Organization, functions, and achievements of the Inter-American Tropical Tuna Commission

ENGLISH: The Inter-American Tropical Tuna Commission (IATTC) operates under the authority and direction of a Convention originally entered into by the governments of Costa Rica and the United states. The Convention, which came into force in 1950, is open to the adherence by other governments whose nationals participate in the fisheries for tropical tunas in the eastern Pacific Ocean. The member nations of the Commission now are France. Japan, Nicaragua. Panama, and the United States. This report is a description of the organization, functions. and achievements of the Commission. It has been prepared to provide in a convenient format answers to requests for information concerning the Commission. It replaces similar, earlier reports (Carroz, 1965; Spec. Rep., 1), which are now largely outdated. SPANISH: La Comisión Interamericana del Atún Tropical (CIAT) funciona bajo la autoridad y dirección de un Convenio firmado originalmente por los gobiernos de Costa Rica y los Estados Unidos de America. El Convenio, Que entre en vigencia en 1950, se encuentra libre para Que otros gobiernos cuyos ciudadanos participan en la pesca de los atunes tropicales en el Océano Pacifico oriental se afilien a 61. Las naciones actuales que son miembros de la Comisión son: Francia, Japón, Nicaragua, Panamá y los Estados Unidos. Este informe es una descripci6n de la organización, funciones y resultados de la Comisión. Se ha preparado para suministrar en forma conveniente, informaci6n sobre la Comisión. Este informe renueva otros anteriores similares (Carroz, 1965; CIAT, Inf. Esp., 1) que en su mayor parte determinados.

Organization, functions, and achievements of the Inter-American Tropical Tuna Commission

This report is a description of the organization, functions, and achievements of the IATTC. It has been prepared to provide, in a convenient format, answers to requests for information concerning the IATTC. It replaces similar, earlier reports (Carroz, 1965; IATTC Spec. Rep., 1 and 5), which are now largely outdated. In order to make each section of the report independent of the others, some aspects of the IATTC are described in more than one section. For example, work on the early life history of tunas financed by the Overseas Fishery Cooperation Foundation of Japan is mentioned in the subsection entitled Finance, the subsection entitled Biology of tunas and billfishes, and the section entitled RELATIONS WITH OTHER ORGANIZATIONS. Due to space constraints, however, it is not possible to describe the IATTC's activities in detail in this report. Additional information is available in publications of the IATTC, listed in Appendix 6, and in its web site, www.iattc.org. Many abbreviations are used in this report. The names of the organizations or the terms are written out the first time they are used, and, for convenience, they are also listed in the Glossary.

Interactions of age-dependent mortality and selectivity functions in age-based stock assessment models

The natural mortality rate (M) of fish varies with size and age, although it is often assumed to be constant in stock assessments. Misspecification of M may bias important assessment quantities. We simulated fishery data, using an age-based population model, and then conducted stock assessments on the simulated data. Results were compared to known values. Misspecification of M had a negligible effect on the estimation of relative stock depletion; however, misspecification of M had a large effect on the estimation of parameters describing the stock recruitment relationship, age-specific selectivity, and catchability. If high M occurs in juvenile and old fish, but is misspecified in the assessment model, virgin biomass and catchability are often poorly estimated. In addition, stock recruitment relationships are often very difficult to estimate, and steepness values are commonly estimated at the upper bound (1.0) and overfishing limits tend to be biased low. Natural mortality can be estimated in assessment models if M is constant across ages or if selectivity is asymptotic. However if M is higher in old fish and selectivity is dome-shaped, M and the selectivity cannot both be adequately estimated because of strong interactions between M and selectivity.

Bessel functions and equations of mathematical physics

The aim of this dissertation is to introduce Bessel functions to the reader, as well as studying some of their properties. Moreover, the final goal of this document is to present the most well- known applications of Bessel functions in physics.

Beverton and Holt equations: spreadsheet functions and uncertainty

This contribution illustrates how modern spreadsheets aid the calculation and visualization of yield models and how the effects of uncertainties may be incorporated using Monte Carlo simulation. It is argued that analogous approaches can be implemented for other assessment models of simple to medium complexity justifying wider use of spreadsheets in fisheries analysis and training.