ABSTRACT
Bluefin tuna is one of the most important species in the fisheries industry, caught in large numbers and highly priced in the market. There are three species of bluefin tuna, which are the Pacific bluefin tuna (Thunnus orientalis), Atlantic bluefin tuna (Thunnus thynnus) and southern bluefin tuna (Thunnus maccoyii). Although Pacific bluefin tuna was classified as a subspecies of Atlantic bluefin tuna until the late 1990s, it has been found to belong to the distinct species based on morphological observations and genetic studies (Collette 1999). During the past decade, exploitation of their natural stocks has increased to dangerous levels through the pressure of commercial fishing. It is therefore important to develop captive breeding and seed production techniques for this species in order to reduce the negative impacts of fisheries on wild tuna stocks. Recently, research advances have enabled successful broodstock development, and natural or artificial spawning of bluefin tuna (Kumai 1997; Sawada et al. 2005; Mylonas et al. 2007). Based on our understanding and the current state of development of induced reproduction in bluefin tuna species, natural and artificial spawning are not expected to be stable in terms of periodicity, batch fecundity, and egg quality. Thus, improving reproductive efficiency is crucial for artificial propagation and seed production techniques, and as such advances in research on the reproductive biology of bluefin tuna are critical. This chapter outlines some areas of research needing further clarification.
