Measures of population density and concentration of fishing effort for yellowfin and skipjack tuna in the eastern Tropical Pacific Ocean 1951-1959

ENGLISH: In a previous Bulletin of this Commission, Griffiths (1960) discussed two indices of population density and an index of concentration of fishing effort of bait boats for yellowfin tuna in the Eastern Tropical Pacific for the 1951-1956 period. Yellowfin and skipjack tuna occur in the same general fishing areas and many of the commercial catches are composed of a mixture of the two species. It is desirable, therefore, to extend the investigation to skipjack and to the two species combined. SPANISH:En un Boletín anterior de esta Comisión, Griffiths (1960) se refiere a dos índices de la densidad de la población y a un índice de la concentración del esfuerzo de pesca de los barcos de carnada sobre el atún aleta amarilla en el Pacífico Oriental Tropical, correspondientes al período 1951-1956. Los atunes aleta amarilla y barrilete se encuentran en las mismas áreas generales de pesca y muchas de las pescas comerciales están compuestas de una mezcla de las dos especies. Es deseable, por lo tanto, ampliar la investigación en lo que se refiere al barrilete y a las dos especies combinadas.

Fishing Long-Fingered Bats (Myotis capaccinii) Prey Regularly upon Exotic Fish

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Exploratory fishing for tunas and tuna tagging in the Marquesas, Tuamotu, Society, Pitcairn, and Gambier Islands

The Marquesas Islands are located in the Pacific Ocean at about 9 degrees south latitude and 140 degrees west longitude (Figure 1). It has been demonstrated by tagging (Anonymous, 1980b) that skipjack tuna, Katsuwonus pelamis, which occur in the northeastern Pacific Ocean have migrated to the Hawaiian Islands and Christmas Island in the central Pacific and also to the area between the Marshall and Mariana islands in the western Pacific. The Tuamotu, Society, Pitcairn, and Gambier islands, though the first two are not as close to the principal fishing areas of the eastern Pacific Ocean as are the Marquesas Islands, and the last two are small and isolated, are of interest for the same reasons that the Marquesas Islands are of interest, and thus skipjack should be tagged in those islands for the same reason that they should be tagged in the Marquesas Islands. The organizations which participated in the Marquesas Islands tagging and other scientific activities were the Inter-American Tropical Tuna Commission (IATTC), the South Pacific Commission (SPC), the Centre National pour l'Exploitation des Oceans (CNEXO), the Office de la Recherche Scientifique et Technique Outre-Mer (ORSTOM), the Service de la Peche de la Polynesie Francaise (SPPF), and the Service de l'Economie Rural (SER).

A modeling approach to identify optimal habitat and suitable fishing grounds for neon flying squid (Ommastrephes bartramii) in the Northwest Pacific Ocean

We developed a habitat suitability index (HSI) model to understand and identify the optimal habitat and potential fishing grounds for neon f lying squid (Ommastrephes bartramii) in the Northwest Pacific Ocean. Remote sensing data, including sea surface temperature, sea surface salinity, sea surface height, and chlorophyll-a concentrations, as well as fishery data from Chinese mainland squid f leets in the main fishing ground (150–165°E longitude) from August to October, from 1999 to 2004, were used. The HSI model was validated by using fishery data from 2005. The arithmetic mean modeling with three of the environmental variables—sea surface temperature, sea surface height anomaly, and chlorophyll- a concentrations—was defined as the most parsimonious HSI model. In 2005, monthly HSI values >0.6 coincided with productive fishing grounds and high fishing effort from August to October. This result implies that the model can reliably predict potential f ishing grounds for O. bartramii. Because spatially explicit fisheries and environmental data are becoming readily available, it is feasible to develop a dynamic, near real-time habitat model for improving the process of identifying potential fishing areas for and optimal habitats of neon flying squid.

