Historical ecology and the conservation of large, hermaphroditic fishes in Pacific Coast kelp forest ecosystems.
The intensive commercial exploitation of California sheephead (Semicossyphus pulcher) has become a complex, multimillion-dollar industry. The fishery is of concern because of high harvest levels and potential indirect impacts of sheephead removals on the structure and function of kelp forest ecosystems. California sheephead are protogynous hermaphrodites that, as predators of sea urchins and other invertebrates, are critical components of kelp forest ecosystems in the northeast Pacific. Overfishing can trigger trophic cascades and widespread ecological dysfunction when other urchin predators are also lost from the system. Little is known about the ecology and abundance of sheephead before commercial exploitation. Lack of a historical perspective creates a gap for evaluating fisheries management measures and marine reserves that seek to rebuild sheephead populations to historical baseline conditions. We use population abundance and size structure data from the zooarchaeological record, in concert with isotopic data, to evaluate the long-term health and viability of sheephead fisheries in southern California. Our results indicate that the importance of sheephead to the diet of native Chumash people varied spatially across the Channel Islands, reflecting modern biogeographic patterns. Comparing ancient (~10,000 calibrated years before the present to 1825 CE) and modern samples, we observed variability and significant declines in the relative abundance of sheephead, reductions in size frequency distributions, and shifts in the dietary niche between ancient and modern collections. These results highlight how size-selective fishing can alter the ecological role of key predators and how zooarchaeological data can inform fisheries management by establishing historical baselines that aid future conservation.
Department of Anthropology, San Diego State University, San Diego, CA 92182-6040, USA.
Todd J
TJ
Braje
Program in Human Ecology and Archaeobiology, Department of Anthropology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, USA.
Torben C
TC
Rick
Department of Anthropology, Trent University, Peterborough, Ontario K9L 0G2, Canada.
Paul
P
Szpak
Department of Biology, University of New Mexico, Albuquerque, NM 87131-0001, USA.
Seth D
SD
Newsome
Department of Anthropology, San Diego State University, San Diego, CA 92182-6040, USA.
Joseph M
JM
McCain
Department of Biology, University of New Mexico, Albuquerque, NM 87131-0001, USA.
Emma A
EA
Elliott Smith
Department of Anthropology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
Michael
M
Glassow
Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA.
Scott L
SL
Hamilton
D000818:Animals; D002140:California; D003247:Conservation of Natural Resources; D017753:Ecosystem; D005398:Fisheries / Q000266:history; D005399:Fishes / Q000502:physiology*; D020387:Food Chain; D049673:History, 20th Century; D044423:Kelp / Q000502:physiology*; D010140:Pacific Ocean; D011157:Population Dynamics; D012617:Sea Urchins / Q000502:physiology
Channel Islands; Dietary Niche; Restoration Ecology; Zooarchaeology