Masters Thesis

Evaluating the impact of a marine heatwave on the diet, growth, condition, and reproduction of California sheephead (Bodianus pulcher)

Marine heatwaves and other weather anomalies are growing stronger and more frequent, and yet the impacts of these events on marine organisms are not well understood in many cases. This study evaluated the potential impacts of a large marine heatwave on the diet, condition, growth, and reproduction of an abundant and important marine fish on rocky reefs and kelp forests off the coast of southern California. California sheephead (Bodianus pulcher) are among the most ecologically important fish on temperate reefs in California and Mexico, yet nothing is known about how warm-water events affect their diet, growth, or reproductive ecology. I quantified the diet, growth rate, body condition, and batch fecundity of California sheephead on three large rocky-reef kelp forests within the Southern California Bight from 2009 to 2020, a period which included a large marine heatwave from 2014-2016. Diet composition and prey availability were measured within a subset of this timeframe, from 2012 to 2018. Growth rates, reproductive output, body condition, diet, and prey availability all differed among the years, however, most interannual differences were not closely tied to the heatwave. Condition tended to be lower during the marine heatwave, but growth and reproductive output had no discernable relationship with the marine heatwave. Most measured variables differed considerably among the three large reefs studied, which were separated from one another by < 16 km, highlighting large spatial variation. Understanding the extent and causes of year-to-year and reef-to-reef variation in reproductive output and growth could aid in future management efforts of economically and ecologically important species of fish.

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