Thermocline topography, horizontal currents and “ridging” in the Eastern Tropical Pacific

ENGLISH: A primary objective of the Inter-American Tropical Tuna Commission is a knowledge of the ecology of tunas which inhabit the Eastern Tropical Pacific. This paper presents some results of the work in physical oceanography, which, it is hoped, will be useful to the biological work and at the same time of interest to physical oceanographers. The work presented here was begun in connection with simple observable facts; the thermocline is very close to the sea surface in a region off Costa Rica (Wooster and Cromwell, 1958), and this region is biologically productive (Holmes, et al. 1957; Brandhorst, 1958). It is the main object of this study to describe and explain these facts, insofar as possible. SPANISH: Uno de los principales objetivos de la Comisión Interamericana del Atún Tropical es el conocimiento de la ecología de los atunes que viven en el Pacífico Oriental Tropical. Este informe presenta algunos de los resultados del estudio en oceanografía física, los cuales se espera que serán útiles en la investigación biológica y, al mismo tiempo, de interés para los oceanógrafos físicos. El trabajo presentado aquí se inició en conexión con sencillos hechos observables; mar afuera de Costa Rica, la termoclina queda muy cerca de la superficie del mar (Wooster y Cromwell, 1958) y esta región es biológicamente productiva (Holmes, el al., 1957; Brandhorst, 1958). El objeto principal de este estudio es describir y explicar estos hechos, hasta donde sea posible. (PDF contains 32 pages.)

A review of the population structure of yellowfin tuna, Thunnus albacares, in the Eastern Pacific Ocean

ENGLISH: Since its inception in 1950 by agreement between the Republic of Costa Rica and the United States of America, the Inter-American Tropical Tuna Commission has been engaged in studies of the biology, ecology and population dynamics of yellowfin tuna in the eastern Pacific Ocean. Prime consideration has been given to the evaluation of the effects of fishing pressure on the yellowfin tuna in this area in order to estimate the maximum sustainable yield. A portion of the eastern Pacific has been defined by the Inter-American Tropical Tuna Commission (1963) as a regulatory area for yellowfin tuna (Figure 1). SPANISH: Desde su incepción en 1950, por un acuerdo entre la República de Costa Rica y los Estados Unidos de América, la Comisión Interamericana del Atún Tropical ha estado ocupada en los estudios de la biología, ecología y dinámica de las poblaciones del atún aleta amarilla en el Océano Pacífico Oriental. Se consideró primariamente la evaluación de los efectos de la presión de la pesquería sobre el atún aleta amarilla en esta área, para poder estimar el rendimiento máximo sostenible. Una parte del Pacífico Oriental ha sido definida por la Comisión Interamericana del Atún Tropical (1963), como área de reglamentación del atún aleta amarilla (Figura 1). (PDF contains 60 pages.)

