Analysis of variance and standardization of longline hook rates of bigeye (Thunnus obesus) and yellowfin (Thunnus albacares) tunas in the Eastern Pacific Ocean during 1975-1987

Content Provider	Semantic Scholar
Author	Punsly, Richard G. Nakano, Hideki
Copyright Year	1992
Abstract	ENGLISH: Longline hook rates of bigeye and yellowfin tunas in the eastern Pacific Ocean were standardized by maximum depth of fishing, area, and season, using generalized linear models (GLM's). The annual trends of the standardized hook rates differ from the unstandardized, and are more likely to represent the changes in abundance of tunas in the age groups most vulnerable to longliners in the fishing grounds. For both species all of the interactions in the GLM's involving years, depths of fishing, areas, and seasons were significant. This means that the annual trends in hook rates depend on which depths, areas, and seasons are being considered. The overall average hook rates for each were estimated by weighting each 5-degree quadrangle equally and each season by the number of months in it. Since the annual trends in hook rates for each fishing depth category are roughly the same for bigeye, total average annual hook rate estimates are possible with the GLM. For yellowfin, the situation is less clear because of a preponderance of empty cells in the model. The full models explained 55% of the variation in bigeye hook rate and 33% of that of yellowfin. SPANISH: Se estandardizaron las tasas de captura con palangre de atunes patudo y aleta amarilla en el Oceano Pacifico oriental por la profunidad maxima de pesca, area, y temporada, usando modelos lineales generalizados (MLG). Las tendencias anuales de las tasas de captura estandardizadas son diferentes a las de las tasas no estandardizadas, y es mas que representen los cambios en la abundancia de los atunes en los grupos de edad mas vulnerables a los palangreros en las areas de pesca. Para ambas especies fueron significativas todas las interacciones en los MLG con ano, profundidad de pesca, area, y temporada. Esto significa que las tendencias anuales de las tasas de captura dependen de cual profundidad, area, y temporado se esta considerando. Para la estimacion de la tasa de captura general media para cada especie se pondero cada cuadrangulo de 5 grados igualmente y cada temporada por el numero de meses que contiene. Ya que las tendencias anuales en las tasas de captura para cada categoria de profundidad de pesca son aproximadamente iguales para el patudo, son posibles estimaciones de la tasa de captura anual media total con el MLG. En el caso del aleta amarilla, la situacion es mas confusa, debido a una preponderancia de celdas vacias en el modelo. Los modelos completos explican el 55% de la variacion de la tasa de captura de patudo y 33% de la del aleta amarilla. (PDF contains 19 pages.)
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Alternate Webpage(s)	https://www.iattc.org/PDFFiles/Bulletins/_English/Vol-20-No-4-1992-PUNSLY,%20RICHARD,%20and%20HIDEKI%20NAKANO_Analysis%20of%20variance%20and%20standardization%20of%20longline%20hook%20rates%20of%20BET%20and%20YFT%20in%20the%20EPO%20during%201975-1987.pdf
Language	English
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Resource Type	Article