Pacific salmon are Alaska’s most important renewable resource both for industry and identity. Economically, salmon account for 37% of the value of all seafood harvests. In 2003, the ex-vessel value for Alaskan salmon totaled $680 million (Warren 2014). Salmon are a crucial way of life for Alaskans, accounting for 60% of the commercial fishing jobs in the state as well as sport and personal use or subsistence fisheries. When you are at the supermarket, everyone knows that the most delectable and sought-after fish is the package labeled “Wild Alaskan Salmon”. All salmon landed in Alaska are wild caught, but what most people don’t know, about a third of the salmon were raised in salmon hatcheries before being released into the sea (Schultz 2013).
Alaska’s salmon hatcheries are often mistaken for other salmon aquaculture operations and their associated environmental and food safety concerns. Repeat after me, “salmon hatcheries are not fish farms, salmon hatcheries are not fish farms”. There are many important distinctions that you should be aware of between salmon hatcheries in Alaska and fish farms in Norway and Chile. First, salmon farming operations raise salmon their entire lives in captivity before being harvested and served for dinner. Unlike farming, all Alaska salmon are released into the Pacific Ocean and wild-caught. Fish farming is illegal in Alaska. You can think of hatcheries as salmon nurseries. Hatcheries rear salmon from eggs and raise them until they are ready to enter salt water (6 to 18 months). They are held for a few weeks in salt-water net pens (located in nearshore locations) before being released into the wild ocean as juveniles. These salmon will live unaided in the marine environment for 1-7 years, depending on the species and individual. Those that survive, generally 1-5%, eventually return to their release sites as spawning adults and are caught by fishermen. Hatcheries in Alaska are considered “fishery enhancement hatcheries” as their intent is to increase the number of salmon fisherman can catch. This differs from mitigation hatcheries that operate to compensate for the destruction of salmon spawning habitat. Of course, the salmon hatchery program in Alaska is not flawless. There are concerns about ocean carrying capacity and genetic effects from hatchery-origin salmon straying into stream with wild-origin salmon. However, thus far, hatcheries in the state of Alaska have operated alongside commercially viable wild salmon populations, parallel with their mission of “enhancement” of this magnificent natural resource.
During late spring here at Warm Springs Bay, you can see these little salmon adolescence schools around the new shore areas trying to put on some weight before they head out to the unknown sea. Walking on the dock, you look over the edge to see dense patches of skittish fish everywhere. In some places it seems there is more salmon than ocean. These little guys can cause quite the commotion here at the Springs. When there are this many fish congregated in one area they are sure to attract hungry predators. Leaning over to get a close look at the salmon and you are startled by a humpback whale blow right off the dock. You look over to see bubbles breaking at the surface, pectoral fins gliding along the bubbled path, and finally a huge baleen mouth lunging up and closing right before the giant submerges again below the water. I do believe Warm Springs Bay could be the only place in the world you can sit naked in a tube fed by natural warm springs, while watching humpback whales feed off the dock. Well, at least legally.
During the same time that the hatchery production was increasing during the 1980s, the humpback whale population was starting to recover from the industrial whaling days. Today, the whales wintering in Hawaii and returning to feed each year in the Gulf of Alaska are recovering at a rate of 5-7% per year (Barlow et al. 2011, Hendrix et al. 2012). The occurrence of humpback whales directly tagging released fish from hatcheries is a relatively recent phenomenon within the last decade. Since 2008, hatcheries have been reporting these baleen predators directly targeting released fish right off the docks and around net pens of the hatcheries. These whales are bold and intimate with the hatcheries. Some surface inside open net pens, while others just barely swim through tight spaces to reach dense patches of juvenile salmon. To address this new challenge, hatcheries have started experimenting with releasing larger fish, trickling fish out at a slower rate, changing the timing, and dragging net pens to different release areas. These strategies have shown a reduction in predation by humpback whales, but they can unintentionally increase predation from other predators such as sea birds, larger fish, and harbor seals.
