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Egg quality sablefish - Determination and practical application of egg quality measures
toward reliable culture of high-value marine finfish species
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There is increasing global awareness of the need for sustainable aquaculture. Aquaculture
represents a potential mechanism for supplementing wild fish harvests, either through
stocking of cultured animals or farming to market size. In the first case, stocked
animals would be available to sport and commercial fishermen. In the latter, consumer
demand would be met directly with a farmed product, reducing pressure on wild stocks.
By the year 2030, the global population is projected to reach 8.2 billion, with an
expected demand for seafood of 150 million metric tons (mmt), 54 mmt of which the
Food and Agriculture Organization (www.fao.org) estimates that aquaculture must contribute.
Meanwhile in the U.S., an astounding 86% of the seafood consumed is imported ($9 billion
annually), which makes seafood second only to oil as the largest natural resource
contributor to our national trade deficit. There remains a great need for U.S. aquaculture
production to fill the seafood void. Commercial-scale production of marine finfish
in the U.S. is limited to a handful of species, however, including red drum, Pacific
threadfin, cobia, cod, and flounder (excluding the anadromous Atlantic salmon), and
production is often inconsistent. On the U.S. West Coast, many native marine species
represent good potential candidates for aquaculture. Most of these, such as California
sheephead, California halibut, cabezon, lingcod, white seabass, and rockfishes, are
fully or over-exploited by capture fisheries. Other high-value species like California
yellowtail and yellowfin tuna are transitory, with apparently healthy populations,
but based on success elsewhere in the world, are believed to offer excellent potential
for commercial aquaculture development in the U.S. A major step in the creation of
a viable and profitable marine aquaculture industry lies in developing reliable fingerling
production, and central to this is understanding the variables that determine egg
and larval quality. The lack of knowledge in what optimizes egg and larval quality
is an important limiting factor in developing culture techniques for any species (Kjorsvik
et al. 1990; Bromage 1995). Inconsistent or poor egg quality significantly affects
the production and viability of larval and juvenile fish. In the absence of high-quality
eggs, it is not possible to optimize husbandry practices because larval performance
is substandard under typical culture conditions, such as high stocking densities,
aggressive weaning regimes, and grading or other handling procedures.
Unfortunately, identifying simple indicators of egg quality has been difficult as
no individual metric is universally applicable within and among species. This proposal
seeks to identify easy-to-use indictors, as well as determine pre- and post-spawning
factors that affect egg quality, in up to three very different ecologically and economically
valuable marine fish species native to the U.S. West Coast: a highly-pelagic finfish,
the California yellowtail (Seriola lalandi; CYT); a deep-sea whitefish, the sablefish
(Anoplopoma fimbria; SF); and/or a semi-resident benthic flatfish species, the California
halibut (Paralichthys californicus; CH). All three species are multiple batch spawners,
producing large numbers of eggs several times over the course of a spawning season.
Defining the differences between high and low quality eggs and documenting correlations
between quality and different conditions (e.g. broodstock diet, age, domestication
status, spawning methods, or progression through the spawning season) will directly
impact the success of culturing species like these. If inferior batches of eggs can
be identified early on, culturists would have a valuable tool, which would significantly
advance mariculture development along the U.S. West Coast and elsewhere by leading
toward consistent fingerling production of species with great potential for culture.
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