Future Research Goals

Salish Sea

Chinook salmon migration patterns in the Salish Sea.

Chinook salmon migrate through the Salish Sea during the summer to return to their natal streams, including the Fraser River and Puget Sound stocks. Endangered southern resident killer whales (SRKW) prey consists of nearly exclusively Chinook salmon, and it is thought that their summer residency in the Salish Sea is correlated with prey availability. Unfortunately, current knowledge of chinook migration patterns is extrapolated from patterns of more abundant salmonids in the region, despite significant biological differences. Average swim speed and distance from the home river is used to calculate basin residency time, however given current research concerning migration around islands, and nuances concerning environmental conditions, these estimates may be widely inaccurate. A sound comprehension of basin residency time would allow further insight into the amount of available prey for SRKW over the migratory season. In addition, extensive research on the migration of juvenile salmonids has been accomplished, but adult migration patterns remain essentially unknown. Understanding the migration pattern of homing adult chinook salmon, including specific migratory routes, would give valuable insight into the foraging strategies and travel patterns of endangered southern resident killer whales, designate critical habitat for chinook salmon and aid in salmon management strategies.

The last study investigating migration patterns of chinook salmon in the Salish Sea was performed by Candy and Quinn in 1999. While this study was invaluable in understanding chinook habitat usage, its primary goals were to determine vertical distribution of Chinook salmon in Johnstone Strait. I would like to perform a similar study, focusing more strongly on residence time in the basin, horizontal migration routes and restricted to southern resident killer whale critical foraging habitat.

Role of competitors in southern resident killer whale nutrient stress.

The NOAA-DFO Workshop to Evaluate Effects of SalmonFisheries on Southern Resident Killer Whales identified competitors for chinook salmon as a primary area of concern in SRKW recovery.  Competitors for Chinook salmon in the Salish Sea consist primarily of harbor seals, California sea lions and Stellar sea lions, however, the role competitors play in restricting available prey for SRKW is remains unclear.  Marine mammal census in inland Washington can be extremely difficult and costly; annual census of harbor seals have not been conducted since the population reached carrying capacity, and the number of sea lions in the basin remain an assumed standard rate of dispersal from the primary population offshore.

Traditionally the impact of competitors has been determined using population abundances of the competing populations and target population, yet given the SRKW migratory patterns and lack of recent population estimates for competitors, using population abundance as a measure of competition can be unreliable.  Furthermore, determining causation rather than correlation can be extremely difficult using these methods, as numerous causes for decline may be responsible for reductions in population size.  The time-scale of population abundance requires all analysis to be on a macro-scale looking at annual variation while the impacts of competitors have more inter-annual factors.  Using physiological measures, such as nutrient hormones in SRKW scat, the impact of competitors on nutrient stress can give insight into micro effects of predators.   

To evaluate the impact of competitors on SRKW prey availability I would like to use several methods. To determine inter-annual effects of competitors I would like to use the nutrient hormones in fecal samples.  In addition, an increasing amount of energy is being invested in determining population abundances of marine mammals in the Salish Sea, including population estimates of porpoise, seals and sea lions.  Applying population abundances of competitors to SRKW population demographics will demonstrate whether competition is a cause for decline on an annual scale.  Lastly, I would like to construct a food-web model of the Salish Sea that focuses on factors contributing to primary prey abundance levels, and competitor prey source abundance levels as a method for evaluating causes of decline in SRKW.  

Resident abundance and migratory patterns of Dall’s porpoise in the Salish Sea.

John Shepard famously said “Counting fish is like counting trees, except they are invisible and they keep moving”. This sentiment is echoed in marine mammal population census, with a few key differences; marine mammals are only sometimes invisible and they often utilize sound. I developed an interest in population dynamics during my undergraduate studies, and found it most fascinating when the population of concern is difficult to quantify. Dall’s porpoise interest me due to their lack of notoriety despite a wide-range and remain abstruse despite being an integral part of the Salish Sea ecosystem.

