The targets are based on models of the expected yield for every crab entering the population, but researchers acknowledge that there is an apparent uncoupling of spawning stock size and subsequent recruitment in this blue crab stock. He noted that crabs are able to exploit a variety of habitats over the course of their life history, an observation supported by T. Hines who noted that crabs require an array or mosaic of habitat types to thrive. The actual make-up of these mosaics may vary and crabs appear to be adaptable to change. Stevenson suggested that research is needed to assess what types of alternate substrates can fill the role once provided by SAV and to what extent the decline of grasses impacts population levels. Marshes and small creek systems may play an important role for large adult crabs, while woody debris may be essential for juveniles.
Anthropogenic influences have the potential to impact populations as well.
New shoreline structures such as rip rap, jetties and piers may provide suitable physical substrate and cover while removal of woody debris for esthetic or navigational purposes has the potential to have a negative impact. Another important habitat issue is that of contaminants. Little is known regarding the impact that a variety of chemical contaminants present in the ecosystem have on the health of the blue crab population. Hence, anthropogenic alterations result in complex impacts that need to be assessed carefully within the context of crab biology and population dynamics. Stevenson's presentation emphasized that habitat issues and responses in this area must consider multiple factors.