— Written by Ara Yazaryan
My experiment, now finalized, is very exciting: I get to study what the Sheephead of Anacapa are eating! My project is a quantitative assessment of Sheephead (Semicossyphus pulcher) stomach contents across several different sites and populations at Anacapa, part of the Channel Island chain. Anacapa has a unique conservation history, as the MPAs established here are of varying ages. One site is 40+ years old, and is one of the oldest Marine Protected Areas in the state of California. Another was established relatively recently, and the remaining areas of the island remain open for public use. Across these three study sites, I seek to determine the diets of Sheephead across different ages and areas.
First, Sheephead were collected from these three sites (with appropriate research licensing of course) via SCUBA spear-fisherman or – much to my angling delight – with hook-and-line. Next, the fish were dissected in lab. Various parts of the fish were saved for future study: the organs, otoliths, eyes, muscle tissue, gonads, and gills. But for my efforts, the stomach intestine was squeezed to release the slurry of partially digested fish food. These stomach contents were then weighed, placed into a Falcon Tube, and preserved in ethanol to prevent decomposition (and the horrendous smell that accompanies it). Upon preservation, I place these stomach contents into an examining tray to view under a dissecting microscope, under a snorkel vent to alleviate the less-than-stellar odour. Using a low-power scope to help me view the small pieces, I correspondingly separate the contents into categories. Based on my findings thus far, the majority of the sheephead gut contents consist of urchin spines and shell fragments, kelp encrusted in bryozoan colonies, small crabs, gastropods, and bivalves. However, a few unique finds have been unveiled: such as unidentified fish spines and scales (Sheephead
are not normally known to be piscivorous), octopi, pieces of gravel and sand, and even a plastic nurdle (a small bead of resin plastic such as polyethylene used in the production of larger plastic objects). Such variable stomach contents, once separated, will correspondingly be assessed to determine the composition by percent volume. Data will then be pooled from many fish from all three sites at Anacapa to determine dietary trends.
Though identifying, separating, and sorting each shell fragment may seem tedious at times, I am nonetheless driven by curiosity and the pursuit of scientific knowledge. Much like the Californian gold miners of old descending into deep, dark mines to unearth unknown treasures; I plunge my tweezers with nervous anticipation into the mushy lumps of partially digested Sheephead guts, facing constant perils and danger. Okay, maybe I am being a tad hyperbolic, but hopefully my point comes across. My stomach content examinations are part of a larger effort to understand fish populations, and the effects MPAs have on fish conservation. So I carry on with my unwavering efforts, to explore the vast unknown wilderness that is the world of fish guts!