NOAA acknowledges the existence of an inland Washington population of Dall’s porpoise, though due to a lack of recent population studies, their abundance is not included in overall West Coast abundance levels. The most recent Dall’s porpoise abundance survey occurred in 1995, identifying approximately 900 individuals.  Abundance surveys are difficult to perform aerially and on ship-based surveys due to diving bias and funding, as a result, information concerning the Dall’s porpoise in inland Washington waters is poorly understood, including a lack of research concerning distinct populations and residency patterns. NOAA assumes that populations will emerge based on genetic studies establishing distinct populations, yet such studies have yet to materialize.

Current abundance levels of harbor porpoise are being estimated by Pacific BioDiversity, utilizing acoustic measures.  Utilizing acoustic data to determine the presence of ceteacans helps reduce the cost of transect surveys and reduce the bias underestimating population sizes due to dive times. In a study by Kyhn et al (2013), Dall’s and habor porpoise in Canada were found to have consistently different audio signatures. I would like to do a similar study that measures Dall’s porpoise abundance and residency patterns using acoustic measures and visual methods.  Understanding Dall's porpoise abundance and residency will offer more information about the Salish Sea ecosystem, competition between threatened harbor porpoise and Dall's porpoise and implications for harbor and Dall's porpoise hybrids.  

Arctic

Arctic sea ice decline and shifting community structure of Arctic and Subarctic Cetaceans

There are three endemic Arctic cetaceans, bowhead whales, beluga and narwhal, however, as sea ice coverage declines, killer whales have been found to increasingly utilize Arctic habitat.  Killer whales are an apex predator that can have dramatic impacts on community structure when introduced.   Further exasperating this predatory relationship is the loss of sea ice that served as protection for vulnerable prey species, increasing the likelihood of deleterious effects on Arctic cetacean populations.  However, killer whales are not the only cetaceans capable of utilizing new Arctic habitat;  gray, humpback, fin and minke whales are currently Subarctic cetaceans expected to migrate farther north with declines in sea ice.  Understanding how Subarctic cetaceans are utilizing new Arctic habitat is paramount to understanding the changing Arctic ecosystem.  Whether the increase in Subarctic whales utilizing Arctic habitat will alter competition between endemic Arctic species, or offset the increased predation risk by northern killer whale migration is unknown. 

Using acoustic data, as well as satellite tags, if possible, I would like to investigate how a decrease in sea ice is changing subarctic mammal usage of Arctic habitat.  Specifically, I would like to utilize hydrophone arrays in Barrow, Alaska, and Hudson Bay to acoustically detect the presence of cetaceans, compared to annual and monthly sea-ice cover.  Using this data I hope to determine how community assemblage is changing in the Arctic.

Northwest Passage and its anthropogenic impacts on Arctic marine mammals.

The relative abundance of Arctic cetaceans are partly attributed to a lack of anthropogenic impact and pristine environment, compared to other pressures faced by cetaceans worldwide.  However, as the Northwest Passage becomes a reality due to loss of sea ice, anthropogenic effects may become a substantial factor in cetacean survival in the Arctic.  Declines in sea ice are expected to increase the presence of shipping vessels, opportunities for resource development as well as increases in human populations.  These anthropogenic effects have been found to have deleterious effects on cetaceans worldwide; having the opportunity to monitor anthropogenic effects on cetaceans from the beginning may give valuable insight into conservation in the Arctic, as well as worldwide.

In my current research,  I analyze how anthropogenic stressors impact endangered southern resident killer whales.  This research utilizes Automatic Identification Systems (AIS) required on all large vessels to track their presence in the Salish Sea.  Utilizing AIS in the Arctic could give great insight to increases in anthropogenic effects, particularly when paired with cetacean sightings and known vessel acoustic measures.  Ultimately, knowing the stress levels of these cetaceans would give larger insight to whether anthropogenic impacts are having deleterious results, though collecting fecal in the Arctic is quite difficult.  If it is opportunistically possible to collect fecal, or biopsies from Arctic cetaceans, analyzing the samples for stress correlated with sea ice reduction would be a valuable measurement of change in the Arctic.