On the climatology, oceanography and fisheries of the Panama Bight

ENGLISH: Seasonal changes in the climatology, oceanography and fisheries of the Panama Bight are determined mainly by the latitudinal movements of the ITCZ over the region. Evaporation is about 980 mm annually. Rainfall is probably much less than previous estimates because of a discontinuity in the ITCZ. Freshwater runoff from the northern watershed varies from 22 X 109 m3/mo in October-November to 11 X 109 m3/mo in February-March; from the southeastern watershed it varies from 16 X 109 m3/mo in April-June to 9 X 109 m3/mo in October-December. Total annual runoff is about 350 X 109m3. A marked salinity front is found at all seasons off the eastern shore. In the northern part of the Bight temperatures in the upper layers remained fairly constant from May to November; by February the mean temperature had decreased by 4°C and sharp gradients existed in the geographic distributions. Salinities in the upper layers decreased steadily from May to November; by February the mean salinity had increased by 2.5‰. The mean depth of the mixed layer increased from 27 m in May to 40 m in November; by February upwelling decreased it to 18 m. Between November and February upwelling had doubled the amount of P04-P and tripled that of NO3-N in the euphotic zone; surface phytoplankton production and standing crop, and zooplankton concentrations also doubled during this period. Upwelling was about 1.5 m/mo during May-November and about 9.0 m/mo during November-February, the annual total is about 48 m, Mean primary production is about 0.3 gC/m2day during May-December and about 0.6 gC/m2day during January-April; annual production is about 140 gC/m2. A thermal ridge occurred in February running from the northern to the southwestern part of the Bight. Within this ridge was a marked thermal dome coinciding with the center of the cyclonic circulation cell. Upwelling in the dome averaged 16 m/mo in November-February. The fisheries of the Panama Bight annually produce about 30,000 metric tons of food species and about 68,000 m.t. of species used for reduction. Most attempts to further the understanding of tuna ecology were unsuccessful. The apparent abundances of yellowfin and skipjack in the northern part of the Bight appear to be related to the seasonal cycle of upwelling and enrichment, as abundances are greatest in April and May when food appears to be plentiful. The life-cycle of the anchoveta in the Gulf of Panama also appears to be related to upwelling; the species mass varies from about 39,000 m.t. in December to about 169,000 m.t, in April. About 19.1 X 1012 anchoveta eggs are spawned annually. The life-cycles of shrimp in the Panama Bight appear to be related to upwelling as catches are greatest in May-July, about 3-5 months after peak upwelling, and annual catches are inversely correlated with sea level. SPANISH: Los cambios estacionales en la climatología, oceanografía y pesquerías del Panamá Bight están determinados principalmente por el movimiento latitudinal sobre la región de la Zona de Convergencia Intertropical (ZCIT). La evaporación es de unos 980 mm al año. La pluviosidad es probablemente muy inferior a las estimaciones previas a causa de la descontinuidad en la ZCIT. El drenaje de agua dulce, de la vertiente septentrional, varía de 22 x 109m3/mes en octubre-noviembre hasta 11 x 109m3/mes en febreromarzo; el de la vertiente sudeste varía de 16 x 109m3/mes en abril-junio a 9 x 109m3/mes en octubre-diciembre. El drenaje total, anual, es alrededor de 350 x 109m3. En todas las estaciones frente al litoral oriental se encuentra un frente de salinidad marcada. En la parte septentrional del Bight las temperaturas en las capas superiores permanecieron más bien constantes de mayo a noviembre; en febrero la temperatura media había disminuido en unos 4°C y existieron gradientes agudos en las distribuciones geográficas. Las salinidades en las capas superiores disminuyeron constantemente de mayo a noviembre; en febrero la salinidad media había aumentado en 2.5‰. La profundidad media de la capa mixta aumentó de 27 m en mayo a 40 m en noviembre; en febrero el afloramiento disminuyó el espesor de la capa mixta hasta 18 m. Entre noviembre y febrero el afloramiento había duplicado la cantidad de PO4-P y triplicado la de NO3-N en la zona eufótica; la producción superficial de fitoplancton y la biomasa primaria y las concentraciones de zooplancton también se duplicaron durante este período. El afloramiento era cerca de 1.5 mimes durante mayo-noviembre y de unos 9.0 mimes durante noviembre-febrero, el total anual es de unos 48 m. La producción media primaria es aproximadamente de 0.3 gC/m2 al día durante mayo-diciembre y cerca de 0.6 gC/m2 al día durante enero-abril; la producción anual es de unos 140 gC/m2. En febrero apareció una convexidad termal que se extendió de la parte norte a la parte sudoeste del Bight. Dentro de esta convexidad se encontró un domo termal marcado el cual coincidió con el centro de la circulación ciclonal de la célula. El afloramiento en el domo tuvo un promedio de 16 mimes en noviembre-febrero. Las pesquerías del Panamá Bight producen anualmente de cerca 30,000 toneladas métricas de especies alimenticias y unas 68,000 t.m. de especies usadas para la reducción. La mayoría de los esfuerzos realizados con el fin de adquirir más conocimiento sobre la ecología del atún no tuvo éxito. La abundancia aparente del atún aleta amarilla y del barrilete en la parte septentrional del Bight parece estar relacionada con el ciclo estacional del afloramiento y del enriquecimiento, ya que la abundancia mayor en abril y mayo cuando parece que hay abundancia es de alimento. El ciclo de vida de la anchoveta en el Golfo de Panamá parece también que está relacionada al afloramiento. La masa de la especie varía de unas 39,000 t.m. en diciembre a cerca de 169,000 t.m. en abril. Aproximadamente 19.1 x 1012 huevos de anchoveta son desovados anualmente. Los ciclos de vida del camarón en el Panamá Bight parecen estar relacionados con el afloramiento ya que las capturas son superiores en mayo-julio, unos 3-5 meses después del ápice del afloramiento, y las capturas anuales se correlacionan inversamente con el nivel del mar. (PDF contains 340 pages.)

Oceanographic observations in the Gulf of Guayaquil, 1962-1964. Part II. Biological, chemical and physical.

