CINEMar/Open Ocean Aquaculture Annual Progress Report for the period 1/01/05 through 12/31/05
Principal Investigator: Hunt Howell, Win Watson, 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 initially held in the laboratory, and then transferred to one of our 600 m3 Sea Station cages when they reached 100g. Monthly samples of the fish allowed us to track growth and survival. Growth was steady throughout the 3-year experiment, and fish were harvested at a mean weight of 2.9kg in May 2004, after 31 months in the cage. Specific growth rate (SGR) for the entire period was 0.4g/d. Food conversion efficiency was 1.0. Survival, from stocking to harvest, was 68%. Full details of the halibut work are provided in the 2004 Annual Report, as well as in Howell and Chambers (2005). A second round of halibut culture is planned to start in early summer 2006.
2: Cod: The cod presently in one of the cages were produced by Great Bay Aquaculture (GBA) in 2003. In April of that year, a total of 30,000 cod (3g mean weight) were transferred to two nursery pens near the Coastal Marine Lab in Newcastle, NH. As the fish grew, approximately half the fish from each pen were moved into two other pens to reduce stocking density. In September 2003, the juveniles (mean weight 50g) were moved offshore to a 200m3 nursery net suspended within our 3000m3 Sea Station cage. Initially they were fed daily by the 1-ton feed and later by pump venturi from project vessels. A marine ration produced by Zeigler, 55% protein and 15% lipid, was administered daily. Feed amounts were calculated based upon fish size and temperature. Fishes’ activity levels were observed during feeding with low light, underwater video cameras mounted along the spar of the cage. Divers sample cod monthly using hand held nets and PVC framed dive bags. Growth in the offshore cage has been good (Figure 1). 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 1500g.
Harvesting: Some cod harvesting was done in 2005. Some of the fish were sold alive. Removing the live fish from the cage proved difficult because their gas bladders expanded as the fish were brought to the surface. To overcome this, techniques had to be developed to remove groups of cod from the SS 3000 cage, slowly decompress them, and then transfer the fish back to the live holding cages located near shore.
The live harvesting process began with a seine net being installed inside the cage to create a funneled capture area. At the end of the funnel was a 10” diameter hose that lead to hydraulic fish pump mounted outside the net and secured to the rim. A 10” diameter hose, 50’ long, connected the fish pump to an independently moored, subsurface harvest cage. The 280 m3, rectangular cage was suspended from a floating frame at the surface to a depth equal to that of the cage rim (25 m). Divers then herded the cod into the funnel where they were pushed toward the pump by means of a “crowder” (a triangular shaped, rigid net designed to fit the shape of the cage). Once transferred to the harvest cage the fish were then slowly brought to the surface from a depth of 70’ over a matter of hours following a strict decompression schedule. Once the fish reached the surface the fish pump was repositioned on deck and the fish were pumped out of the harvest cage and into 4 m3, live tanks on the service vessel. The fish were then returned to shore, and either placed in holding pens or put on the buyers truck after being dip netted out of the live tanks, counted and weighed. Mortality due to stress and decompression averaged 10%.
Live harvest proved feasible in the summer months due to long predictable bouts of calm weather, but as the weather worsened in the fall viable harvest days became increasingly scarce, and live harvesting ceased. The total live harvest was 1,145 fish, averaging about 1kg in weight. They were sold to Pacific Trade Inc. in Massachusetts.
Some harvesting of processed (bled and gutted) fresh fish also occurred in 2005. It was carried out in much the same was as the live harvest except that the cage was brought to the surface. The fish were herded down the “sock,” (the funnel shaped net) and pumped to a dewatering table on the deck of the service vessel, eventually ending up in a receiving bath. From there the fish were placed on a table where a small incision was made in the isthmus just under the operculum, and then immediately deposited into an ice slurry bath. This step cut one of the main arteries to the gills but did not kill the fish, thus allowing the fish to completely bleed out. From the bleed tank the fish went back onto the table where they were cut longitudinally and gutted before being returned to a seawater ice slurry bath. The fish were shipped to the buyers in this form. A total of 1,721 fish, averaging 1.2 kg, were harvested and sold to two different seafood buyers; North Coast in Massachusetts and North Atlantic in Maine.
Telemetry: 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 small cages attached to docks at the Wentworth Marina in New Castle, NH. 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 continuous 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. Unfortunately, in late December of 2004 the feed buoy that housed our instrumentation sank during a severe storm. As a result, most of our efforts in the last year have been focused on developing a new instrumentation buoy and testing it inshore. Our first task was to find a replacement buoy. The coast guard was generous enough to donate a surplus navigational buoy (Figure 2) that was retrofitted for our purposes. This buoy has two large waterproof tubes. One was used for batteries and the other for our instrumentation. We also added a “switch box” to the buoy to make it easier to connect all the input cables for our underwater cameras and other instrumentation. Finally, we also added two solar panels and a wind generator. A diagram of the new instrumentation buoy is shown in Figure 2, Figure 3 and Figure 4 contain block diagrams of the various components.