Humpback whales are suspected of playing a role in some hatchery chum salmon run failures (the amount of adult salmon surviving to return to their release sites) in 2011 and again in 2015 [S. Reifenstuhl, Northern Southeast Regional Aquaculature Assocation (NSRAA), http://www.nsraa.org/?p=2088#comment-792]. Record low returns of chum salmon at hatchery release sites, Hidden Falls and Kasnyka Bay, resulted in an estimated 4-5 million dollar loss to southeast Alaska commercial fisheries (S. Reifenstuhl, pers. Comm.). In 2010, operations manager of the the Northern Southeast Regional Aquaculture Association (NSRAA) and University of Alaska, Southeast Professor and Whale Biology Jan Straley, collaborated to scientifically document this interaction for the first time. UAF, Ph.D. candidate Ellen Chenoweth developed the protocol that was supplied to five observation sights managed by 3 different organizations (Hidden Falls, Takatz, and Miss Cove-NSRAA, Little Port Walter-NOAA, and Port Armstrong-Armstron-Keta Inc.) on east Baranof Island. These observations have continued at all five facilities for five years (Straley 2010).
This is where I come in. My name is Madison Kosma. I am a first year graduate student with the University of Alaska Fairbanks, School of Fisheries. Since 2012, I have been working in Jan Straley’s Whale Lab and assisting in research on the Southeast Alaska humpback whale population. As a fresh graduate from the University of Hawaii, Manoa, I left the tropics behind and followed the whales to their northern feeding grounds. Being a research tech for Ellen Chenoweth and her initial work, humpback whale predation on hatchery salmon, lead to a thesis project and my application to graduate school. The last few years I have had the privilege of working with Jan Straley and Ellen Chenoweth. These experiences and opportunities have lead to my development of a solid foundation to launch my graduate work. Learning from these women has lead to some of the most valuable teaching moments of my career. From Ellen’s work with the hatcheries, a question emerged. How do we determine the contribution of hatchery salmon to the diet of humpback whales? This leads us into a whole other can of worms.
The feeding ecology of marine mammals is a very difficult thing to observe. Of course the first instinct to find out what an animal is eating is to look at stomach contents or, for lack of a better phrase, what it poops out. Two problems with this plan. First, you can’t look in a large marine mammal’s stomach without harming it and second, stomach content and poop analysis provides only a snapshot of the last few meals. As marine mammal biologists, we want to be the least invasive as possible to the animal and want the whole picture of the diet. Lucky for us, there is another way to observe diet. Bare with me, we are going to have a small little chemistry chat. All around us there are elements making up the world we live in. The atmosphere, the earth, the ocean, us, and the things we eat. The elements are made up of atoms. As you learned in grade school, atoms have electrons zoom around a nucleus that contains neutrons and protons. Let’s look at carbon. Carbon usually has 12 neutrons in the nucleus. The main tool my project will utilize is stable isotopes. Stable isotopes are atoms that have the same number of protons and electrons, but a different number of neutrons. In the chemistry world, this doesn’t change much BUT the carbon element with 13 neutrons (13C) is a little bit “heavier” than the carbon with 12 neutrons (12C). This means there are “heavier” and “lighter” carbons floating around out there in our world. Chemical reactions that happen around us prefer the “lighter” carbons. If you think of the reaction as a hill, it is harder for the “heavier” element to get up the “energy hill” of a reaction, so, more of the “lighter” carbons will make it to the top. This result of more carbon with 12 neutrons making it to the top compared to carbon with 13 neutrons is called fractionation. The ratio of the heavy and light isotope is the measurement we want and this is the measurement that varies in different parts of our world. Things in our world have “isotope fingerprints” that can essentially be used to identify them. After all of that is said, all you need to remember is; isotopic signatures in an animal’s tissues are similar to the signatures found in the foods they consume. So the diet of an individual can be determined by comparing the isotopic signature found in its tissues to signatures in possible prey species.
