Crecimiento del barrilete

INTER-AMERICAN TROPICAL TUNA COMMISSION COMISION INTERAMERICANA DEL ATUN TROPICAL
Bulle+in - Bole+:n

Vol. 11, No. 3

SCHOOLING HABITS OF YELLOWFIN TUNA I NEOTHUNNUS MACROPTERUSJ AND SKIPJACK IKATSUWONUS PELAMISJ IN THE EASTERN PACIFIC OCEAN AS INDICATED BY PURSE SEINE CATCH RECORDS. 1946..1955

HABITOS GREGARIOS DEL ATUN ALETA AMARILLA INEOTHUNNUS MACROPTERUSJ Y DEL BARRILETE IKATSUWONUSPELAMISJ EN EL OCEANO PACIFICO ORIENTAL. SEGUN LOS REGISTROS DE PESCA CON REDES DE ENCIERRE. 1946·1955

by - por
CRAIG J. ORANGE, MILNER B. SCHAEFER, and-yFRED M. LARMIE

La Jolla, California 1957

CONTENTS -

INDICE
Page

ENGLISH VERSION-VERSION EN INGLES INTRODUCTION SOURCES OF DATA AND THEIR COMPILATION Logbook records Statistical area system SPECIES COMPOSITION OF SCHOOLS Annualaverages for aH areas Annual and geographical variations Sorne general properties of species composition AMOUNT OF CATCH FROM SINGLE SCHOOLS Average catch-per-set Frequency distribution of catch.per.set. FIGURES-ILUSTRACIONES TABLES-TABLAS SPANISH VERSION-VERSION EN ESPAÑOL INTRODUCCION FUENTE DE LOS DATOS Y SU COMPILACION Registros en los cuadernos de bitácora Sistema estadístico de las áreas depesca COMPOSICION DE LOS CARDUMENES POR ESPECIES Promedios anuales para todas las áreas Variaciones anuales y geográficas..................... . Algunas propiedades generales de la composición por especies MONTO DE LAS PESCAS EFECTUADAS EN CARDUMENES INDEPENDIENTES Pesca promedio por calada Distríbución de las frecuencias de los montos de pesca por calada LITERATURE CITED-BIBLIOGRAFIA CITADA 114115 115 117 118 118 119 122 124 124 125 126 _ . 83 84 84 86 86 86 87 90 91 92 93 94 100

SCHOOLING HABITS OF YELLOWFIN TUNA (NEOTHUNNUS
MACROPTERUS) AND SKIPJACK (KATSUWONUS PELAMIS) IN THE

EASTERN PACIFIC OCEAN, AS INDICATED BY PURSE SEINE CATCH RECORDS, 1946-1955

by

Craig J. Orange, Milner B. Schaefer, and Fred M. Larmie

INTRODUCTION
The fishery in the Eastern Pacific Ocean forthe tropical tuna is supported by two species, the yellowfin tuna (Neotbunnus macropterus) and the skipjack (Katsuwonus pelamis) which occur in commercially important quantities from Baja California to Peru. Although there are some differences in the seasonal and geographical distributions of commercial concentrations of the two species, both are generally to be found in the same areas at the sameseasons. The catches landed by a commercial fishing vessel from a single trip normally consist of a mixture of the two species, and often the catch made in a single day ineludes substantial numbers of each of them. From reports of fishermen and from observations of scientists aboard commercial vesseIs, it appears that not infrequently schools are encountered consisting of a mixture of the twospecies. The degree of association of these tropical tuna species, that is the extent to which individual schools tend to be composed of only a single species, is of considerable interest, with regard not only to understanding the behavior patterns of these pelagic fishes, but also to devising practical fishing regulations at such time as they become necessary. It appears (Shimada and Schaefer 1956)that the yellowfin tuna are being fished at an intensity much nearer that corresponding to the maximum sustainable catch than are the skipjack. It may, therefore, become necessary to recommend regulations which will limit the catching of yellowfin without limiting the catching of skipjack. A second matter of interest is the sizes of schools into which the tropical tunas tend to aggregate. Theseaspects of the schooling habits of the yellowfin and skipjack tuna may be investigated by means of the logbook records of the catehes of individual sets of the nets of purse-seine vessels. For both purposes it must be assumed that a set is made, in each case, on a single school of fish. The study of sehool sizes based on these data requires the additional assumption either that the entire school is...