Recreational anglers and fishing guides from an estuarine protected area in southeastern Brazil: Socioeconomic characteristics and views on fisheries management

The Iguape and Cananéia Lagoon-Estuarine Complex is a biodiversity hotspot in southeastern Brazil. In recent decades, the region has become an important destination for recreational fishing. The objective of this study was to analyze the socioeconomic characteristics of visiting anglers and fishing guides working in the Cananéia-Iguape-Peruíbe Environmental Protected Area and their views on fisheries management. Data were collected through semi-structured interviews conducted between January 2009 and January 2010. We interviewed 278 anglers, who were predominantly male (93%) with a mean age of 47 years and from the state of São Paulo. The targeted species were snooks (Centropomus undecimales and Centropomus parallelus) and weakfishes (Cynoscion leiarchus and Cynoscion acoupa). Only half the anglers had the mandatory fishing license, and many of them lacked knowledge about catch quotas and minimum size requirements for specific species. The fishing guides (n = 80) were all male, with a mean age of 39 years and extensive experience. Most of the guides believe that the study area is somewhat degraded due to the removal of riparian vegetation, siltation, pollution, and especially the depletion of fish stocks. The opinions of the stakeholders (anglers and guides) converge on the high priority needs of the fishery and possible management actions regarding recreational fishing, such as improved fisheries enforcement (first in order of importance), proper training of fishing guides, zoning of fishing areas, and the definition of a maximum size limit. © 2013 Elsevier Ltd.

Application of stable isotope analysis to differentiate shrimp extracted by industrial fishing or produced through aquaculture practices.

Carbon and nitrogen stable isotope values were determined in Pacific white shrimp (Litopenaeus vannamei) with the objective of discriminating animals produced through aquaculture practices from those extracted from the wild. Farmed animals were collected at semi-intensive shrimp farms in Mexico and Ecuador. Fisheries-derived shrimps were caught in different fishing areas representing two estuarine systems and four open sea locations in Mexico and Ecuador. Carbon and nitrogen stable isotope values (13CVPDB and 15NAIR) allowed clear differentiation of wild from farmed animals. 13CVPDB and 15NAIR values in shrimps collected in the open sea were isotopically enriched (−16.99‰ and 11.57‰), indicating that these organisms belong to higher trophic levels than farmed animals. 13CVPDB and 15NAIR values of farmed animals (−19.72‰ and 7.85‰, respectively) partially overlapped with values measured in animals collected in estuaries (−18.46‰ and 5.38‰, respectively). Canonical discriminant analysis showed that when used separately and in conjunction, 13CVPDB and I5NAIR values were powerful discriminatory variables and demonstrate the viability of isotopic evaluations to distinguish wild-caught shrimps from aquaculture shrimps. Methodological improvements will define a verification tool to support shrimp traceability protocols.

Additional information on the length-weight relationship of skipjack tuna from the Eastern Tropical Pacific Ocean

ENGLISH: Results of a study of the length-weight relationships of yellowfin (Neothunnus macropterus) and skipjack (Katsuwonus pelamis) tuna from several fishing areas of the Eastern Tropical Pacific Ocean have been published by Chatwin (1959). In that report, a very low exponential value of 2.6261 was obtained for skipjack from Area 14 (off northern Chile, see Chatwin, Figure 1). It was pointed out, however, that this estimate was based on two samples of fish with a very narrow range of total lengths, not representative of the range in the catch, and that it would be desirable to obtain a further estimate based on a larger range of total lengths. In addition, there proved to be significantly large differences among exponents for the areas sampled, precluding use of a single regression equation for all areas. Two important fishing areas remained unsampled (Areas 10 and 13, see Chatwin, Figure 1), and it appeared desirable to collect length-weight measurement data from them, so that estimating equations would be available for all areas. Subsequent to publication of Chatwin's study, samples of skipjack length-weight measurements were obtained from the desired areas. Estimates derived from these data, and their effects on the previous analysis are presented herein. SPANISH:Los resultados de un estudio sobre las relaciones entre la longitud y el peso del atún aleta amarilla (Neothunnus macropterus) y del barrilete (Katsuwonus pelamis) de las diferentes áreas de pesca en el Pacífico Oriental Tropical ya han sido publicados por Chatwin (1959). En ese informe se obtuvo un valor exponencial muy bajo de 2.626 para el barrilete del Area 14 (frente a la costa norte de Chile, ver Chatwin, Figura 1). Se hizo hincapié, sin embargo, en que esta estimación se basaba en dos muestras de peces con una amplitud muy estrecha de longitudes totales, no representativa de la amplitud en la pesca, y que sería deseable obtener una estimación adicional basada en una amplitud mayor de longitudes totales. Además, se comprobó que habian diferencias significativamente grandes entre los exponentes de las áreas muestreadas lo que impedía el usa de una sola ecuación de regresión para todas las áreas. Se quedaron sin muestrear dos importantes áreas de pesca (Areas 10 y 13, ver Chatwin, Figura 1) y pareció deseable recolectar datos de medidas de longitud y peso de estas áreas, de tal manera que hubiesen disponibles ecuaciones estimadoras para todas las áreas. Después de la publicación del estudio de Chatwin, so obtuvieron muestras de medidas de longitud y peso de barriletes de las áreas deseadas. Las estimaciones derivadas de estos datos y sus efectos sabre el análisis previo se dan en el presente informe.

