and because the walkways are good roosting locations. We have developed some simple techniques that discourage the presence of some birds (e.g. herons and gulls), but diving birds (e.g. cormorants) continue to be a problem.

D. Difficulties Encountered
1. Halibut and Cod
Feeding at the remote, offshore location continues to be a problem. Because the halibut and cod net pens are not equipped with feed buoys, both species have been fed by hand since they were moved to the offshore cages. Feeding of the fish has been done by divers, or through the use of simple feed tubes that carries the feed to the submerged cages in a stream of water. Both methods require personnel at the site. Over the last year, the fish have been fed on each day that weather conditions allowed; 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 impossible to assess. A second problem with the cod was the mortality of some fish associated with transport from the inshore cage to the offshore cage. The use of a fish pump and transport vessel were chosen over previously used methods due to the large number of fish (>35,000) and their relatively large size (50g). It is likely that the mortalities occurred because of mechanical stresses associated the pumping operation, and because some of the fish remained in the vessel for about 24 hours. Despite these problems, there does not seem to be a viable alternative for moving relatively large numbers of fish.

3. Haddock
No significant difficulties have been encountered with the haddock. The only minor problem, also seen in cod, has been some mortality of the fish that are collected from the submerged cages and brought to the surface for growth measurements. As they ascend through 1.5 to 2 atmospheres of pressure their swimbladders expand, and approximately half of the fish die as a result of swimbladder rupture and/or internal injuries. We have experimented with bringing the fish up about half-way the day before we sample to facilitate some decompression, and also with releasing gas pressure from the bladder with a hypodermic needle. Neither has been effective, so the solution to this problem will require additional work.

E. Anticipated Success in Meeting Project Objectives on Schedule
We anticipate meeting all the the project objectives. We have grown halibut and haddock 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 have also stocked >35,000 cod in the largest of our cages, and to date they are growing and surviving very well.

F. Reports, manuscripts, and presentations resulting from the project
Chambers, M., H. Howell, C. Frantsi, N. Rennels and G. Rice. 2003. Cage culture of haddock, Melanogrammus aeglefinus, in the north Atlantic. World Aquaculture 2003, Salvadore, Brazil.

Howell, H. and C. Duffy. 2003. Investigating cod nursery stage rearing alternatives: comparison of sea-cage versus land-based. World Aquaculture 2003, Salvadore, Brazil.

Howell, H., M. Chambers, N. Rennels and G. Rice. 2003. Culture of Atlantic halibut, Hippoglossus hippoglossus, in offshore net pens. World Aquaculture 2003, Salvadore, Brazil.

Howell, H., M. Chambers and N. Rennels. 2003. Culture of Atlantic halibut (Hippoglossus hippglossus) in offshore net pens: an update. Flatfish Biology Conference. Westbrook, CT.

II. Tasks and Activities for Next Reporting period

A. Tasks for the next reporting period

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, halibut and cod in the project’s offshore net pens.
3. Collect haddock, halibut and cod data that will be used in economic analyses.
4. Disseminate results of the project.

B. Brief work plan to accomplish tasks
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 spring of 2003, when 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 will continue to monitor cod growth and survival in the coming year. We will be evaluating the physiology and behavior of cod using video and biotelemetry technologies, and using this information to improve production of the fish.

C. Anticipated concerns or difficulties
None.

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