Crab hatchery technology update SHELLFISH CULTURE CRABS C. Brown, World Fisheries University, Busan, Korea J. He, Sun Yat Sen University, Guangzhou, China E. Quinitio, SEAFDEC, Iloilo, Philippines Spring 2018, Week 9
Crabs with some history of culture Mitten or hairy crabs (Eriocheir spp.) Mud crabs (Scylla spp.) Gazami crabs (Portunus triturberculatus) Blue swimmer crabs (Portunus pelagicus) Atlantic or Chesapeake Blue crabs (Callinectes sapidus) Long-term commitments lead to hatchery success
world crab aquaculture
Opportunistic scavengers Most are euryhaline, spawn in SW Opportunistic, tolerant of disrupted ecosystems Versatile scavengers - they eat almost anything Extremely fecund, 500,000 1,000,000 eggs/ Complex early life cycle, molted juveniles vulnerable High market value, nutritionally rich In most cases, farming initially depends on wild seedstock
Crab industry growth
Portunidae marine swimming crabs Most cultured crab species are Portunids These two spend the entire life cycle as ocean crabs: Gazami crabs (Portunus trituberculatus) Blue swimmer crab (Portunus pelagicus) Marine swimming crabs
Portunidae migrating swimming crabs These two live in coastal or brackish waters: Mud crabs (Scylla serrata, S. paramamosian, other S. spp.) migrate into fresh water Atlantic Blue Crab (Callinectes sapidus), another migratory Portunid crab
A burrowing crab: the Chinese mitten crab, or hairy crab, Eriochier sinensis Like prawns, they migrate into fresh water and return to the ocean to spawn
The biggest obstacle to mass crab culture
Chinese wild megalopae disappeared E. sinensis
Chinese wild megalopae disappeared E. sinensis
Hatchery production of large numbers of juveniles is challenging
E. sinensis culture after 40 yrs. research Mitten crabs survive well on simple diets Improved broodstock, larval nutrition Optimization of growth, synchronized molts
Broodstock nutrition
Larval nutrition Hatchery technology developing > 40 years Continuous long term commitment
Mitten crab farm earned GAA certification
Mud crabs FAO data sheets for 4 Scylla spp. Industry growth An artifact Aquaculture > capture
Soft-shell Scylla sp. production in Bangladesh
Bivalve broodstock diets in China
Expected mud crab progress in Vietnam
FAO Fact sheets 2 blue swimming crab species
Enhancement since 1963: up to 80% of wild catch originated in hatchery
Culture of Atlantic blue crabs Demonstration work ended in 2004
Atlantic Blue crabs near total collapse Up to 30 % of population is harvested annually Breeding stocks in decline Juvenile settlement rates alarmingly low Protective habitats (seagrasses, oyster reefs) lost Cannibalism accounts for up to 97% of juvenile diet
Maryland marine biotechnology ~8 yr. grant-funded hatchery & stock enhancement demonstration Larviculture work by Zohar et al. showed zoeae can be mass cultured megalopae become highly cannibalistic hatchery juveniles compete equally with wild, contribute to reproductive stock No commitment since 2008 to stock enhancement The practice is controversial, subject to politics Politics - antagonism between industry, government, science Hatcheries, enhancement viewed as unprofitable
2008 Zohar predicted release of 16M cultured blue crabs per year But FAO reports zero Atlantic blue crab aquaculture in the last 12 years