Distribution of Atlantic menhaden, Brevoortia tyrannus, purse-seine sets and catches from southern New England to North Carolina, 1985-96

Sets and catches of Atlantic menhaden, Brevoortia tyrannus, made in 1985-96 by purse-seine vessels from Virginia and North Carolina were studied by digitizing and analyzing Captain's Daily Fishing Reports (CDFR's), daily logs of fishing activities completed by captains of menhaden vessels. 33,674 CDFR's were processed, representing 125,858 purse-seine sets. On average, the fleet made 10,488 sets annually. Virginia vessels made at least one purse-seine set on 67%-83% of available fishing days between May and December. In most years, five was the median number of sets attempted each fishing day. Mean set duration ranged from 34 to 43 minutes, and median catch per set ranged from 15 to 30 metric tons (t). Spotter aircraft assisted in over 83% of sets overall. Average annual catch in Chesapeake Bay (149,500 t) surpassed all other fishing areas, and accounted for 52% of the fleet's catch. Annual catch from North Carolina waters (49,100 t) ranked a distant second. Fishing activity in ocean waters clustered off the Mid-Atlantic states in June-September, and off North Carolina in November-January. Delaware Bay and the New Jersey coast were important alternate fishing grounds during summer. Across all ocean fishing areas, most sets and catch occurred within 3 mi. of shore, but in Chesapeake Bay about half of all fishing activity occurred farther offshore. In Virginia, areas adjacent to fish factories tended to be heavily fished. Recent regulatory initiatives in various coastal states threaten the Atlantic menhaden fleet's access to traditional nearshore fishing grounds. (PDF file contains 26 pages.)

Estimation of year class abundance and mortality of yellowfin tuna in the Eastern Tropical Pacific

