The world’s oceans comprise our most extensive ecosystems. Yet they are the least well understood and so the conservation of marine biodiversity often lags behind that of terrestrial biodiversity. There is a relatively long history of marine resource conservation under international law and, presently, there is a considerable array of instruments aimed at the conservation of fisheries, both within national jurisdiction and on the high seas. Unfortunately many instruments still focus on exploitation, rather than conservation of both resources and habitats. Moreover they remain an incomplete response to problems of overfishing, illegal fishing and destructive fishing techniques. The result is a crisis in global fisheries. Whilst there has been considerable deliberation about the regulation of fisheries from a conservation and management perspective, attention to the impact of fishing activities on biodiversity is infrequent. In part this is due to the fact that many instruments were established prior to biodiversity emerging as a significant concern. However, it is now known that fishing activities constitute one the most significant adverse impacts on the marine environment. Although we might lament the absence of an obligation to conserve biodiversity from many fisheries instruments, the reality is that the conservation of biodiversity should be compatible the aim of sustainable fisheries. Of course there are some matters that need attention, such as the use of narrow stock based management measures and destructive fishing practices. Yet there are also matters of overlapping concern such as preventing overfishing and controlling illegal, unreported and unregulated fishing (IUU fishing). The aim of this chapter is to explore and explain the relationship between fisheries conservation and management and the conservation of marine biodiversity, to ascertain the threats to sustainable fisheries and the conservation of biodiversity, and to comment on the key strengths and weaknesses of the current law.