Maintenance of Seamount Resources and Future Research Directions

Seamounts represent ocean features whose potential for biological resources has been largel) o\erlooked. The recent discover) of abundant fish resources in the southern Emperor Seamounts region, however, has led lo fisheries development and exploitation. We have little understanding of basic biological and population characteristics such as recruitment patterns, age distribution, the stock-recruit relationship, natural mortality, and trophic relationships among seamount species to form the basis for appropriate management. Seamount fisheriec differ in many respects from other fisheries so that innovative methods are needed to evaluate resource characteristics. Available information suggests that interaction of seamounts with ocean currents results in flow complexities including Taylor columns and eddies which may either increase productivity or aggregate prey organisms. Thus, seamounts may play important roles in the concentration of biological resources. Understanding the productivity and sustainability of these resources requires multidisciplinary approaches involving physical and biological oceanographic research. Seamounts are a dominant feature of the geomorphology of the Pacific Ocean, yet they have received relatively little study. Logistic constraints have generally limited biological investigations to smallscale efforts designed to consider the fauna present in particular locations (Pratt 1967; Raymore 1982). In the northern and central Pacific, however, the discovery of exploitable biological resources has intensified the study of the value and sustainability of seamount fishery resources in the Gulf of Alaska (Hughes 1981) and in the southern Emperor-northern Hawaiian Ridge (SE-NHR) region (Humphreys et al. 1984). Seamounts in the Gulf of Alaska have fish populations similar to those in coastal waters but unexpectedly high densities of several species of crabs (Hughes 1981), but no directed fishery has developed to exploit these resources. In the SE-NHR seamount group (Fig. 1) the development of a fishery preceded fisheries research. Since that time, new fisheries have developed, including those for bottom fishes besides pelagic armorhead, Pseudopentaceros wheelen' (Humphreys et ai. 1984), precious corals (Grigg 1982). albacore (Yasui 1986), skipjack tuna (Inoue 1983). and squid. Traditional fisheries research is difficult to conduct on seamounts. Seamounts are generally remote, making seasonal, repeated sampling difficult. Often, the fine-scale topography of the shallow portions of the seamounts is poorly known, although bathymetric studies continue (Smoot 1985). In the SE-NHR seamounts relatively little is known about the life history and ecology of the dominant species, their habitats, and the associated ecosystem; thus new approaches will be necessary to assess and determine the sustainability of the resource. Although limited in area, seamounts may serve as locations for concentration and transfer of energy from the pelagic to demersal ecosysiems. Demersal resources of seamounts may maintain high biomasses as a result of localized enhancement or concentration of the productivity of overlying waters. Our understanding of this productivity is largely at the hypothetical stage and few data exist. It is thus difficult to draw conclusions about possible mechanisms that maintain these large demersal populations. If productivity is indeed high, one can understand how large populations of fishes, deriving nutrition from overlying waters, could develop over time. A major concern, however, is the sustainability of these populations. On mid-Pacific seamounts, currently depressed populations of pelagic armorhead may not allow us to estimate the maximum sustainable yield. Recruitment rates and variability, the stockrecruitment relationships, and the basic ecological processes associated with seamount populations are unknown. Further, it is difficult to find other populations with which to make valid comparisons. Fish populations of seamounts are geographically isolated, but no evidence exists to suggest that stocks of dominant species are independent between seamounts. These issues will be important to address as we consider further research on seamount resources. It is the purpose of this paper to discuss hypotheses about the maintenance of seamount populations and to suggest future research.