ENGLISH: Age composition of catch, and growth rate, of yellowfin tuna have been estimated by Hennemuth (1961a) and Davidoff (1963). The relative abundance and instantaneous total mortality rate of yellowfin tuna during 1954-1959 have been estimated by Hennenmuth (1961b). It is now possible to extend this work, because more data are available; these include data for 1951-1954, which were previously not available, and data for 1960-1962, which were collected subsequent to Hennemuth's (1961b) publication. In that publication, Hennemuth estimated the total instantaneous mortality rate (Z) during the entire time period a year class is present in the fishery following full recruitment. However, this method may lead to biased estimates of abundance, and hence mortality rates, because of both seasonal migrations into or out of specific fishing areas and possible seasonal differences in availability or vulnerability of the fish to the fishing gear. Schaefer, Chatwin and Broadhead (1961) and Joseph etl al. (1964) have indicated that seasonal migrations of yellowfin occur. A method of estimating mortality rates which is not biased by seasonal movements would be of value in computations of population dynamics. The method of analysis outlined and used in the present paper may obviate this bias by comparing the abundance of an individual yellowfin year class, following its period of maximum abundance, in an individual area during a specific quarter of the year with its abundance in the same area one year later. The method was suggested by Gulland (1955) and used by Chapman, Holt and Allen (1963) in assessing Antarctic whale stocks. This method, and the results of its use with data for yellowfin caught in the eastern tropical Pacific from 1951-1962 are described in this paper. SPANISH: La composición de edad de la captura, y la tasa de crecimiento del atún aleta amarilla, han sido estimadas por Hennemuth (1961a) y Davidoff (1963). Hennemuth (1961b), estimó la abundancia relativa y la tasa de mortalidad total instantánea del atún aleta amarilla durante 1954-1959. Se puede ampliar ahora, este trabajo, porque se dispone de más datos; éstos incluyen datos de 1951 1954, de los cuales no se disponía antes, y datos de 1960-1962 que fueron recolectados después de la publicación de Hennemuth (1961b). En esa obra, Hennemuth estimó la tasa de mortalidad total instantánea (Z) durante todo el período de tiempo en el cual una clase anual está presente en la pesquería, consecutiva al reclutamiento total. Sin embargo, este método puede conducir a estimaciones con bias (inclinación viciada) de abundancia, y de aquí las tasas de mortalidad, debidas tanto a migraciones estacionales dentro o fuera de las áreas determinadas de pesca, como a posibles diferencias estacionales en la disponibilidad y vulnerabilidad de los peces al equipo de pesca. Schaefer, Chatwin y Broadhead (1961) y Joseph et al. (1964) han indicado que ocurren migraciones estacionales de atún aleta amarilla. Un método para estimar las tasas de mortalidad el cual no tuviera bias debido a los movimientos estacionales, sería de valor en los cómputos de la dinámica de las poblaciones. El método de análisis delineado y usado en el presente estudio puede evitar este bias al comparar la abundancia de una clase anual individual de atún aleta amarilla, subsecuente a su período de abundancia máxima en un área individual, durante un trimestre específico del año, con su abundancia en la misma área un año más tarde. Este método fue sugerido por Gulland (1955) y empleado por Chapman, Holt y Allen (1963) en la declaración de los stocks de la ballena antártica. Este método y los resultados de su uso, en combinación con los datos del atún aleta amarilla capturado en el Pacífico oriental tropical desde 1951-1962, son descritos en este estudio.

Studies on the Japanese long-line fishery for tuna and marlin in the Eastern Tropical Pacific Ocean during 1963

ENGLISH: During 1963, the area of operation of the Japanese long-line fishery in the eastern Pacific further expanded, and total fishing effort increased. Charts are presented showing the distribution of effort and of catch-rates, by species, for major fishing areas; and showing catch-rates by species, by quarters of the year, by areas of one-degree of latitude and longitude. In the newly-exploited region north of 10°N, yellowfin and striped marlin are principal elements of the catch, while in the newly-fished region south of the former fishing areas, south of about 20°S, albacore dominate in the catch. Continued decline in catch rates of bigeye tuna, associated with increased fishing effort, indicates that there has been a real decrease in abundance of this species, and that it may have resulted from effects of the fishery on the stock. Changes in catch rates of yellowfin tuna seem to be associated with effects on the stock by both the long-line fishery and by the near-surface fishery by purse-seiners and bait-boats. Over the short series of years for which data are available, there are no discernible trends in apparent abundance of striped marlin or albacore. Information is presented concerning seasonal and geographical distributions of spawning yellowfin tuna, based on examination of gonads. Analysis of data on size composition of yellowfin tuna for 1958-1964 indicates that the long-line fishery is becoming increasingly dependent on the most recently recruited year class, further confirming the effect of the fishery on the stock. The long-line fishery now takes nearly all of its catch of yellowfin tuna from two year-classes each year, during their third and fourth years of life. SPANISH: Durante 1963 el área de operación de la pesca palangrera japonesa en el Pacífico oriental se extendió más y se incrementó el esfuerzo total de pesca. Se presentan cartas indicando la distribución del esfuerzo y las tasas de captura por especies, para las áreas principales de pesca; y se muestran las tasas de captura por especies y por trimestres del año en áreas de un grado de latitud y longitud. En la región recientemente explotada al norte de los 10°N, los principales elementos de la captura son el atún aleta amarilla y el marlín rayado, mientras aproximadamente al sur de los 20°S en la región recientemente pescada al sur de las primeras áreas de pesca la albacora predomina en la captura. La continua merma en las tasas de captura del patudo en asociación con el incremento en el esfuerzo de pesca, indica que ha habido una real reducción en la abundancia de esta especie y que puede ser el resultado de los efectos de la pesquería sobre el stock. Los cambios en las tasas de captura del atún aleta amarilla parecen estar asociados con los efectos sobre el stock tanto de la pesquería palangrera como de la pesca de superficie por barcos rederos y de carnada. No hay tendencias perceptibles en la abundancia aparente del marlín rayado o la albacora en el corto período de años de los que se disponen datos. Se presenta información referente a la distribución estacional y geográfica del desove del atún aleta amarilla basado en el examen de las gónadas. El análisis de los datos sobre la composición de tallas del atún aleta amarilla correspondiente a 1958-1964 indica que la pesca palangrera depende cada vez más de las clases anuales recientemente reclutadas, confirmando aún más el efecto que tiene la pesquería sobre el stock. La pesquería palangrera coge casi toda su pesca de atún aleta amarilla de dos clases anuales cada año, durante su tercer y cuarto año de vida. (PDF contains 70 pages.)

