The Science of Size Limits
Regulations Are Protecting Abalone
Red abalone.
Credit: Dave Rudie California Department of Fish & Game's current legal size limit for
red abalones is optimal for protecting the most reproductively important
adults, a new California Sea Grant study shows.
According to "matrix modeling" of red abalone reproduction, abalones
about 1 inch shorter than the legal size limit of 7 inches are the size
class with the greatest influence on population growth. The current
regulation, therefore, protects abalones that will most contribute to the
next generation.
"In our matrix models of red abalone populations, the size class with
the greatest influence on population growth was protected by the current
size limit," said lead investigator Laura Rogers-Bennett of the California
Department of Fish & Game, who received California Sea Grant funds to
conduct the study. "These results suggest the current size limit
regulation should stay where it is. It should not be shortened."
Rogers-Bennett and doctoral student Robert Leaf published their
findings in the journal Ecological Applications. In that same
paper, the authors suggested that, in light of the results, more should be
done to educate novice red abalone divers on how to reduce incidental
mortality of the critical sub-legal size class. They also suggested
tightening enforcement of existing abalone laws prohibiting high grading,
an illegal practice in which divers release small legal abalone for larger
ones they find later.
Recreational abalone diving is now strictly regulated in California.
Only one species is allowed to be fished, the red abalone, and only in
Northern California, seasonally, without SCUBA and only in daytime. There
is also a daily bag limit of three abalones, a yearly limit of 24, and as
already mentioned, only abalones 7 inches or longer can be taken.
The main problem is that abalones are easily injured in the process of
"popping" them from substrate, Rogers-Bennett said. Sub-legal abalones
that must be released and reattached to substrate have high mortality
rates.
This vulnerabilty stems from the fact that abalones have no
blood-clotting mechanism. They are effectively hemophiliacs and are prone
to lethal bleeding and/or deadly infections from seemingly minor injuries.
Divers should learn to eye the legal size before popping one, as the best
way to prevent harming reproductively important animals is to leave them
alone in the first place. "They also should never high grade, toss back
smaller abalone for larger ones they encounter," she said.
To increase public awareness about the issue, California Sea Grant is
collaborating with the California Department of Fish & Game to publish
an educational brochure for abalone divers, explaining basics of abalone
biology, how it relates to current red abalone regulations and diver
techniques for protecting important sub-legal adults.
In addition to performing analyses of red abalones, the scientists also
performed similar calculations for white abalones, which are federally
protected under the Endangered Species Act and subject to a recovery
effort. In the matrix models of white abalones, it was the largest size
class (between 5.5 inches and 6.9 inches) that was most important for
population growth. This length range constitutes the largest size class
for white abalone as white abalone are a smaller species than red abalone.
The authors say that their findings suggest white abalone restoration
efforts should focus on protecting adults not juveniles.
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