CINEMar/Open Ocean Aquaculture Annual Progress Report for the period 1/01/04 through 12/31/04

Principal Investigator: Hunt Howell, Win Watson and Michael Chambers

I. Accomplishments

A. Scheduled Tasks

1. Grow cod, haddock and halibut juveniles to market size in offshore net pens.
2. Evaluate the growth performance and survival of cod, haddock and halibut in the project’s offshore net pens.
3. Evaluate the physiology and behavior of cod in offshore net pens.
4. Use behavioral and physiological data to improve the production of fish.
5. Collect data that will be used in economic analyses.
6. 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 to the UNH Coastal Marine Lab (CML) in New Castle, NH. At the CML, the fish were held in a flow through seawater system until October 2001. By October the halibut had reached 100g mean weight, and were transferred to one of our 600 m³ Sea Station cages. At this time, they were about 17 months old. 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. During their time in the cage, fish were fed either Shur Gain, Cory or Ziegler halibut diets, approximately daily, at a rate of 3-4% body weight. Monthly samples of the fish allowed us to track growth and survival. Growth in wet weight, and seawater temperature at the time of sampling, are shown in Figure 1. Temperature varied seasonally, from about 3-16° C. Because temperature was only measured periodically, colder or warmer temperatures may have occurred and gone unrecorded. Growth was steady throughout the 3-year experiment, although there was a tendency for growth rate to slow during the coldest months of each year. After one year in the cage, mean weight had increased to about 690g. By the end of the second year, mean weight was about 2200g, and fish were harvested at a mean weight of 2.9kg in May 2004, after 31 months in the cage. Fish were harvested by divers, brought to a surface vessel, bled, iced, and returned to shore in insulated containers. Approximately 1.5 tons were harvested. Specific growth rate (SGR) from this study were 0.6g/d for fish <500g, and 0.3g/d for fish > 500g. SGR for the entire period was 0.4g/d. Food conversion efficiency was 1.0.

Survival, from stocking to harvest, was 68%. Virtually all mortality occurred between May and August 2002, when logistical problems forced us to raise the cage to the surface. Although the halibut were still approximately 4-5m below the surface during this time, they were exposed to warm surface water temperatures (15-20° C) and bright sunlight. All fish that died exhibited lesions on the eyed-side consistent with fat cell necrosis (“sunburn”). A veterinary pathologist later confirmed fat cell necrosis as the cause of death, and mortality ceased when the cage was once again submerged to 15m.

Harvested fish were provided to a wholesaler, North Atlantic Seafoods in Portland, ME and a retail distributor, Seaport Fish in Rye, NH to assess their quality and marketability. A form describing the project, and requesting specific information, accompanied each group of fish. Information returned from each processor/distributor indicated the fish were of extremely high quality in taste and texture, and were therefore readily marketable.

2: Cod: Cod presently in the one cage were produced by Great Bay Aquaculture (GBA) early in 2003 using eggs and sperm collected from wild broodstock. 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 April 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 with 13,500 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. At the time of transfer, mean weight was 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 remaining 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 associated with the overnight on board the vessel and to 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 17, 2003, 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 (Figure 2). During the first year (September 2003 to 2004), the cod increased from 50 to about 400g mean weight. Since then, mean weight has increased to about 600g. Specific growth rate for their entire period offshore is 0.67 grams per day.

One of the major goals of the project was to develop a system that was capable of tracking the movements of free-swimming cod inside the net pen. During the winter of 2004 we purchased an HTI telemetry system and all the associated hardware and software necessary to run the system remotely. In addition, one of the graduate students associated with the project attended a workshop in Seattle to learn how to operate the HTI tracking system. In January and February we tested the system in the UNH pool and with cod that were located in pens attached to the docks at the Wentworth Marina. Once those tests were successful, we tagged some cod and released them in the offshore net pen and tracked them for periods of 2-6 hours. In this situation, the hydrophones were attached to the net pen and the cables were led up to the surface and connected to the receiver aboard a research vessel. This limited the period of time we could collect data, but it allowed for further troubleshooting of the system and collection of some very useful preliminary data. We presented some of this data at the World Aquaculture Meeting in Hawaii and it was well received.

During the spring and summer of 2004, we obtained some additional data for short periods of time and worked toward our goal of deploying the entire system within the feed buoy so that it would be possible to collect continuous data from tagged fish. When the feed buoy was moved closer to the submerged cage in August of 2004, we were able to successfully obtain tracking data for several days at a time.

As of November 29, 2004 we have obtained tracking data from a total of 20 fish. Of these, we have continuous data of at least 24 hours from 5 fish. Given that two reviewers suggested that our main goal should be to just demonstrate that it was possible to track fish in a net pen during the 2 year project, our success to date has been very gratifying.

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. Since then, their growth performance in the offshore cage has been good (Figure 3), 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), which should occur late next spring. 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.