Spawning of yellowfin tuna and the discrimination of subpopulations

ENGLISH: The spawning of yellowfin tuna (Thunnus albacares) in the eastern Pacific Ocean was examined to ascertain the existence of separate subpopulations within this area. Investigations of biochemical genetics of yellowfin indicate that there are a number of genetically distinct groups in the eastern Pacific. In addition, yellowfin belong to two recruitment cohorts, X and Y, which are composed of a mixture of these genetically different groups. Spawning data were collected from 1956 through 1961 from the coastal fishing grounds, and from 1970 through 1973 from the offshore fishing areas. Temporal and spatial aspects of spawning of the fish of the two cohorts were analyzed to determine if yellowfin spawning behavior supports the existence of genetically separate subpopulations. Spawning condition was inferred from the maturity of the ovaries. It was found that the coastal fish of each cohort exhibit at least two spawning periods per year which vary in length and time of occurrence from year to year. Fish taken from the offshore fishing grounds did not exhibit this variable spawning pattern. Although samples were not available for all months, the data showed that each cohort has a spawning period of at least 7 months and may spawn year around. Samples from offshore areas also had much higher percentages of spawners than those from the coastal areas. Temporal differences in spawning are not maintaining the genetically separate groups found in the fishery, since fish of both recruitment cohorts spawn at the same time. Also, fish of both the X and Y cohorts spawned in all areas examined; however, these data are insufficient to determine whether spatial isolation of spawning groups is occurring within the areas. SPANISH: Se examinó el desove del atún aleta amarilla (Thunnus albacares) en el Océano Pacífico oriental para averiguar la existencia de subpoblaciones separadas en esta zona. La investigación genética bioquímica del aleta amarilla indica que existen varios grupos genéticamente distintos en el Pacífico oriental. Además, el aleta amarilla pertenece a dos cohortes de reclutamiento X e Y, formadas por una mezcla de estos grupos genéticamente diferentes. Los datos del desove fueron obtenidos de 1956 a 1961, en las regiones neríticas de pesca y desde 1970 a 1973, en las áreas oceánicas de pesca. Se analizaron los aspectos temporales y espaciales del desove de los peces de las dos cohortes, para determinar si el comportamiento reproductor del aleta amarilla, apoya la existencia de subpoblaciones genéticamente diferentes. Se derivó la condición del desove según la madurez de los ovarios. Se encontró que los peces costeros de cada cohorte exhibían por lo menos dos períodos anuales de desove que varían en duración y fecha de ocurrencia de un año a otro. Los peces capturados en las regiones oceánicas de pesca no exhibieron este patrón variable de desove. Aunque o se consiguieron muestras en todos los meses, los datos indican que cada cohorte tiene un período de desove por lo menos de 7 meses y puede que desoven durante todo el año. Las muestras de las regiones oceánicas tuvieron porcentajes mucho mayores de reproductores que los de las zonas neríticas. Las diferencias temporales en el desove no sirven para explicar la presencia de grupos genéticamente separados que se encuentran en la pesca, ya que los peces de ambas cohortes de reclutamiento desovan al mismo tiempo. Además, los peces de ambas cohortes (X e Y) desovan en todas las zonas examinadas; sin embargo, estos datos no son suficientes para determinar si el aislamiento de los grupos de desove ocurre en las zonas. (PDF contains 53 pages.)