ENGLISH: During 1961 the government of Ecuador, with the financial assistance of the Special Fund of the United Nations and the technical assistance of FAO experts, initiated an extensive program of fisheries research centered in a fisheries institute established in Guayaquil. In cooperation with this program, and in connection with Ecuador's adherence in 1961 to the Convention for the Establishment of an Inter-American Tropical Tuna Commission, a two-and-a-half year investigation of the ecology of the Gulf of Guayaquil and adjacent waters was started by the Inter-American Tropical Tuna Commission. SPANISH: Durante 1961 el gobierno ecuatoriano con el apoyo financiero del Fondo Especial de las Naciones Unidas y la ayuda técnica de los expertos de la FAO, inició un programa extensivo de investigación pesquera, centralizado en el instituto pesquero establecido en Guayaquil. En cooperación con este programa y en conexión a la afiliaci6n del Ecuador a la Convención, en 1961, para el establecimiento de una Comisión Interamericana del Atún Tropical, Cue iniciada por la Comisión una investigación de dos aftos y medio sobre la ecología del Golfo de Guayaquil y de las aguas adyacentes. (PDF contains 501 pages.)

Report of the Inter-American Tropical Tuna Commission for the year 1962

ENGLISH: The Inter-American Tropical Tuna Commission, pursuant to the provisions of the Convention, has the duty of collecting and interpreting factual information to facilitate maintaining the populations of tunas, and of tuna baitfishes, supporting the fisheries pursued by nationals of its Member Governments in the Eastern Pacific Ocean, at levels which will permit maximum sustainable average harvests year after year. This requires a wide variety of research into the biology, life history, ecology and population dynamics of the several species, and investigations into the effects of both natural factors and fishing activity on their abundance and on the harvests they can sustain. The research is conducted by a permanent, internationally recruited scientific staff, employed directly by the Commission, selected on the basis of professional competence by the Director of Investigations. SPANISH: La Comisión Interan1ericana del Atún Tropical, de informidad con las disposiciones de la Convención, tiene el deber de recolectar e interpretar la información que facilite el mantenimiento de las poblaciones del atún y de los peces de carnada que sirven para la pesca de este, sosteniendo las pesquerías a que se dedican los habitantes de sus Gobiernos Miembros en el Océano Pacifico Oriental, a niveles ,de abundancia que permitan un promedio máximo sostenible de cosechas ano tras ano. Esto requiere una amplia variedad de investigaciones dentro de la biología, historia natural, ecología y dinámica de las poblaciones de diversas especies, y sabre los efectos, tanto de los factores naturales como de la actividad pesquera, en la abundancia de las mismas y en el rendimiento que puedan dar. La investigación es conducida por un grupo científico permanente, cuyos miembros son reclutados internacionalmente empleados directamente por la Comisión, una vez que han sido seleccionados sobre la base de su competencia profesional, por el Director de Investigaciones. (PDF contains 149 pages.)

Economic analysis of fish farming in Ogun State

This study examined the economic potential of fish farming in Abeokuta zone of Ogun State in the 2003 production season. Descriptive statistics cost returns and multiple regression analysis were used in analyzing the data. The farmers predominantly practiced monoculture. Inefficiency in the use of pond size, lime and labour with over-utilization of fingerlings stocked was revealed by the study. The average variable cost of N124.67 constituted 45% of the total while average fixed cost was N149.802.67 per average farm size. Fish farming was found to be a profitable venture in the study area with a net income of N761, 400.58 for an average pond size of 301.47sq.m. Based on these findings, it is suggested that for profit maximization, the fish farm will have to increase the level of their use of fingerlings and fertilizers and decrease the use of lime labour and pond size

News from Academy Bay

Ecología de los Chivos Ferales (Capra hircus) en el Volcán Alcedo. Ecology of Feral Goats (Capra hircus) on Alcedo Volcano. Pepino War, 1992.

Using the empirical Bayes method to estimate and evaluate bycatch rates of seabirds from individual fishing vessels

Minimizing bycatch of seabirds is a major goal of the U.S. National Marine Fisheries Service. In Alaska waters, the bycatch (i.e., inadvertent catches) of seabirds has been an incidental result of demersal groundfish longline fishery operations. Notably, the endangered short-tailed albatross (Phoebastria albatrus) has been taken in this groundfish fishery. Bycatch rates of seabirds from individual vessels may be of particular interest because vessels with high bycatch rates may not be functioning effectively with seabird avoidance gears, and there may be a need for suggestions on how to use these avoidance gears more effectively. Therefore, bycatch estimates are usually made on an individual vessel basis and then summed to obtain the total estimate for the entire fleet.