This new buoy has some of the features of the old system, as well as some new capabilities. The main feature of the buoy is an HTI Receiver and associated laptop computer to run the HTI software. Four 500 ft. cables connect the receiver to hydrophones attached to the outside of the net pen holding the cod. The length of the cables was increased so that we can deploy this buoy in the middle of the mooring grid, which will make it possible to collect data from any of the four net pens in the grid without having to move the buoy. The other major feature of the buoy is a new video system. This has three components. First, there are 3 underwater cameras located within the net pen and connected to the buoy via underwater video cables. There is also a surface camera to monitor sea conditions and potential disturbances. The output of all these cameras is recorded using a time lapse digital video recorder (DVR), capable of collecting weeks of data on a hard drive that can be swapped out each week. The video data is also going to be transmitted to a shore station and then made available in real time via the Internet. This updated video system will be an improvement over the last system. Another new feature of the buoy will be the capability to collect real-time environmental data from within the net pen. A current meter deployed within the net pen will be tethered to the laptop in the buoy and data will be stored every 5-30 minutes. This will make it possible to more accurately correlate fish movements with changes in tides and currents. The final new type of data collection consists of a hydrophone within the net pen that is connected to the DVR. This makes it possible to obtain audio recordings of the fish to supplement the video data. Several new studies have demonstrated the importance of acoustic signals in cod and these will be amongst the first recordings from fish in a semi-nature setting.
This new buoy is not large enough to house a generator. Therefore, we have chosen to power the system with 4-8 large 12V DC rechargeable batteries. These are connected to racks so that they can be easily added to, and removed from, the buoy. We expect each rack of 4 batteries will provide approximately 2-3 days worth of power for the instrumentation. The racks will then be removed, and replaced with fresh batteries, or else charged at sea if weather permits. Battery power will be supplemented with current produced by both the wind generator and solar panels. A low voltage cutoff system will prevent the batteries from being drained below 9 volts.
Currently we are testing the system inshore, using cod contained in a small cage located under the pier at the Coastal Marine Laboratory located in New Castle, NH. Most aspects of the system appear to be working as expected and the batteries are lasting at least as long as predicted. During the next few months we hope to collect all of the same type of data that we plan to obtain offshore, and test some of the same hypotheses. Thus, we will be well prepared to deploy a fully functional, well tested, system in the spring of 2006.
3. Haddock: As discussed in last year’s annual report, we have been studying the performance of haddock in offshore net pens. The work has been done in collaboration with Heritage Salmon Limited, New Brunswick, Canada. The project began in 2002, when a total of 2700 haddock (78 g mean weight) were transferred to one of our offshore cages. Their growth performance in the offshore cage was good (Figure 2). The loss in weight between February and July 2005 was associated with the fish spawning.
Haddock were harvested in September at approximately 1200g weight. Divers were used to herd the fish into a capture area similar to that explained in the cod harvest. Fish were transferred with an Aqua-Life model 1210-P fish pump onboard the service vessel. Haddock were passed through a de-watering table before being bled, gutted and placed into Xactics with ice slurry. A total of 2200 fish were harvested at termination. The remaining 500 were removed during the course of the project as samples for growth performance.
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 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 can be grown successfully in submerged, offshore cages. They are, however, 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. Halibut growth was good. 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. Specific Growth Rate (SGR) from this study was 0.6g/d for fish < 500g, and 0.3g/d for fish > 500g, and the Food Conversion Ratio (FCR) was 1.0. 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. The growth rates are close to the maximal values reported by others for similarly sized halibut. Although growth was good, we believe it could be improved if we were able to maintain the fish in optimal growing temperatures year-round by seasonally adjusting cage depth. Another factor that would improve growth is consistency in feeding. We anticipate that the addition of the new feed buoy will allow this to occur.
Cod: Cod have grown reasonably well. During the first year (September 2003 to 2004), the cod increased from 50 to about 400g mean weight, and since then, mean weight has increased to about 1500g. It is likely that growth has been hampered by two factors; both associated with the sinking of the feed buoy. First, we lost the ability to feed the fish regularly. Second, we lost the underwater lights that were in place to delay early maturation of the fish. As a result, many of the fish reached sexual maturity, and this decreased their growth rate.
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.
Flesh quality of the harvested cod has been variable. In some instances, the processors have reported “gaping” of the fillets (separation of the myotomes). The causes of this may relate to the method of processing and/or to the reproductive status of the fish when harvested. This is an important issue to resolve.
Haddock: Haddock grew well, there was virtually no mortality, and their flesh quality was good. The only difficulty we experienced with the haddock was their high hepatosomatic index (HSI). The relatively high mean value (14.2%) was probably due to the relatively high lipid content of the diet. To counteract this problem, we would recommend that the lipid content of the feed be reduced.
D. Difficulties Encountered
1. The major difficulty encountered was the loss of the feed buoy and its associated equipment. The loss affected the research in three ways: First, we lost the ability to feed the fish regularly, which undoubtedly led to some loss in growth performance. Second, we lost the HTI system, which prevented us from collecting the data needed for a major portion of the research. Third, we lost the underwater lights designed to prevent precocious sexual maturation of the fish. The ensuing early maturation probably led to a loss in growth performance, and may well have contributed to the suboptimal flesh quality of the harvested cod.
