Fish hatcheries have become ever more important in recent years due to the declines in wild stocks. The aim of hatcheries is to replenish the wild stock in order to keep the fishing industry sustainable, but there is still debate as to what is the best approach to this without causing further damage to the wild population. In an attempt to make improvements to hatchery practices, Hitoshi Araki studied the reproductive success of hatchery trout compared to wild trout, and made suggestions in his paper Hatchery Stocking for Restoring Wild Populations: A Genetic Evaluation of the reproductive Success of Hatchery Fish vs. Wild Fish (2008).
The hypothesis was that fish bred using the traditional hatchery methods, in which the fish are usually non-local and are bred for many generations in captivity, have much lower reproductive success than both supplemental hatchery fish and wild fish. The idea behind supplemental hatchery methods is to use local parent fish to breed “wild stock” hatchery fish in a protected environment, and then release them into the wild population, with the overall goal being to re-create a sustainable wild population. Using DNA analysis of steelhead trout from the Hood River, Araki determined the reproductive success of traditional hatchery fish, supplemental hatchery fish, and wild fish. He found that the more generations bred in a hatchery, the less reproductively successful the fish are.
Picture 1: Araki used his own data and data from previous studies to show the decline in relative reproductive success (RRS) as the number of generations in a hatchery increased.
Araki also found that supplemental hatchery fish had significantly higher reproductive success than the traditional hatchery fish, though they still had lower reproductive success than the wild population. When a wild stock parent was crossed with a traditional hatchery parent the reproductive success dropped. This shows the effect that hatchery fish can have on the wild population. If traditional hatchery fish continue to be released into wild populations in attempt to sustain them, they will continue to lower the reproductive success of the wild population.
It seems that, though hatcheries have a positive sustainability goal in mind, the traditional methods they are using to replenish wild stocks are somewhat counter-acting what they are trying to achieve. Though it may be more work to implement supplemental hatchery methods, the benefit of higher reproductive success of the population should be worth it.
Araki used steelhead trout as his example organism, but it is assumed that similar principles could apply to other fish species. In the San Juan and Vancouver Island area, salmon hatcheries are an important part of the fishing industry (and produce important food for the Southern resident orcas!). Since Chinook salmon are endangered in the area, a large amount of juveniles are released into the wild from hatcheries. From the information I could find, it seemed hatcheries in the area are attempting to use methods closer to supplemental techniques rather than the traditional methods. For example, the San Juan Enhancement Society in Port Renfrew, BC collect their broodstock (parent fish) of Chinook from a lake connecting to the San Juan River, therefore the juvenile fish are being released into their natural habitat. Though it isn’t stated how many generations are produced in the hatchery, it still could be considered a step in the right direction compared to using a non-local broodstock. Hopefully in the future hatcheries move towards supplemental practices so that the wild stocks, the ecosystem, and everyone utilising the fish can further benefit from sustainable fish populations.
Picture 2: Both wild and hatchery juvenile Chinook can be found in the San Juan Islands, as our Beam Reach class found out while beach seining on Lopez Island. The hatchery salmon had their fins clipped for identification.
Reid Harbor – Snug Harbor
After an efficent morning chore period, we had a long discussion of our current scientific methods and how they need to be changed and improved. Jason also began to examine the OrcaMaster data set.
In the afternoon, we sank a Vemco receiver in front of Val’s house to pick up the pings from the salmon experiments. The Vemco was deployed at 14:45 at 48, 33.7 and 123, 10.81 in around 10 meters of water. The serial number was 100913.
We did a quick drill with the hydrophone array and recorded the noise of the Gato Verde at 4 knots and varying speeds below as it slowed down. We did a quick man overboard drill with a hockey helmet that we’d found and then spent the early evening learning how to motor around in the dinghy. After a filling dinner, everybody worked through the evening. Peter and Val analysed some of the data we took on the Gato Verde’s noise levels and found some interesting results that will need further experimentation.
We’ve had a full, exciting day today, a perfect Beam Reach day. I woke a bit later than usual, rolling out of my sleeping bag at 7:50 and wandering into the kitchen to find that almost everyone had already eaten. Jason and Bubbles, his traveling sourdough starter, had made lovely sourdough pancakes.
Our morning meeting turned into an extended, incredibly helpful, strategy session. The conversation, led by Val and Jason, flowed smoothly and ranged from the last bits of research we need to complete for our proposals, to amendments to our data sheets and data collection systems to beginning to practice our analysis. I don’t know about the others but I ended up with two pages of notes and a long list of new things to address or research. About half way through, we decided to “make like plankton,” drifting from Stuart Island, south down Haro Strait, listening to various hydrophones all the while. We were so engaged that we almost, but only almost, worked past lunch.
Our morning meeting in the sunny cockpit
In the course of “making like plankton” we came across some interest flotsam. I asked for the definition of flotsam while writing this and Val promptly answered, “The things you find at garage sales.” It is actually, Todd tells me, the things you find floating in the water. Anyway, today we came across a hockey helmet, a construction hardhat and a circular piece of polystyrene (Styrofoam).