Have you ever heard, you are what you eat? Well, this is completely true. By taking a small clipping from your fingernail, I could find out if you are a vegetarian or meat eater and your consumption levels of corn products, processed foods, and sugar. This is done with just nitrogen and carbon stable isotopes. Stable nitrogen isotopes are fractionated as they move through the food web, with the ratio of the heavier stable isotope of nitrogen (15N) increasing relative to the lighter isotope (14N) with each tropic level (Vander Zanden and Rasmussen 1999). To estimate tropic level, the nitrogen stable isotope ratio value (d15N) can be used because the value of a consumer is typically enriched by 3-4‰, relative to its diet, as nitrogen moves through the food web (Post 2002). Each step of the food web has potential for fractionation and this leads to the top predator having the highest d15N (the greatest amount of heavy isotopes). Unlike nitrogen, carbon doesn’t change much as it moves through the food web; therefore, it can be used to evaluate the ultimate sources of carbon for an organism when the isotopic signatures of the sources differ (Post 2002). The stable isotope ratio of 13C/12C can be used to differentiate between diets based on plants with different photosynthetic pathways. C4 plants (e.g. wheat, rice, barley) have a distinctly different stable isotope signature than C3 plants (e.g. corn, sugar).
How does all of this relate to humpback whales and hatchery salmon? The key to my project is the fish feed that the hatcheries feed to their salmon. The carbon signature from the wheat in the fish feed give these little salmon a unique signature that differs from the humpback whale prey, that grow up out in the ocean. The fish food causes the hatchery salmon and anything that eats the hatchery salmon to shift their stable isotope carbon signatures more negative. Therefore, humpback whales that are eating hatchery salmon as a large part of their diet will be distinguishable from humpback whales not feeding on hatchery salmon. With the incorporation of a few other mathematical processes (I will not bore you with the contents of this today) we are optimistic that we will be able to determine the contribution of hatchery salmon to humpback whale diet here in southeast Alaska.
My proposed study directly addresses several issues regarding salmon fisheries and hatchery management in SE Alaska. First, hatcheries managers much decide how best to allocate resources and choose release tactics in order to maximize the number of adult salmon they produce for fisheries and the broodstock (returning adults for spawning) for the next generation. One product this research is an accounting of the actual effect that humpback whales have on productivity of hatchery releases. This knowledge will be an important source of information guiding the decisions of hatchery managers. Second, an adequate accounting of humpback whale predation on hatchery salmon releases will inform management of commercial fisheries as well. If humpback whale predation on hatchery salmon has a significant impact on hatchery productivity, increasing predation by whales could lead to hatchery salmon making up a smaller percentage of all Pacific salmon recruiting to commercial fisheries in SE Alaska. If managers do not adjust fishing efforts accordingly, this could lead to overfishing of wild populations (Naish et al. 2008). A better understanding of humpback predation on released juvenile salmon will help hatchery managers make informed decisions about release strategies, assist cooperative management of hatchery operations and release sites by the Alaska Department of Fish and Game and regional aquaculture associations, and maintain economically viable fishery yields for salmon fishermen. In turn, this will strengthen coastal communities’ dependent on fishery resources. Finally, our study will contribute to a broader understanding of change in SE Alaska coastal ecosystems, with implications for ecosystem-based management. As whales recover from the cessation of large-scale commercial whaling, their effects in marine ecosystems are expected to increase (Roman et al. 2014). Results of this study will contribute information necessary for the indirect effects of increasing humpback whale populations in the coastal waters of Southeast Alaska.
Fortunate for me, the Alaska Whale Foundation agreed to collaborate on this project. The state of Alaska is going through financial issues and with this comes education budget cuts. In times like this, organizations such as the Alaska Whale Foundation are crucial to the continuation of important research and the education of upcoming scientists. Having the use of the field station here at Warm Springs Bay, has proven to be vital to my project and the partnership with this fine organization is essential. Thanks to the support of the Alaska Whale Foundation director and board members, my graduate work and other research important to the state of Alaska, has the proper foundation for success. Funding for Alaska Whale Foundation’s research, education, and conservation programs comes from individual donors who share our passion for conservation. To help future graduate students, at a time when education is not properly funded, please consider donating today.