Halibut: As outlined in last year’s report, we found that halibut were especially vulnerable to fat cell necrosis, which is a degeneration of the sub-dermal fat cells caused by excessive exposure to sunlight. 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.

Because of the many variables that effect growth, comparisons of the growth performance of the Atlantic halibut that we raised in a submerged, offshore cage, to halibut grown in land-based tanks or inshore net pens is difficult. SGRs from this study were 0.6g/d for fish <500g, and 0.3g/d for fish >500g. These are close to the maximal values reported for similarly sized halibut held in the laboratory. Our fish did not, however, grow at the rates suggested by Bromage et al. (2000), who reported that cultured halibut reach 2kg after1.5 yrs, and 3-5kg after 2-2.5 yrs. Our fish were smaller than this, having an average weight of about 1kg after 1.5 yrs, and 2.9kg after about 2.5 yrs in the cage. Although Bromage et al. (2000) did not report the culture systems or environmental parameters under which these growth rates were achieved, there may be several reasons for the slower growth we observed. The most likely is the cold ocean temperatures experienced by our fish when they were <500g. It has been reported by Bjornsson and Tryggvadottir (1996), based on constant temperature experiments, that the optimal temperature for 100-500g halibut is about 11° C. Temperatures experienced by our fish in this size range was <8° C. Although Bjornsson and Tryggvadottir (1996) did not report optimal temperatures for halibut in the 1-3kg size range, they did find that optimal temperatures decrease with increasing size, and that optimal temperature is 9-10° C for 3-5kg fish. Given this, we assume that fish in this intermediate size range (1-3kg) would do best at intermediate temperatures (approximately 10° C). Temperatures experienced by our fish during the months they were in this size range varied from about 3-11° C, with a mean of about 6° C. These cold temperatures may well account for the slower than expected growth we observed. Growth rates of halibut raised under ambient temperatures have also been reported. In western Norway, where ambient temperatures ranged from 4.5 ­ 12.5° C, fish grew from 1.8 to 4.1kg in one year (Rabben and Huse 1986), while in northern Norway, where ambient temperatures ranged from 0-13° C, fish grew from 1.6 to 3.7kg in one year (Haug et al 1989). In the last year of our experiment, mean weight increased from about 1 to 2.9 kg. Although our fish had a slightly smaller starting size than those reported by others, our observed increase of 1.9kg/yr, at temperatures ranging from 3-16° C, is comparable. Another factor that may have reduced growth was our inability to feed the fish each day. The culture site is located 10km offshore, and 2-3m waves are common during the winter and spring. Thus feeding only occurred on days that allowed the project vessel to safely attach to the feed hose.

As already indicated, there are a number of variables that effect halibut growth rate. It is unlikely that any of these influenced our observed growth rate as much as temperature. For example, stocking density was not a factor because we were well below the density (100% coverage of the bottom) that causes a decrease in growth rate (Bjornsson 1994). Similarly, the attainment of sexual maturity, which slows growth in both sexes (Bjornsson 1996), did not influence the growth rate of our fish because virtually of our fish were smaller than the size at maturity, and none displayed mature gonads when the fish were harvested.

It has been suggested that halibut are capable of achieving a 1:1 food conversion ratio (FCR) (Bromage et al. 2000). Experimental studies on the effect of temperature and fish size on feeding efficiencies (the inverse of FCR’s) have been done (Bjornsson and Tryggvadottir 1996). They showed that the highest feed efficiency for 100-500g halibut was about 0.4, and occurred at 10.7° C, while the highest efficiency for halibut 3-5kg was about 0.35, and was found at a lower temperature (5.5° C). Our calculated FCR (1.0) suggests that the diet we used was appropriate, and that halibut grown in submerged, offshore cages use their food very efficiently.

Results of this study indicate that halibut can be grown successfully in submerged, offshore cages. Although FCR was good, growth performance was lower than reported by others. We attribute this to suboptimal temperatures experienced by the fish in the submerged cage, and our inability to feed the fish on a daily basis. While temperatures could be increased at certain times of the year by bringing the cage to the surface, this would increase the risk of fat cell necrosis, and expose the fish to excessive temperatures during the summer months. Further, it would expose the fish to excessive current speeds and swells, that can cause loss of appetite, increased swimming activity, and even mortality (Martinez-Cordero et al. 1994). Although there are advantages and disadvantages of both submerged and surface cage culture, we believe it is advisable to sacrifice some growth in the colder, deeper water, in order to avoid the potentially lethal highly energetic, seasonally warm, and brightly sunlit surface waters. Automatic feeding systems, now being tested at our research site, should eliminate the problem of sporadic feeding, and thus improve halibut growth, even in offshore locations.