We had an equally busy afternoon, sinking a receiver in front of Val’s house to pick up the pings from transmitters put in salmon. Using an array (pun intended) of ropes, tapes, weights and boats, we managed to sink a cement block attached to the receiver and anchor it to land. As we left, we did a quick drill, pulling out the hydrophone array, as quickly and neatly as possible.
We were just beginning to relax again when Todd yelled, “Man overboard!” There was a great deal of running around without a clue where to turn, trying to decide who would keep their finger pointed at the “man” overboard. This was additionally confusing because for the first few seconds, none of us could see what was supposed to be the “man.” Hannah tossed the man overboard pole like a javelin and if it had actually been a person in the water, they probably would have been impaled. The hockey helmet, our “man” was successfully rescued and we proceeded into Mitchell Bay.
I had just gone to pull out my laptop and start work on the to-do list I generated this morning when Todd called us together and began dinghy training. Erica and I went first as the night’s cooks. It was like learning how to drive all over again only backwards, all with one hand and out in the wonderful, open blue.
The reason I wanted to blog about this day in particular was mainly an idea I had just before dinner while dicing garlic to fry with zucchini. It’s the “Man Overboard” thing. Not only did I feel like today was a bit of a continuous “Man Overboard” drill, in a good, thought-provoking, keep-you-on-your-toes kind of way, but I’ve sort of come to decide that all of Beam Reach is a bit like a “Man Overboard” drill.
It presents challenges that are usually unexpected, a bit nerve-wracking, and have an enormous payoff, if successful. All of our Beam Reach overboards seem daunting and confusing at first, but with helpful direction, good judgments, reliable instincts and hard work, we can complete the rescue successfully.
Today Val and Scott re-deployed a Vemco VR2 fish tag receiver at Lime Kiln State Park. This receiver, provided for this pilot study to Beam Reach by Fred Goetz, will help marine scientists understand how juvenile and adult salmon use the San Juans, in addition to any other passing fish that have been “tagged” (surgically-implanted) with 69 kHz acoustic tags. We at Beam Reach are most interested in the behavior and distribution of adult Chinook salmon, and secondarily any other potential prey of the endangered southern resident killer whales.
The photos above show the mooring prior to being snorkeled down to the pier block that remained from the previous deployment (last November).
Two other VR2s have been provided by Kurt Fresh of NOAA. (Their serial numbers are: 100910; 100913.) One will be deployed on the west side of San Juan Island; the other will be placed near Cattle Pass. We’ve mounted them on short (~2.25m) mooring lines (1.25cm diameter 3-strand poly), supported by single yellow shrimp pot floats (see below). The base of the receivers will be ~0.75-1m above the bottom. The floats will be ~1m above the top of the receivers. The mooring weights are either ~25kg concrete slabs (35cm x 35 cm x 15 cm; see below) or paint buckets filled with cement. Both types of weights have metal hoops or chain for attaching the mooring line and for lowering during deployments from a boat.
Data and analysis from these deployments will be documented in the Beam Reach science wiki
Last Sunday (11/09/2008), Jason Wood and Scott Veirs deployed a receiver that can detect and record the signals emitted by acoustic tags implanted surgically in migratory fish, like the Chinook and chum salmon that southern resident killer whales appear to prefer. The Vemco “VR2″ receiver, provided by Fred Goetz through a collaboration with UW Fisheries, was deployed during a scheduled maintenance dive on the hydrophones at the Lime Kiln lighthouse. The plan is to retrieve the VR2 in early 2009, download any serendipitous detections that may help in the interpretation of the echosounder data (to be presented at the Puget Sound Georgia Basin conference), and then redeploy it for the remainder of the winter (and perhaps the entire year).
The dive went well and lasted from about 11-12am. We enjoyed visibility of about 20m and pleasantly calm seas (it was very rough on Saturday when we initially planned to dive). We cleaned and secured the intertidal hydrophone and echosounder cable protectors, checked the VR2 mooring for buoyancy, and then followed the hydrophone cable to the two hydrophone stands (cement-filled paint-buckets with a broad tripod of embedded rebar). The VR2 was deployed 3m NW of the southern hydrophone and its mooring anchor was tethered to that hydrophone stand’s embedded chain and one of its rebar legs.
The VR2 mooring had a total height above bottom of 2m, with the receiver hydrophone oriented upwards about 1.4m above bottom. Since the mooring was deployed in 9m of water when the tidal height was ~2m, the depth of the receiver is about 6m below the tidal datum (0m). The mooring consists of a ~2m length of 1/2″ 3-strand polypropelene line connecting a ~3kg buoyancy crab float (used in lieu of an incompressible trawl float since minimal compression is expected at this depth), the VR2 (cabled-tied through and around the strands), and a stainless steel threaded shackle (bowlines at both ends). The shackle connects to a loop of 3/16″ plastic-coated wire rope that extends through a pier-block (via a 3/4 inch hole drilled through center line). The loop is secured with a clamp and is attached via sheet-bend to the ~4m-long tether (same type of line). All knots’ tails are secured with electrical tape. The float is marked with UW Fisheries research and Scott’s cell phone number.
Detailed photos of the mooring, including closeups of each component are available in the Beam Reach gallery.