Deepwater chondrichthyans

The deep sea is a relatively stable environment, characterized by cold temperatures and poor or absent light. Relative to inshore shelf habitats, the ocean’s deepwater environments remain poorly known. The continued expansion of global fishing into the deep ocean has raised new concerns about the ability of deepwater organisms to sustain the pressures of exploitation (Morato et al. 2006). General knowledge on the deep sea lags behind the expansion of fisheries (Haedrich, Merrett, and O’Dea 2001) and as such management is often further behind. The intrinsic vulnerability of the chondrichthyan fishes given their life history characteristics (Hoenig and Gruber 1990; Cahmi et al. 1998; Musick 1999) is widely acknowledged and often cited. This vulnerability may be heightened in the deep sea, where conditions result in slower growth rates and reduced recruitment to populations. The vast majority of available life history data on the sharks, batoids, and chimaeras comes from the shallow water. Logistical, biological, and geographical difficulties with sampling (i.e., scattered distributions, deep occurrence, taxonomic uncertainty, and limited material) in the deep sea have limited the present state of knowledge. The amount of available information has, however, increased in recent years, and demonstrates that deepwater species are among the most unproductive of the chondrichthyans.