Die europäischen Krabbenanlandungen der letzten Jahre: Deutschland Nr. 1

Fishery on brown shrimp has developed towards one of the most important fisheries in the North Sea area in economic terms. Statistical data on European wide landings have been gathered by a working group of the International Council for the Exploration of the Sea. They show relatively stable shares of approximately 50% for Germany, 38% for the Netherlands and 8% for Denmark. Further production originates from Great Britain, France and Belgium. The new log-book regulation of the EU will give similar data improved by better information on fishing areas and fishing effort.

The influence of some environmental variables on the apparent abundance of skipjack tuna, Katsuwonus pelamis, in the Eastern Pacific Ocean

ENGLISH: The abundance of skipjack larvae in the central and western Pacific approximately doubled for every 1°C increase in sea-surface temperature (SST) from 23°C to a maximum of about 29°C, and then usually decreased with further increases in SST. Skipjack larvae are scarce in the eastern Pacific Ocean (EPO), so most skipjack recruits and adults in this area are believed to have originated in the central and, possibly, the western Pacific. The catch per unit of effort (CPUE), in short tons per day's fishing, and the catch rate, in number of fish per day's fishing, are estimates of apparent abundance in a fishery. The logarithm of the annual CPUE for skipjack for international baitboats in the EPO for the 1934-1960 period was positively correlated with SST in the spawning area in the central Pacific 18 months earlier (r2 0.31), during the July-June period when most of the recruits in each cohort were presumed to have been spawned. Adequate data for other environmental variables were not available for testing with the baitboat data. The other environmental variables available and selected for testing for correlation with estimates of skipjack abundance for purse seiners for the 1961-1984 period and the reasons for their selection are as follows. 1)Wind-mixing index (WMI). The degree of mixing in the upper layers of the ocean is proportional to the cube of the wind speed, called WMI. The degree of mixing in the spawning areas of the central and the western Pacific may affect the concentration of organisms that skipjack larvae feed upon, thereby influencing their survival, and ultimately determining cohort strength and the number of recruits to the eastern Pacific fishery. 2) SST in the fishing areas at the time of fishing (SST). The CPUE for yellowfin tuna has been shown to be inversely related to SST in the fishing areas, and there are indications that skipjack CPUE is lower during EI Nino events when SST is higher than normal. 3) North-south SST gradient across the thermal front off the Gulf of Guayaquil. This is a measure of the degree of upwelling and nutrient enrichment of the upper waters south of the front and ultimately of the production of food for tunas. 4) Speed of the North Equatorial Countercurrent (NECC). Young skipjack may migrate from the central Pacific to the EPO in the eastward flowing NECC; if so, the number of recruits might be affected by variations in the speed of the current. The logarithm of the annual catch rate of skipjack recruits by international purse seiners in the EPO for the 1961-1984 period was positively correlated with SST in the spawning area of the central Pacific 18 months earlier (r2 = 0.21),and inversely correlated with WMI in the spawning area 18 months earlier (r2 0.46). The logarithm of CPUE for purse seiners in the area off the Gulf of Guayaquil was not correlated with SST in the spawning area 18 months earlier, but was inversely correlated with WMI in the spawning area 18 months earlier (r2 = 0.19), and inversely correlated with the north-south SST gradient in the fishing area at the time