Biological production in the Eastern Pacific Ocean

ENGLISH:The present paper is principally concerned with the geographic distribution of the standing crop and production of phytoplankton at the surface of the eastern Pacific, east of 130°W and between 10°N and 33°S, as reflected by recently collected data. In addition we discuss some of the more obvious, general relationships among thermocline topography, nutrient concentration, and the various trophic levels from primary production to fish production. The limited data do not allow a seasonal study. We have therefore mapped all of the data together regardless of the time of collection, but do not wish to imply that the physical, chemical and biological system is without seasonal or periodic change. SPANISH:Como lo reflejan los datos recientemente recolectados, el presente trabajo está dedicado principalmente a la distribución geográfica de las cosechas estables y a la producción del fitoplancton en la superficie del Pacífico Oriental, al este de los 130°W y entre los 10°N y 33°S. Además discutimos algunas de las relaciones generales más obvias entre la topografía de la termoclina, la concentración de los nutrientes, y los varios niveles tróficos, desde la producción primaria hasta la producción de los peces. Los datos limitados no permiten un estudio estacional. Por lo tanto, hemos combinado todos los datos no tomando en cuenta el tiempo de la recolección, pero no queremos implicar que no existen cambios estacionales o periódicos en el sistema físico, químico y biológico.

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.

Changes in the size structure of the yellowfin tuna population of the tropical eastern Pacific Ocean from 1947 to 1955

ENGLISH: Morphometric studies by Godsil (1948), Godsil and Greenhood (1951), Royce (1953) and Schaefer (1952, 1955) have indicated that the yellowfin tuna of the Eastern Pacific are distinct from those of the Central Pacific. Tagging of yellowfin tuna by the California Department of Fish and Game, and by the Inter-American Tropical Tuna Commission in the Eastern Pacific, and by the Pacific Oceanic Fishery Investigations in the Central Pacific, have not yet revealed any migrations between these areas. Shimada and Schaefer (1956) have compared changes in population abundance and fishing intensity, considering the population in the Eastern Pacific as a separate entity. They conclude " ... the amount of fishing has had a real effect upon the stock of Eastern Pacific yellowfin tuna, taken in the aggregate, over the period studied. The evidence suggests also that for this species the intensity of fishing in some recent years has reached and might have even exceeded the level corresponding to the maximum equilibrium yield." Tagging experiments by the California Department of Fish and Game and by the Inter-American Tropical Tuna Commission have yielded returns in the order of one to five percent (Roedel 1954, and unpublished data of both agencies), a level much lower than that at which fishing intensity would be expected to noticeably affect the population size. These results are probably a reflection of the inadequacies of the present tagging methods, but they could lend doubt to the conclusions of Shimada and Schaefer. It is desirable, therefore, to examine other, independent, evidence as to the effects of fishing on the population. At the high levels of fishing intensity suggested by Shimada and Schaefer, in addition to changes in quantity, measurable changes would be expected to have occurred in the quality of the yellowfin tuna stocks, because the average age and size of the fish would have been reduced by the high mortality rates accompanying high fishing intensities. A continuing regular program of sampling catches and determining their length composition, to assess changes in the size composition of the stocks, was initiated by the Commission in 1954 but direct measurements are not available for the earlier, more dynamic period of growth of the fishery. Consequently, other, more general indications of possible changes in the size composition were sought. SPANISH: Los estudios morfométricos efectudos por Godsil (1948), Godsil y Greenhood (1951), Royce (1953) y Schaefer (1952, 1955), han demostrado que el atún aleta amarilla del Pacífico Oriental es distinto del que habita el PacÍfico Central. Los experimentos del Departamento de Pesca y Caza de California y de la Comisión Interamericana del Atún Tropical en el Pacífico Oriental, así como los de las Investigaciones Pesqueras del Océano Pacífico en el Pacífico Central,consistentes en la marcación de atunes aleta amarilla, aún no han puesto de manifiesto movimientos migratorios entre dichas áreas. Shimada y Schaefer (1956) han hecho estudios comparativos sobre la abundancia de la población y la intensidad de la pesca, considerando a la población del Pacífico Oriental como una entidad separada. Su conclusión es que " ... la intensidad de la pesca ha tenido un definido efecto sobre la población del atún aleta amarilla del Pacífico Oriental, tomada en conjunto, a lo largo del período estudiado. La evidencia de que se dispone sugiere así mismo que, por lo que hace a esta especie, la intensidad de la pesca en los últimos años ha alcanzado y quizás aún sobrepasado el nivel correspondiente a la máxima pesca de equilibrio". Los experimentos de mar•cación del Departamento de Pesca y Caza de California y de la Comisión Interamericana del Atún Tropical han producido recuperaciones ,entre el uno y el cinco por ciento (Roedel 1954 y datos inéditos de ambos organismos), lo que constituye un nivel mucho más bajo de aquél en que la intensidad de la pesca podría considerarse que afectaría notablemente el tamaño de la población. Estos resultados reflejan probablemente lo inadecuados que son aún los métodos de marcación, pero ellos podrían, quizá, poner en tela de juicio las conclusiones de Shimada y Schaefer. Por lo tanto,es deseable examinar otras fuentes de evidencia independientes, relacionadas con el efecto que la pesca tiene sobre la población. En efecto, si los altos índices de pesca sugeridos por Shimada y Schaefer son correctos, es de esperar que, además de los cambios en la magnitud de la población, se hayan producido otros, concomitantes y sensibles, en la calidad de los stocks de atún aleta amarilla, puesto que tanto el promedio de edad como el de tamaño de los individuos habrían disminuído debido a las elevadas tasas de mortalidad inherentes a las altas intensidades de pesca. En 1954 la Comisión inició un programa ininterrumpido para tomar muestras y determinar en ellas las frecuencias de tallas y evaluar de este modo los cambios correlativos que tuvieran lugar en los stocks pero, infortunadamente, este sistema de evaluación directa no fué practicado en el período anterior, que fué precisamente el de rápida expansión de la pesquería. En tal virtud, hubo de ser necesario buscar indicios más generales referentes a los cambios posibles en la composición de tamaños. (PDF contains 20 pages.)

