Experimental harvest of red sea urchins, Mesocentrotus franciscanus [A. Agassiz, 1863], and trends in red, green (Strongylocentrotus droebachiensis; [Des Moulins, 1837]) and purple (S. purpuratus; [Stimpson,... : Fs97-4/3244E-PDF

"In the early 1990s, a sea urchin research area was established near Tofino, BC, Canada, to conduct research on sea urchin populations. This report focuses on two studies between 1994 and 2012. The first study investigated the impacts of harvesting Red Sea Urchins (RSU; Mesocentrotus franciscanus) and the second study describes trends of RSU, Green Sea Urchin (GSU; Strongylocentrotus droebachiensis), and Purple Sea Urchin (PSU; S. purpuratus) populations over an eighteen year timespan. Experimental harvesting had minimal short (< 2 years) or long (5 year) term impacts on RSU. Within 2 years of harvest, significant decreases in mature and total RSU populations only occurred at a few sites. In contrast, immature RSU decreased significantly 5 years after harvesting at several sites, which may be associated with an El Niño event. Although variability was evident in all three species, populations remained relatively stable from 1994 through 2005 and then after 2005, urchin populations began to decline steadily until 2009 reaching near zero values of all indices until the end of the study period. The decline in sea urchin populations was likely associated with the establishment of a Sea Otter population near the research area in 2004"--Abstract, page x.

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