The California Red Sea Urchin, Strongylocentrotus franciscanus, Fishery: Catch, Effort, and Management Trends

California's red sea urchin, Strongylocentrotus franciscanus, catch peaked at 23,577 metric tons (t) in 1988. Since then, catches and CPUE have trended downward at different rates in northern and southern California, with 10,086 t landed statewide in 1995. West coast sea urchin catches and CPUE from British Columbia, Can., to Baja California, Mex., have generally declined during this period which followed a decade of rapid fishery expansion. This expansion was in response to increasing demand from Japan fueled by rising prices based largely on a more favorable export currency exchange rate. West coast stock assessment methods have been based on integrating a combination of fisheries dependent data and population surveys into models at various levels of complexity. California management policy has centered on technical measures such as size limits and seasonal closures and has been largely ineffective in stabilizing declining catches.

Feeding Ecology of the Franciscana (Pontoporia blainvillei) In Marine And Estuarine Waters Of Argentina

Stomach contents of 110 franciscanas (Pontoporia blainvillei), from northern Argentina were analysed in order to improve our knowledge about the feeding habits of this species and to better characterise the lactation period. The samples included calves, juveniles and adults of both sexes. Evidence of predation by franciscanas is seen at a very young age (2.5-3 months), with a transition diet composed by both milk and solid food, mainly represented by crustaceans. Weaning seems to begin by April, when franciscanas are about 6-7 months old. Franciscanas inhabiting two different habitats were analysed in this study: a brackish water estuary and an adjacent marine coastal system. The diet of Pontoporia blainvillei in northern Argentina was composed by a total of 26 prey species: 20 teleosts, 4 crustaceans and 2 cephalopods. Based on the Index of Relative Importance (IRI) the main prey species were Cynoscion guatucupa, Micropogonias furnieri, Loligo sanpaulensis and Urophycis brasiliensis. Estuarine franciscanas preyed mainly on Micropogonias furnieri (dominant species), Cynoscion guatucupa, Odonthestes argentinensis and Macrodon ancylodon, while dolphins from marine areas preyed mainly on Cynoscion guatucupa (dominant species), Loligo sanpaulensis and Urophycis brasiliensis. Our results confirm that franciscanas prey mainly on juvenile fish (< 8cm) and small loliginid squids, in close agreement with previous results obtained in southern Brazil and Uruguay. Qualitative and quantitative differences observed in the diet of dolphins from each habitat emphasise the need to discriminate between samples from different habitats and environmental parameters. SPANISH: Se analizaron 110 contenidos estomacales de franciscanas (Pontoporia blainvillei) provenientes de la costa norte de Argentina, para extender en conocimiento sobre su dieta y caracterizar la lactancia. Las muestras incluyeron cachorros, juveniles y adultos de ambos sexos. Las primeras etapas de predación se inician a muy temprana edad (2,5-3 meses), presentando una dieta de transición compuesta tanto por leche como por presas sólidas, principalmente crustáceos; el destete se iniciaría a partir de abril, a una edad estimada entre 6 y 7 meses. Las franciscanas estudiadas provienen de dos habitats diferentes: un área estuarial de baja salinidad y la region marina adyacente. La dieta de Pontoporia blainvillei de Argentina estuvo compuesta por un total de 26 especies: 20 teleósteos, 4 crustáceos y 2 cefalópodos. Basados en el Indice de Importancia Relativa (IIR), las presas más importantes fueron Cynoscion guatucupa, Micropogonias furnieri, Loligo sanpaulensis y Urophycis brasiliensis. Las franciscanas provenientes del área estuarial predaron principalmente sobre Micropogonias furnieri (especie dominante), Cynoscion guatucupa, Odonthestes argentinensis y Macrodon ancylodon, mientras que los delfines marinos predaron sobre Cynoscion guatucupa (especie dominante), Loligo sanpaulensis y Urophycis brasiliensis. Nuestros resultados confirman que la franciscana preda sobre peces juveniles (< 8cm) y pequeños calamares Loliginidae, coincidiendo con resultados previos obtenidos en el sur del Brasil y Uruguay. Las diferencias cualitativas y cuantitativas observadas en la dieta de cada uno de las áreas analizadas, nos sugieren que los futuros estudios sobre ecología trófica de la franciscana deberían discriminarse de acuerdo al origen de los ejemplares y a la tipificación del ambiente.

Socioeconomic conditions of traditional fishermen of Vitava village in Thane district

Maharashtra stands third in fish production in India, with an estimated annual landings of 3.32 lakhs tonnes (1986-87). About 45% of the fishermen are directly involved in fishing. Mechanisation has boosted fish production resulting in gainful employment and higher incomes to fishermen. However, traditional fishermen along Thane creek and who entirely depend on fishing for their livelihood are comparatively poor due to their dependence on subsistence fishing and reduction of fish stock due to pollution of the creek. Conservation of the resources, proper monitoring of pollution and financial assistance and guidance will help the fishermen improve their living conditions.