of fishing (r2 0.32). Neither of these estimates of apparent abundance from purse seiners were correlated with SST in the fishing areas, or with the speed of the NECC at earlier times. SPANISH: La abundancia de larvas de barrilete en el Pacífico central y occidental se multiplicó por dos, aproximadamente, por cada aumento de 1°Cen la temperatura de la superficie del mar (TSM) entre 23°C y un máximo de unos 29°C, y luego generalmente disminuyó con más aumentos en la TSM. Las larvas de barrilete son escasas en el Océano Pacífico oriental (OPO), y por lo tanto se cree que la mayoría de los reclutas y adultos en esta zona surgieron del Pacífico central, y posiblemente también del Pacífico occidental. La captura por unidad de esfuerzo (CPUE), en toneladas cortas por día de pesca, y la tasa de captura, en número de peces por día de pesca, son estimaciones de la abundancia aparente en una pesquería. El logaritmo de la CPUE anual de barrilete lograda por barcos de carnada en el OPO en el período 1934-1960 se correlacionó positivamente con la TSM en la zona de desove en el Pacífico central de 18 meses antes (r2 = 0.31), durante el período de junio-julio en el cual se cree que nació la mayoría de los reclutas en cada cohorte. No se dispuso de datos suficientes sobre otras variables ambientales para comprobarlos con los datos de los barcos de carnada. Las demás variables ambientales disponibles y seleccionadas para someterlas a pruebas de correlación con las estimaciones de la abundancia del barrilete de barcos cerqueros en el período 1961-1984, y las razones por su selección, son las siguientes: 1) Indice de mezcla por el viento (IMV). El grado de mezcla en las capas superiores del océano es proporcional al cubo de la velocidad del viento, llamado IMV. Es posible que el grado de mezcla en las zonas de desove del Pacífico central y occidental afecte la concentración de los organismos que alimentan a las larvas del barrilete, afectando así la supervivencia de éstas, y finalmente determinando el tamaño de las cohortes y el número de reclutas a la pesquería del OPO. 2) TSM en la zona de pesca al realizarse la pesca (TSM). Se ha mostrado que la relación de la CPUE del atún aleta amarilla a la TSM en la zona de pesca es inversa, y existen indicaciones que la CPUE de barrilete es inferior durante eventos del Niño, cuando las TSM son superiores a lo normal. 3) Gradiente norte-sur de las TSM a través del frente térmico frente al Golfo de Guayaquil. Esto es una medida del grado de afloramiento y enriquecimiento nutritivo del nivel superior de las aguas al sur de dicho frente, y finalmente de la producción de alimento para los atunes. 4) La velocidad de la Contracorriente Ecuatorial del Norte (CCEN). Es posible que los bariletes juveniles migren del Pacífico central al Pacífico oriental en la CCEN, que fluye hacia el este; de ser así, es posible que la cantidad de reclutas se vea afectada por variaciones en la velocidad de la corriente. El logaritmo de la tasa anual de captura de reclutas de barrilete por cerqueros de varias banderas en el OPO en el período 1961-1964 estuvo correlacionado de forma positiva con las TSM en la zona de desove del Pacífico central de 18meses antes (r2 0.21),y de forma inversa con el IMV de la zona de desove de 18 meses antes (r2 0.46). El logaritmo de la CPUE de los cerqueros en la zona frente al Golfo de Guayaquil no estuvo correlacionado con las TSM en la zona de desove de 18 meses antes, pero sí estuvo correlacionado de forma inversa con el IMV en la zona de desove de 18 meses antes (r2 0.19),y con el gradiente norte-sur de las TSM en la zona de pesca al realizarse la pesca (r2 0.32). Ninguna de estas estimaciones de abundancia aparente provenientes de barcos cerqueros estuvo correlacionada con las TSM en las zonas de pesca o con la velocidad de la CCEN en épocas anteriores. (PDF contains 140 pages.)