Cod: Cod are growing well, and there has been virtually no mortality. Examination of the telemetry data obtained so far has been very illuminating. While we are still processing the information, and no firm conclusions can be put forth until more data are available, it is possible to offer several observations: a. Fish do not appear to utilize the entire cage, at least within the time frame of 24 hours. Instead, they appear to spend most of their time around the outside edge, near the 25 m diameter rim. Typically, they do not swim around the cage in a circle, but confine their activity to one area. At some times of day they are very localized in one region of the pen. This contrasted diver observations of continuous swimming around the rim of the cage. b. The cod tend to be most active during the daylight hours. c. The fish appear to anticipate feeding and become more active in the hours prior to feeding. When food is administered they often rise toward the feeding tube to feed. However, they do not appear to rise to the feeding tube each time food is released during the 1 hour feeding period. Furthermore, some fish don’t appear to feed on some days. d. When tracking multiple fish, they do not appear to school, or move together. Rather, each fish appears to move independently of the others even though they may follow the same overall pattern.

Haddock: Haddock are growing well, and there has been virtually no mortality.

D. Difficulties Encountered
The only difficulty we have experienced with the haddock is high hepatosomatic indices (HSI). The relatively high mean value obtained in November 2004 (14.2%) was probably due to the relatively high lipid content of the diet. To counteract this problem, we will ask the feed manufacturer (Ziegler) to reduce the lipid content of the feed.

We encountered a number of challenges in the cod telemetry work during the initial year of the project. These included:

1. Deploying the system within the feed buoy.
Because the HTI receiver is connected directly to the hydrophones via long, expensive, cables we had to wait until the feed buoy was moved closer to the cod net pen in order to be able to lead the cables into the feed buoy and connect them to the receiver mounted in the buoy. Once the buoy was moved into place we were able to immediately get the system running as anticipated, and obtain continuous data.

2. Wireless communication
The HTI receiver and associated mini PC are located in a waterproof case inside the feed buoy. The easiest way to download data from the PC and make modifications of the recording parameters is to communicate with the PC using wireless technology. We are still in the process of optimizing this technology so that it works under field conditions.

3. Power
The HTI system and associated PC require a bit more 12 VDC power than we anticipated. While this problem has been solved, we have still encountered instances were the system has shut down in the middle of a recording session. This might be due to a number of factors, including power surges. We have attempted to fix this problem and program the software so that when it does shut down it will reboot successfully, so that we will not lose any data as a result of this type of problem.

4. Data analysis
When running properly and tracking 5-6 fish the HTI system generates thousands of data points each day (1 coordinate per fish every 2 seconds). One of our biggest hurdles has been figuring out ways to process and visualize these data. First, we were able to get a new program from HTI that aided in the very first step in the process, yielding accurate x,y,z coordinates for each fish without having to sort the data ourselves. Then we developed several excel macros to convert files into a format that was compatible with the Tecplot software that we use for visualizing the data. We also developed macros for calculating instantaneous swimming speed and the amount of time a fish spent in a given area of the net pen. Now that these software packages have all been developed it is much easier to obtain the type of information we seek from our large data files in a timely manner.

5. Broken cable
About a month after everything was deployed correctly and data collection was proceeding as planned one of the cables that runs between the HTI receiver and one of the hydrophones broke. This caused a considerable, unavoidable, delay, but this problem has been resolved and we are successfully collecting data again.

6. Respirometer
One of our goals is to measure the respiration rate of cod in the lab when they are forced to swim at different speeds in a respirometer. We designed and built a respirometer for this purpose during the first half of 2004, but then we had to focus on the work that was required for the tracking aspects of the project. We anticipate finishing construction of the respirometer and using it successfully during the winter of 2004-2005.

E. Anticipated Success in Meeting Project Objectives on Schedule
We anticipate meeting all the the project objectives. To date, we have grown high quality halibut to market size, and are successfully raising both cod and haddock in our offshore cages. We have monitored the growth performance and survival of all species at monthly intervals, we have been collecting data that will be useful in economic analyses, and we have been disseminating the results through scientific publications and presentations. We are very satisfied with the progress we have made with the cod telemetry work. We are collecting the type of data we had hoped to obtain and we are now fully capable of analyzing and visualizing those data so that we can use it to test our various hypotheses concerning the behavior and physiology of cod in offshore net pens.

F. Reports, manuscripts, and presentations resulting from the project
Presentations:
Chambers, M.D. and W.H. Howell. Open ocean, submerged culture of Atlantic halibut. 2nd Annual International Halibut Workshop, Halifax, Nova Scotia. January, 2004.

Howell, W.H. and M.D. Chambers. Recent advances in offshore cage culture of cod, Atlantic halibut, and haddock. World Aquaculture Society, Annual Mtg., Honolulu, HI. March, 2004.

