Eutrophication also enhances the proliferation of faster growing phytoplankton, epiphytic algae, and macroalgae that compete with seagrass for light and space (Kemp et al., 1983; Phillips et al., 1978; Short et al., 1995; Twilley et al., 1985). Species that can be extinct include, eel, Atlantic code, sea bass, sturgeon, etc. Each trawl track is a small disturbance, but over a long enough period and with widespread coverage, the small changes can result in a large effect. This design often involves direct sampling of fauna, video observations, and sonar scans of the control and disturbed sites. Otter trawls have been evaluated more often than have other types of gear, because of their widespread use (Barnette, 2001; Collie et al., 2000a). There has been an increase in the understanding of fishing gear and habitat interactions that can be used for making decisions about habitat management.Any fishing gear will affect the flora and fauna of a given location to some degree, but the magnitude and duration of the effect depends on several factors, including gear configuration, towing speed, water depth, and the substrate over which the tow occurs. Ecological disturbance theory also suggests that, even if each individual pulse disturbance does not have a large acute effect, there could be a threshold of intensity or a cumulative level beyond which persistent changes in the ecosystem occur.
Its duration may vary. The return time to the initial stage has been predictable in some cases. Mobile gear reduces benthic habitat complexity by removing or damaging the actual physical structure of the seafloor, and it causes changes in species composition. Resilience is the degree to which an ecosystem’s long-standing composition, structure, and function can recover from disturbance (Holling, 1973). Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.Do you want to take a quick tour of the OpenBook's features?Do you enjoy reading reports from the Academies online Because water content and pore water turnover are important determinants of nutrient regeneration in marine sediments (Hopkinson et al., 1999), hydraulic dredging could alter the nutrient flux.Bottom trawling and dredging can both resuspend and bury biologically recyclable organic material, changing the flow of nutrients through the food web (Mayer et al., 1991). Trawling is an approach in fishing that involves pulling fishing nets through nets behind at least one boat. Seagrass ecosystems are important habitats and locations of fisheries for numerous fish and invertebrate species. Mortality rates for species that migrate become uncoupled from the physical attributes of habitat because their growth occurs at stages that are earlier than found in species that move less often and have greater affinities for habitat.
In other cases, with nonlinear interactions and multiple-equilibrium states, the time the ecosystem will remain in a new state is not predictable.
This research should include quantitative studies undertaken in deeper water (>100 m) and studies in stable and structurally complex habitats, for which the recovery trajectory will be measured in years to decades. Despite that, we can make some observations about the amount of physical disturbance that is sustainable in some types of habitat. An alternative approach recognizes multiple-equilibria, non-linearity, and threshold effects (Holling, 1973; Holling et al., 1995; Patten and Constanza, 1997). What are the short- and long-term effects on populations, community structure, and interspecific dynamics? Mortality of adults can be attributed to disease, senescence, predation from sharks and other large piscivores, and fishing.The relatively few studies of the indirect effects of trawling and dredging on marine ecosystems show results that are consistent with the basic principles of marine ecosystem dynamics and predator–prey interactions. Clearly, habitats with extended recovery periods are strong candidates for protection from disturbance caused by fishing. It causes the collapse of benthic biodiversity and ecosystem functions.
Flora and megafauna to a depth of 10 cm are damaged.• Dredge tracks remain visible for 2.5 years in maerl habitats.• Maerl is a “living sediment” that is slow to recover from disturbance due to extremely low growth rates (5)A gradient of increasing large epifaunal cover correlated with decreasing fishing effort (4)• Undredged sites had higher numbers of organisms, biomass, species richness, and species diversity than dredged sites.