2. A second area where we experienced some difficulty was in the harvest of the cod. Live harvest was hampered by the pronounced thermocline (10oC between culture depth and surface) that exists during the summer months in the Gulf of Maine. We suspect that bringing the fish through this thermocline as they were raised to the surface caused some of the mortality associated with the early live harvests. Ideally, future live harvests should be carried out in either the spring or fall when there is a greater probability of calm weather combined with a thoroughly mixed water column. A second, but more minor, difficulty associated with the live harvest was our inability to harvest many fish during a single day due to the large volume of circulating water required to bring home relatively few fish.
3. A third difficulty was the unanticipated, suboptimal flesh quality of the cod. As indicated, this may have been due to the methods used in processing the fish and/or to the reproductive status of the fish when they were harvested. Information we have received from our Norwegian and Canadian colleagues indicates that cod-processing methodology varies within their countries. In general, however, the fish are starved for 1-2 weeks before slaughtering. At harvest, the fish are sedated using refrigerated seawater (RSW) chilling combined with the controlled addition of moderate levels of carbon dioxide. Fish are killed by exsanguinations (cutting of the gill arches), and then held in RSW for 30-60 minutes prior to gutting and washing. The final product is packed in ice. Both the Norwegians and Canadians suggest that flesh quality is improved with pre-rigor filleting. They also note that flesh quality is influenced by: a) stress levels during the slaughtering process; b) the type of feed; and c) the reproductive status of the fish, with poorer flesh quality associated with spawning fish.
E. Anticipated Success in Meeting Project Objectives on Schedule
We anticipate meeting all of the project objectives. To date, we have grown halibut, haddock and cod to market size 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 have also made good progress 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., W.H. Howell, C. Rillihan and W.H. Watson. 2005. Use of biotelemetry to optimize cod culture in submerged, offshore cages. European Aquaculture Society, Aug. 5-9, Trondheim, Norway.
Publications:
Howell, W.H. and M.D. Chambers (2005). Growth performance and survival of Atlantic halibut (Hippoglossus hippoglossus) grown in submerged net pens. Bull. Aqua. Assoc. Canada. 9: 35-37.
Chambers, M.D. and W.H.Howell (In Press). Preliminary information on 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
1. Continue to monitor the growth of the remaining cod.
2. Complete cod harvesting after the fish have spawned, which we anticipate will be in February 2006.
3. Cod transfer and culture. Great Bay Aquaculture has been contracted to produce 50,000 juvenile cod for a second growout trial. Cod are to be raised in a closed, recirculation system at their hatchery in Portsmouth, NH until they are approximately 75g. In the spring of 2006, they will be transferred offshore to a nursery net located inside the SS 3000 cage. A live haul truck will be utilized to transfer cod from GBA to the Port Authority in 5 m3 tanks supplied with oxygen. The tanks will be lifted with a crane and placed on the deck of a commercial fishing vessel and taken offshore. At the site, the vessel will moor next to the SS 3000 and deploy a transfer hose from the boat to the cage. Fish will be gravity fed into the nursery net within the main net. Cod will be observed by underwater cameras and fed daily. Initially, pellets will be fed via a boat mounted feed venturi and later by the newly deployed 20 ton feed buoy.
4. Halibut transfer and culture. A second round of halibut culture is planned for early summer 2006. Approximately 3500, 1 kg halibut will be stocked into the 600 m3 Sea Station cage to examine growout time to 5kg. The fish will be will transferred from Scotia Halibut in Clarks Harbor, Nova Scotia to the Port Authority in Portsmouth, NH in a smolt truck. From there, the 5m3 live haul tanks will be lifted with a crane and placed onto the deck of a contracted fishing vessel. Once the halibut are relocated offshore, they will be fed from the 20 ton feed buoy that will provide real time video transmission and controlled feeding. Divers will sample the fish monthly.
5. Deployment of the HTI fish tracking buoy. Previously the HTI fish tracking system was housed in the 1 ton feed buoy. With the loss of this platform, a retrofitted navigation buoy has been adapted to house the system. This retrofitted buoy will be deployed in the early spring 2006, and moored centrally above the grid so that video and hydrophone cables could be attached to any cage in the grid system. This system will be used until the new 20-ton feed buoy is deployed in the late spring. Once this occurs, the tracking system will be mounted inside the 20 ton feed buoy for greater access and stability. Cables for the system’s hydrophones, video, and current meter will be bundled in a protective hose and mounted in parallel with the feeding hose to the SS 3000.
6. Low volume fish cages for fishermen. The American Soybean Association (ASA) has been developing a small scale (100m3), semi-submersible fish cage for coastal China. UNH engineers have numerically modeled the system to evaluate dynamics within the water column. Discussions are under way to work with a local fisherman to demonstrate the use of this technology. The advantage of this system is that small cages could be readily serviced with existing gear on board area fishing boats.
III. Expenditures
Expenditures were in the range anticipated for the work accomplished to date.