Physiology and pathophysiology of trunk control

Abstract

IntroductionSince the first studies of population dynamics, the total mortality (Z) of exploited aquatic stocks hasnbeen presented as the sum of the fishing (F) and natural (N) mortalities. An implicit assumption ofnearly stock assessments was that the F component of this so-called Gompertz equation represented thenlanded catch. However, because few fishing gears are either completely selective for the targetednspecies and their sizes or entirely environmentally benign, in nearly all fisheries, such 'accounted' mortality is simply one component among a range of other, often indirect, unaccounted fishingnmortalities. In the mid 1990s, an international study group (under the auspices of the 'InternationalnCouncil for the Exploration of the Sea'), reduced F to qthe sum of all fishing-induced mortalities occurring directly as a result of catch or indirectly as a result of contact with or avoidance of thenfishing gearq, with at least 8 components, presented as:F = FC+ FB + FD + FE + FO + FG + FA + FHwhereFC Catch mortality: includes all landings from commercial, recreational and subsistence fishing;FB Misreported catch mortality: catches that are underestimated, misreported, or not reported;FD Discard mortality: organisms discarded (e.g. bycatch) after being landed by the fishing operation;FE Escape mortality: organisms that actively escape from a gear prior to the catch being landed by thenfishing operation;FO Drop-out mortality: captured organisms dying and dropping out of the gear prior to the catch beingnlanded by the fishing operation;FG Ghost fishing mortality: organisms caught in discarded or lost components of fishing gears;FA Avoidance mortality: directly or indirectly associated with organisms actively avoiding a fishingngear; andFH Habitat degradation mortality: associated with the degradation of an aquatic environment due to anfishing activity.In addition, other mortalities associated with predation (FP) and infection (F0 were identified as beingnsub-components of FD to FH above.There is overwhelming evidence of the potential for cumulative influences of the componentsnof unaccounted fishing mortality listed above on the total mortality of organisms encountering fishingngears, and especially FD (i.e. the mortality of discarded bycatch), that have contributed towards stockncollapses and the degradation of marine habitats around the world. In recent years, a paradigm shiftntowards the ecosystem-based management of fisheries has identified the need for a more holisticnapproach towards controlling the exploitation of marine resources; an integral component of which isnadequate information on the full range of impacts of fishing gears, and ways that negative aspects cannbe eliminated, or at least mitigated.All of my publications presented in this thesis support a broad strategy that encapsulates thenscience and technology required to work towards fulfilling the above objectives for various fisheries.nThe key stages of this protocol are (i) to identify the potential for problematic components ofnunaccounted fishing mortality, and then examine and validate appropriate technical-based mitigationnmeasures (ii) within and, if required, (iii) beyond existing fishing gear configurations, and then finallyn(iv) as part of changes to operational mechanisms. The extent to which I have applied the four stagesnof this generalized protocol to address unaccounted fishing mortality in different fisheries has variednaccording to many factors including, but not limited to, the temporal and spatial scale of the fishingnoperations, the level of perceived impacts, types of gears used, and the target and non-target speciesninvolved and their sizes. The logic underpinning this approach and my subsequent efforts within thenfour key stages are summarized below. n