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EMA Ecosystem & Multispecies Modelling
Tuna Model
Wednesday, 26 August 2009 15:00

Tuna are highly specialized migrating species. They swim continuously to counterbalance their negative buoyancy, travelling hundreds of miles. This strategy has a high energy cost, forcing them to move in search of food and has resulted in morphological and physiological adaptations for thermoregulation and high oxygen extraction efficiency. Therefore, temperature and dissolved oxygen concentration affect tuna behavior significantly (Brill, 1994). Sea surface temperature and oxygen concentration have been used to define large-scale limits for potential tuna habitat (Barkley, Neill, & Gooding, 1978).  The tuna forage distribution might have also a major influence on tuna distribution. Surface tuna like skipjack and yellowfin tuna feed during daylight hours. Thus, water clarity is also likely to influence their distribution.

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Tuna Forage Model
Wednesday, 26 August 2009 14:59

An important component of SEAPODYM is the tuna forage sub-model that explores the dynamics of tuna prey organisms, consisting of macrozooplankton and micronekton, mainly crustaceans, fish and cephalopods from 2cm to 20 cm in size. The SEAPODYM team did not try to develop a detailed explicit food web model for the whole pelagic ecosystem in the Pacific Ocean, instead the tuna forage was considered as a single population.

icon Tuna Forage Model (225.92 kB)

 
Spatial Ecosystem and Population Dynamics Model (Seapodym)
Wednesday, 26 August 2009 14:56

Assessment of the historical, present and future states of marine ecosystem and the effects of human exploitation and climate variation have on the state of ecosystems are necessary to implement an ecosystem-based fishery management system. In particular, understanding how tuna, tuna-like populations and by-catch species respond to environment variation and anthropogenic changes (fishing pressure) is a major challenge for developing this approach. Modeling should be focused on comprehending the mechanisms linking the biological and physical components of marine ecosystems and exploring the responses of populations at higher trophic levels to different types of physical forcing, biological interactions, exploitation and they potential synergies.

Link to the Web SEAPODYM Access

icon SEAPODYM user manual (1.07 MB)

icon Tuna - SPC factsheet (3.8 MB)

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Ecopath
Tuesday, 14 April 2009 11:39

Fisheries model is a tool commonly used to understand and inform decision-makers of the consequences of possible fishing activities but also of environmental variation. Ecosystem effects of fishing are i) direct mortality on target species and incidental mortality on other biota and ii) indirect effects related to changes in the flow of energy through the ecosystem. Mutispecies models such as Ecopath are required to address the second effect.

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