A study of the Eastern Pacific fishery for tuna baitfishes, with particular reference to the anchoveta (Cetengraulis mysticetus)

ENGLISH: Most of the catches of yellowfin and skipjack tuna from the Eastern Pacific Ocean are made by vessels fishing with poles and lines and live bait. From 1931 to 1954, these baitboats, on the average, accounted for over three-fourths of the total annual California landings of yellowfin and skipjack (Shimada and Schaefer, 1956). With the substantial increase in recent years in the production of the tropical tunas, there have been greater demands for live bait. This increased need for larger amounts of baitfishes has given rise to important questions relating to the manner in which these populations may be most wisely used. The Inter-American Tropical Tuna Commission has been concerned with various aspects of this problem since its establishment in 1950. This report presents some of the results obtained from the Commission's studies of the baitfishes important to the fishery for yellowfin and skipjack tuna. It traces briefly the origin and development of the bait fishery, describes its operations, extent, and yield, and discusses some aspects of the effects of exploitation upon the Eastern Pacific baitfish populations, particularly of the anchoveta (Cetengaulis mysticetus). SPANISH: Los barcos que emplean cañas y cuerdas y carnada viva, son los que realizan la mayor parte de la pesca de atún aleta amarilla y barrilete en el Océano Pacifíco Oriental. De 1931 a 1954 estos barcos han desembarcado, en promedio, más de las tres cuartas partes de las pescas anuales de ambas especies (Shimada y Schaefer, 1956). Con el aumento sustancial en dicha producción en los últimos años, ha habido una mayor demanda por carnada viva. Esta creciente necesidad de obtener cantidades mayores de pecescebo, ha originado importantes cuestiones relativas a la mejor forma en que estas poblaciones pueden ser utilizadas. A la Comisión Interamericana del Atún Tropical le ha tocado ocuparse de varios aspectos de este problema, desde que fué establecida en el año 1950. Este informe ofrece algunos de los resultados obtenidos a través de los estudios de la Comisión sobre los peces-cebo importantes para la pesquería de atún aleta amarilla y barrilete; señala brevemente el origen y desarrollo de la pesquería de carnada; describe sus operaciones, extensión y rendimiento, y trata algunos aspectos de los efectos de la explotación sobre las poblaciones de dichos peces en el Pacifíco Oriental, particularmente de la anchoveta (Cetengraulis mysticetus). (PDF contains 59 pages.)

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

ENGLISH: These aspects of the schooling habits of the yellowfin and skipjack tuna may be investigated by means of the logbook records of the catches 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 school sizes based on these data requires the additional assumption either that the entire school is captured or that each set captures a constant fraction of the school upon which it is made. In this paper we report on the results of such investigations based on logbook records of the purse-seine fleet. SPANISH: Estos aspectos de los hábitos gregarios de los atunes aleta amarilla y barrilete pueden ser investigados a base de los registros de bitácora en que se anotan las pescas resultantes de cada una de las operaciones con la red de encierre que realizan los barcos rederos. Para ambos propósitos hay que suponer que las operaciones se efectúan, en cada caso, en un cardumen independiente. El estudio de los tamaños de los cardúmenes o manchas, a base de estos datos, requiere una suposición adicional: que el cardumen entero es capturado o, en su defecto, que en cada operación con la red se pesca una fracción constante de la mancha objeto de la pesca. En el presente artículo damos cuenta de los resultados de dichas investigaciones basadas en los registros de bitácora que lleva la flota de embarcaciones que utilizan redes de encierre. (PDF contains 47 pages.)

