66 DECEMBER 2017 • WORLD AQUACULTURE • WWW.WAS.ORG physical and chemical treatments of fertilized eggs but triploid yields are variable (Allen 2011). Currently, triploid oysters of C. virginica are produced by crossing diploid females with tetraploid males, allowing greater efficiency of triploid production (Guo and Allen 1994). Modern biotechnology is becoming more accessible and is a valuable tool in genetic improvement of broodstock by pedigree analysis of DNA, gene mapping and the identification of genetic markers or specific genes associated with desirable traits. The application of such techniques have led to promising results in genetically modified individuals of surf clam Mulinia lateralis (Lu et al. 1996), black tiger shrimp P. monodon (Yazawa et al. 2005), and Pacific white shrimp L. vannamei (Sun et al. 2005). Overcoming Challenges and Knowledge Gaps Aquaculture of marine invertebrates has developed through investments in hatchery technology and broodstock management. Control of water quality and a basic understanding of the biology and ecology of cultured species favored captive breeding of many species. Although significant developments have been made, there are still several challenges in marine invertebrate broodstock management to achieve consistent production. Refinement of existing knowledge and management protocols are essential to maintain adequate conditions for gamete synthesis and spawning. Food quality and diseases are common to all cultures and represent major bottlenecks in broodstock management. Knowledge gaps remain about the exogenous and endogenous mechanisms controlling gametogenesis and spawning. How adults perceive and interpret changes in environmental factors is not fully understood. Research focusing on the endocrine system of invertebrates could shed light on the effects of environmental cues on gamete synthesis and spawning. As formulated diets become more popular, defining the appropriate levels of essential nutrients is fundamental to optimize gonad development and fecundity. Diseases are still the major cause of broodstock mortality and its management is paramount. Gaps in knowledge of the immune system of marine invertebrates restricts treatments. Mechanisms for rapid detection and control of pathogens are still under development and prevention of disease outbreak through biosecurity protocols is strongly suggested. Investments in breeding programs have resulted in great returns in the aquaculture of bivalves and investigations should continue for the selection of desirable traits in gastropods, crustaceans and echinoderms. Marine invertebrate broodstock management is a field of active study but challenges are multidisciplinary and integrated research approaches are needed. Notes Bruno L. Gianasi, Department of Ocean Sciences, Memorial University, St John’s, A1C 5S7, Newfoundland and Labrador, Canada. 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