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Sustainability in fisheries is a complex concept and one that has attracted a rich history of research over time. The basic concerns of sustainability are how to reconcile ecological, economic and social requirements within the perspectives of intra- and inter-generational equity. Therefore, maintaining these requirements simultaneously is critical to achieving a perennial system and avoiding so-called “crisis” situations. It is contended that viability theory, which is a relatively new area of mathematics, rigorously captures the essence of sustainability. Using viability theory, this thesis develops two viability models based on different direct conservation measures (i.e. input and output controls) to examine the feasibility conditions under which a regulator can achieve sustainability in a fishery characterised by a “by-catch process”, whereby one species is targeted and another species is incidentally caught as by-catch. The first model considers a by-catch fishery where fishing input is controlled by a regulator. The second model considers two interrelated fisheries managed using a dual quantity-price system, which is based on New Zealand’s Quota Management System (QMS). For each model, the set of constraints representing the “good health” of the system are characterised using managerial priorities identified in the literature. Then, the viability kernel, which is the largest set of initial states for which there are controls that result in inter-temporal trajectories satisfying all the constraints, is approximated numerically. This is achieved by employing VIKAASA, which is a computer application capable of generating kernel approximations. The viability kernel provides the regulator with meaningful reference values and indicators for desirable or undesirable states of the fishery, which serve as important inputs into policy decisions. This study also shows the potential for viability theory to provide policy makers with a better insight of how to integrate e

This review aims at comparing the fisheries management systems existing in New Zealand and in the European Union. The involvement of stakeholders at all stages of the management process is generally more transparent and better established in New Zealand than in the EU. Both systems aim at achieving an adequate balance between sustainability and utilisation and consider the precautionary approach as a founding principle. The social objectives are probably more explicit in the EU management system. In New Zealand, B-MSY is a legal management target for all stocks in the quota management system (QMS), but management strategies were poorly explicit until most recently. In the EU, there have not been any legal management targets or strategies until 1999. Since 1999, a number of multi-annual recovery and management plans have been established, including both management targets and strategies. Both management systems include conservation and access regulation measures. The EU management measures aim at regulating fisheries outputs and inputs, and discarding is tolerated. New Zealand management is almost exclusively output-based, and discarding practices are banned. In the EU, while individual quotas (IQs) are implicit in several countries, there is no consistent pattern across Member States for allocating TACs. In New Zealand, individual transferable quotas (ITQs) are implemented, and some flexibility in catch-quota balancing is provided by a carry-over allowance and the payment of a landing tax, the deemed value, for every fish landed above quota. If rights-based management were introduced in the EU based on, e. g., the New Zealand model, we suggest that concentration rules be set in accordance with the social objectives of the Common Fisheries Policy, and also that the deemed value should be set based on science and economics.

Managing adequately the exploitation of commercial species subject to technical interactions is a key step towards the ecosystem approach to fisheries. We evaluate here, using a bio-economic modelling approach building on the ISIS-Fish simulation platform, the relative impact of total allowable commercial catches (TACC) and of taxes applicable to over-quota landings (deemed value) on the sustainability of a selection of species exploited by the New Zealand hoki (Macruronus novaezelandiae) fishery. We investigate some aspects of the hoki mixed fisheries, consisting of four fleets and nineteen metiers, by considering the technical interactions between hoki and Southern hake (Merluccius australis). The dynamics of effort allocation were modelled using gravity model, using value per unit of effort (VPUE) as attractivity coefficient. Several management scenarios, based on different levels of TACC, effort limits and deemed value have been defined. The impact of these strategies on spawning biomass and catches has been investigated. The results confirm that the deemed value may, in combination with TACC, be an efficient management tool. By increasing the hoki deemed value, we could somehow limit the decrease in the hoki TACC needed to harvest Western hoki sustainably. Constraining hoki fishing also restricts Southern hake fishing in the Chatham Rise and in the West Coast South Island, but leads to increased targeting of this species in the Sub-Antarctic area. The relative costs of renting/buying quota or paying the deemed value are most constraining when the hoki TACC is at relatively low level and when the hoki deemed value is more than 1.5 times the current value.

This study describes the New England Otter Trawl Fishery between 1982 and 1998 and the potential economic impacts of regulations on the Northeastern Multispecies Groundfish Fishery (MGF). The study uses primary data collected by the author and secondary data obtained from the National Marine Fisheries Service (NMFS). This research required extensive econometric analysis of both value landed and cost data. The landed value is influenced by the vessel's physical characteristics, port of landing, seasonal choices of fishing gear-species combinations, days at sea and distance from shore, and the captain's skill (also referred to as the “skipper effect”). The vessel-cost model is composed of several equations, each corresponding to one of the following annual cost items: Trip Expenses - Other Variable Costs - Indivisible Operating Costs - 5 year Overhaul - Depreciation and Interests - Crew Benefits and Crew Bonuses. The estimated equations are used to synthesize an economic model of vessel behavior, which can be used to examine the economic consequences of alternative scenarios. This model was used to examine the impacts of selected regulations on the fishing industry. The results indicate differential impacts, which affect larger vessels (especially above 90 feet). The statistics show that some vessels modify their fishing habits by re-targeting their catch to different species and/or by changing how far they are willing to go fishing. These changes affected essentially geographic and seasonal effort distribution for both large and small trawlers. Larger vessels are fishing more inshore than before and for less valuable species thus bringing more pressure on inshore fish stocks. The results also shed light on the relative efficiency of large and small vessels, although they suggest that the issue is ill phrased!—small (50 to 60 ft) vessels appear more efficient than larger vessels when both are operating near shore. However, smaller vessels are not sufficiently seaworth