By Lauren Frisch
University of Alaska Fairbanks researchers are using artificially fertilized sockeye salmon eggs to study the influence of water temperature on sockeye development.
Sockeye salmon are fished commercially all along the southern and western coasts of Alaska, and the largest sockeye harvest in the world is in Bristol Bay. This research will improve our understanding of how the species may respond to climate change, which has important implications for our understanding of this thriving fishery.
“Taking care of 50,000 babies is a lot of work,” said Morgan Sparks, a master’s student at the UAF School of Fisheries and Ocean Sciences. Sparks is responsible for sockeye salmon eggs that were fertilized at Lake Iliamna near Bristol Bay in summer 2015, and then raised at the UAF Biological Research and Diagnostics (BiRD) Facility.
Sparks is working with SFOS Assistant Professor Peter Westley and Jeff Falke, an assistant professor at the Institute of Arctic Biology Alaska Cooperative Fish and Wildlife Research Unit, to study the potential for Bristol Bay sockeye salmon to adapt to changes in water temperature by modifying hatch timing. The researchers at UAF are collaborating with the University of Washington Alaska Salmon Program, a research group with over 50 years of experience studying salmon in the Bristol Bay area. The project is funded by the Western Alaska Landscape Conservation Cooperative.
Westley anticipates this research will ultimately reveal that sockeye salmon have a high capacity to be resilient in the face of temperature change. He hypothesizes that the ability to modify hatch timing could allow sockeye salmon to successfully adapt to warming water temperatures.
“At the most basic level, hatch timing is dictated by temperature more than anything else,” Sparks said. Fish are cold-blooded, so their body temperature and metabolism depend on water temperature. When the water temperature is warmer, metabolism tends to be quicker, and vice versa. This could have important implications given expected changes in the region.
“Typically at colder temperatures, metabolism will be slower, and as a result growth rate will be slower and the fish will hatch later,” Sparks said.
Researchers have a limited understanding of how warming temperatures might affect sockeye salmon growth and development. “Being able to see adaptive response is important because it might indicate the ability of sockeyes to adapt to changing temperatures. We know there are going to be tremendous changes in Alaska and the Arctic, so I want to know how well prepared the sockeye salmon are to face those changes,” Sparks said.
Salmon lay their eggs in gravel beds called redds. When the eggs hatch, the tiny alevins can spend weeks or months in the gravel feeding off a yolk sac attached to their bodies. Since hatching is hidden in under the gravel, it is difficult to study in the field, so the researchers brought eggs back to the lab for their experiments.
Westley said it took a year to arrange logistics and get the permits needed for one long day in the field.
During their fieldwork, the researchers fertilized eggs from two populations in Lake Iliamna in the Kvichak River watershed. The populations were chosen because they represent different ends of the temperature spectrum in the lake, which could allow greater potential for different responses in developmental timing. One population spawns in the groundwater-fed Pedro Ponds just off Lake Iliamna, where water is typically cold and temperatures remain constant throughout egg development. The other population spawns on the shores of Woody Island in Lake Iliamna, where water temperatures are more variable over the course of development, starting out warm but gradually getting colder.
The researchers collected ten adult females and twenty males from each location, creating ten families of one female and two males for each population. Once fertilization was complete, the eggs were flown directly from Bristol Bay to Fairbanks in a chartered plane.
In the lab, Sparks is studying how embryos grow and hatch in temperature-controlled chambers replicating various temperature conditions for the two study sites. Two chambers are set up to replicate conditions at Pedro Ponds and Woody Island based on historical data. Two more chambers have warmer than average temperatures to reflect potential future conditions at the sites. Finally, one chamber replicates colder historical conditions from the Woody Island population. Eggs from each family were placed in each of the temperature-controlled chambers to control for genetic variability in each family.
Typically, studies comparable to this one have reared embryos at a constant temperature throughout the experiment. Sparks’ work is unique because he adjusts water temperatures daily to more closely match temperature fluctuations the fish might experience in the wild.
Sparks’ lab is immaculate. The BiRD facility conducts a variety of biological research, including research on wild animals, so the facility takes extra precautions to stay clean and safe for all workers and visitors. When I visit the lab in December 2015, Sparks takes me through three card-access doors and gives me a lab coat and shoe covers to keep my surroundings and myself clean.
The lab has two cool, dark rooms containing temperature-controlled chambers filled with developing salmon embryos. Sparks works there under a red light, which does not impact the developmental process. The lab has an additional room where Sparks weighs and measures the hatched fish.
During my visit, eggs in four of the five temperature chambers have hatched. Sparks visits the lab every day to check for hatched eggs and to measure the length and weight of all hatched alevins.
As you may expect with 50,000 babies, Sparks’ schedule is completely dependent on the hatch timing of the eggs. Sparks said the first two chambers hatched around the same time. With so many alevins to measure and store, he had a number of 14+ hour workdays. Although his workload has settled down since this initial hatching chaos, the eggs still drive his schedule.
The researchers anticipated that fish coming from families that spawned in water with variable temperatures would be more flexible to changes overall. But initial results show that average hatch timing for the Pedro Ponds population and the Woody Island population in each of the simulated environments is not substantially different. However, hatch timing varies for eggs among families within the two populations, suggesting the influence of genetics at the family level rather than the population level.
In short, the researchers are finding that hatch timing in their experiment has more to do with the embryo’s parents, rather than the population the egg came from. Sparks said this genetic differentiation is the kind of variability that natural selection can act on.
These preliminary results, suggesting that genetics is an important driver in dictating hatch timing for the fish, indicate that it will be important for sockeye populations to maintain this genetic diversity so they can adapt as water temperature changes.