“How Fish Cope in a World of Feast and Famine”
Samantha Erickson I attended a seminar on “How Fish Cope in a World of Feast and Famine,” given by Dr. Johnny Armstrong. Dr. Armstrong received his doctorate in Ecology from the University of Wyoming with a emphasis in physiological ecology, specifically the adaptation and survival of fish. The study he explained in his seminar was completed in the Bristol Bay region of Alaska and studied Sockeye salmon. He talked about how he studied how the Sockeye ate in patterns where there were no food supply verses times where food supply was abundant. The object of his experiment was to watch the behavior patterns of the feeding of the fish at those different times and how the sockeye dealt with famine and with an overflow of food source. He set up areas in the middle of the streams where he could catch the fish at different times of feeding, or lack there of, and examine the contents of their stomachs. He found that in times where food was abundant, the Sockeye would stuff themselves to absolute breaking point with laid eggs. Then they would keep the eggs in their system by hardly swimming. Doing this they were actually able to not eat for three days in a row before having to eat again. In times where there was very little food, the fish would again use this method of hardly swimming, more just floating up stream to the warmer waters during the day, and travel downstream to cooler waters at night to scrape the bottom of the stream for whatever food they could find. I was curious as to whether the fish swam downstream to feed late at night to avoid predation or for another reason and presented the question to Dr. Armstrong during the seminar. Dr. Armstrong was unsure as to whether the fish choose late hours to swim downstream to feed in times of famine to avoid this predation but from what he hypothesized and what further research suggested, he does know that the migration between the warmer and colder streams is strategic due a conservation of metabolism (Armstrong, 2010). Dr. Armstrong was fascinated with his findings of how the fish are able to train their metabolism to keep the food in their system by gorging in times where there is more than enough and then using very little metabolic energy to conserve the food in times where there is very little. As far as the temperature of the streams contributing to the feeding of the Sockeye, Dr. Armstrong did not have time to go over in much detail but doing further research, I found that temperature is hypothesized to have more to do with feeding patterns than I originally thought after attending the seminar. The warmer water temperatures bring an increase in food and the fish are able to keep the food in their bodies longer in warmer streams because they have to use less energy, slowing down metabolism (Ruff et al 2011). I would like to do further research specially on how temperature effects this feeding pattern. If Dr. Armstrong were to watch the fish overnight or perhaps tag the fish I think he would be able to track their swimming patterns in given temperatures, when the Sockeye feed and if their feeding patterns are under a certain time every day or consistent with seasons and so on.
References
Armstrong, J.B. 2010. Comment on “Egg consumption in mature Pacific Salmon (Oncorhynchus spp.)”. Canadian Journal of Fisheries and Aquatic Sciences. 67: 2052-2054. abstract
Ruff, C.P., D.E. Schindler, J.B. Armstrong, K.T. Bentley, G.T. Brooks, G.W. Holtgrieve, M.T. McGlauflin, C.E. Torgersen, and J.E. Seeb. 2011 Temperature-associated population diversity in salmon confers benefits to mobile consumers. Ecology. 92: 2073-2084. abstract