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Egg Abundance and Spawning Biomass of the Hawaiian Anchovy or Nehu, Encrasicholinapurpurea, during 1984-1988 in Kaneohe Bay, Hawaii

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Title:Egg Abundance and Spawning Biomass of the Hawaiian Anchovy or Nehu, Encrasicholinapurpurea, during 1984-1988 in Kaneohe Bay, Hawaii
Authors:Clarke, Thomas A.
Date Issued:Jul 1992
Publisher:University of Hawai'i Press
Citation:Clarke TA. 1992. Egg abundance and spawning biomass of the Hawaiian anchovy or Nehu, Encrasicholinapurpurea, during 1984-1988 in Kaneohe Bay, Hawaii. Pac Sci 46(3): 325-343.
Abstract:In Kaneohe Bay, Hawaii, nehu (Hawaiian anchovy, Encrasicholina
purpurea) eggs were found primarily in areas where water depth was
> 10-12 m and were infrequently encountered near reefs, shorelines, or other
shallow areas. Eggs were usually most abundant near the centers of one or both
of the two large basins; the more enclosed southern basin usually accounted for
the majority of the total eggs present. Nehu eggs were present throughout the
year, but abundance was usually higher between July and February or March.
There was considerable shorter time-scale variation in egg abundance, but there
was no apparent underlying periodicity other than the annual cycle. Egg
abundance was poorly correlated with measured environmental factors; the only
potential relationship was that abundance tended to be low during the season
of strong northeast trade winds. Egg abundance in Kaneohe Bay was poorly
correlated with abundance in Pearl Harbor, Hawaii, the other major area where
nehu are found. Total numbers of eggs present in Kaneohe Bay reached about
109 during peaks. Based on available knowledge of nehu fecundity, spawning
frequency, and sex ratio, the biomass of spawning females was about 2 t and
that of all adults about 8 t during peaks of egg abundance. Catches of nehu by
the skipjack tuna baitfishery were poorly correlated with estimates of adult
standing crop, and most variation in catch was attributed to variation in effort.
Annual catches, however, were about five times the highest estimates of adult
biomass, and several monthly catches exceeded 8 t. The results indicate that
postmetamorphic nehu move into and out of and perhaps between spawning
and nursery areas such as Kaneohe Bay and that the total population is much
larger than that present in enclosed areas at any given time. Consequently,
further studies of the population dynamics of nehu and their interaction with
the fishery should be conducted on an island-wide and probably archipelagowide
Appears in Collections: Pacific Science Volume 46, Number 3, 1992

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