Watson, W.H., C. Rillihan, W.H. Howell and M.D. Chambers. The use of biotelemetry to measure cod respiration and swimming activity in an offshore net pen. World Aquaculture Society, Annual Mtg., Honolulu, HI. March, 2004.

Howell, W.H. and M. D. Chambers. Cod and haddock production in submerged cages off the coast of New Hampshire, USA Gadoid Mariculture Conference, Bergen, Norway, June 2004.

Howell, W.H. Perspectives on cod, haddock and halibut culture at an offshore site. Aquaculture Assoc. of Canada, Annual Mtg., Quebec, Canada, October 2004.

Manuscripts Submitted:
Howell, W. H. and M. D. Chambers. In Review. Growth performance and survival of Atlantic halibut (Hippoglossus hippoglossus) grown in submerged net pens. Bull. Aqua. Assoc. Canada.

Chambers, M.D. and W.H. Howell. In Review. Cod and haddock production in submerged cages off the coast of New Hampshire, USA. ICES Journal of Marine Science

II. Tasks and Activities for Next Reporting period

A. Tasks for the next reporting period

1. Evaluate the growth performance, survival, reproductive biology and behavior of haddock and cod in the project’s offshore net pens.
2. Collect haddock and cod data that will be used in economic analyses.
3. Obtain sufficient telemetry data to write and submit a manuscript.
4. Use respirometer/swimming speed data to estimate the metabolism of fish in the cage.
5. Compare and combine real time video and fish tracking information to better understand cod behavior.
6. Disseminate results of the project.

B. Brief work plan to accomplish tasks
1. Haddock - Fish will be maintained 15m below surface, and fed by an automatic feed buoy 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.

2. 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. At the present time we have obtained sufficient data to provide insight into the behavior of cod in an offshore net pen. During the next couple of months we plan to double the amount of data we currently have and thus bring our number of trials to the point where we are confident in the trends we observe. We will use the data obtained to address the following hypotheses:
a. Cod are diurnal.
b. Cod do not feed at every opportunity.
c. Cod anticipate feeding times.
d. Cod confine their activity to certain areas of the net pen.

To estimate metabolism of cod within the cage, samples of fish will be placed in a respirometer and their oxygen consumption will be measured over a range of swimming speeds. The speeds chosen will encompass the range of speeds measured in fish in the net pens. From this data we will be able to determine the oxygen consumption of fish within the pens by converting their swimming speeds to the data obtained in the laboratory.

We will also examine the influence of changing temperatures on the metabolism of fish in the respirometer. One hypothesis concerning why cod restrict their activity to certain areas of the net pen is that they do not want to cross thermoclines that cause their metabolism to increase. Our laboratory studies will indicate whether simply changing the water temperature, either up or down, will cause a marked change in oxygen consumption.

A new underwater video camera system will be deployed in the cod cage in January 2005. The system will include 3, low light cameras that will be mounted in different locations around the cage. Camera placement will be near the rim, at the base of the spar facing up and near the feed pipe. The video imagery will be hard wired directly to the feed buoy where it will be processed through a multiplexer and recorded digitally. The goal then is to combine the digital video with the HTI data and Tecplot software to obtain a more complete picture of the activity levels and swimming patterns of the cod. In addition, real time video information will be transmitted back to a computer located at the Jere Chase Ocean Engineering lab. This will allow biologists to view fish behavior any time regardless of weather conditions offshore.

C. Anticipated concerns or difficulties
None.

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

Literature Cited
Bromage N, Mazorra C, Bruce M, Brown N, and Shields R. 2000. Halibut culture. In: Encyclopedia of Aquaculture (RR Stickney, ed.) pp.425-432, John Wiley and Sons, N.Y.

Bjornsson B. and Tryggvadottir SV. 1996. Effects of size on optimal temperature for growth and growth efficiency of immature Atlantic halibut (Hippoglossus hippoglossus L.). Aquaculture 142: 33-42.

Rabben H.and Huse I. 1986. Growth of juvenile (Hippoglossus hippoglossus L.) in captivity. ICES C.M. 1986/F:20.

Haug T, Huse I, Kjorsvik E and Rabben H. 1989. Observations on the growth of juvenile halibut (Hippoglossus hippoglossus L.) in captivity. Aquaculture 80: 79-86.

Bjornsson B. 1994. Effects of stocking density on growth rate of halibut (Hippoglossus hippoglossus L.) reared in large circular tanks for three years. Aquaculture 123: 259-270.

Bjornsson B. 1995. The growth pattern and sexual maturation of Atlantic halibut (Hippoglossus hippoglossus L.) reared in large tanks for 3 years. Aquaculture 138: 281-290.

Martinez-Cordero FJ, Beveridge M, Muir J, Mitchell D and Gillespie M. 1994. A note on the behaviour of adult Atlantic halibut (Hippoglossus hippoglossus L.) in cages. Aquacult. Fish. Manage. 25(5): 475-481.