Primary production, chlorophyll, and zooplankton volumes in the tropical Eastern Pacific Ocean

ENGLISH: Between 1 October and 17 December 1955 investigations of the physical, chemical and biological oceanography of the Eastern Pacific Ocean in a region bounded approximately by 30° N. latitude, 9° S. latitude, 120° W. longitude and the mainland coast were conducted from the vessels Horizon and Spencer F. Baird of the Scripps Institution of Oceanography of the University of California. These were part of a cooperative operation, designated for convenience by the code name "Eastropic," in which a vessel of the U. S. Fish and Wildlife Service worked, during this same period, further west and a vessel of the Peruvian Navy worked further south, offshore from Peru. A vessel of the California State Fisheries Laboratory also conducted certain sub-surface tuna fishing operations and other studies in the same general region as the Scripps vessels. In addition to carrying out a number of special studies related to particular oceanographic features, the Scripps vessels occupied a considerable number of hydrographic stations. The locations of these stations, at each of which were made net-hauls for zooplankton, are shown in Figure 4 and Tables 2 and 3. At some of the hydrographic stations, and in Some places between stations, there were made from the Spencer F. Baird measurements of chlorophyll "a" and of primary production (by the C14 technique), both in situ and in a shipboard incubator. The purpose of this paper is to report on the results of these biological observations. SPANISH: Entre el 1° de octubre y el 17 de diciembre de 1955, a bordo de los barcos Horizon y Spencer F. Baird) de la Institución Scripps de Oceanografía de la Universidad de California, se hicieron investigaciones sobre la oceanografía física, química y biológica del Océano Pacífico Oriental, en una región limitada aproximadamente por los 30° N. de latitud, 9° S. de latitud, 120° O. de longitud y la costa continental. Estas investigaciones fueron parte de una operación que se realizó cooperativamente y a la que se convino darle el nombre codificado de "Eastropic". En ella, durante el mismo período, una embarcación del Servicio de Pesca y Vida Silvestre de los Estados Unidos (U. S. Fish and Wildlife Service) trabajó más hacia el oeste, y un barco de la armada peruana más hacia el sur, frente a la costa del Perú. También colaboró una nave del Laboratorio de Pesquerías del Estado de California (California State Fisheries Laboratory), realizando algunas operaciones de pesca de atún en aguas subsuperficiales, y otros estudios en la misma región general que recorrieron las embarcaciones de Scripps. Además de efectuar estudios especiales relacionados con las caracteristicas oceanográficas particulares de la región, las naves de Scripps establecieron un buen número de estaciones hidrográficas. La localización de estas estaciones se indica en la Figura 4 y en las Tablas 2 y 3; en cada una de ellas se hicieron rastreos con redes planctónicas para recoger muestras de zooplancton. En algunas de las estaciones hidrográficas, así como en algunos lugares entre estaciones, en el Spencer F. Baird se hicieron mediciones de la clorofila "a" y de la producción primaria (mediante la técnica del C14), tanto in situ como en una incubadora instalada a bordo. El propósito del presente trabajo es dar a conocer los resultados de estas observaciones biológicas. (PDF contains 44 pages.)

Marine Flora and Fauna of the eastern United States: Acanthocephala

The phylum Acanthocephala (intestinal worm parasites of vertebrates) of the Atlantic coast of the United States comprises 43 species and 20 genera belonging to three orders: Echinorhynchida, Neoechinorhynchida, and Polymorphida. Adults are exclusively intestinal parasites of vertebrates. This study includes those species found in vertebrates of marine and estuarine environments along the North American Atlantic coast between Maine and Texas. Species that can be found within that geographical range and those that typically infect freshwater fishes but that are occasionally present in marine or estuarine hosts are also included. The taxonamy, anatomy, natural history, and ecology of the phylum Acanthocephala are discussed, and an illustrated key to the genera is presented. Techniques, an annotated systematic treatment of all 43 species, and a systematic index are included. No systematic decisions will be made at this time, but areas where such decisions are pending will be indicated and discussed for future reports. (PDF file contains 32 pages.)

Marine Flora and Fauna of the Eastern United States: Platyhelminthes: Monogenea

(PDF file contains 112 pages.)

Stocks of Dolphins (Stenella spp. and Delphinus delphis) in the Eastern Tropical Pacific: A Phylogeographic Classification

Current information is reviewed that provides clues to the intraspecific structure of dolphin species incidently killed in the yellowfin tuna purse-seine fishery of the eastern tropical Pacific (ETP). Current law requires that management efforts are focused on the intraspecific level, attempting to preserve local and presumably locally adapted populations. Four species are reviewed: pantropical spotted, Stenella attenuata; spinner, S. longirostTis; striped, S. coeruleoalba; and common, Delphinus delphis, dolphins. For each species, distributional, demographic, phenotypic, and genotypic data are summarized, and the putative stocks are categorized based on four hierarchal phylogeographic criteria relative to their probability of being evolutionarily significant units. For spotted dolphins, the morphological similarity of animals from the south and the west argues that stock designations (and boundaries) be changed from the current northern offshore and southern offshore to northeastern offshore and a combined western and southern offshore. For the striped dolphin, we find little reason to continue the present division into geographical stocks. For common dolphins, we reiterate an earlier recommendation that the long-beaked form (Baja neritic) and the northern short-beaked form be managed separately; recent morphological and genetic work provides evidence that they are probably separate species. Finally, we note that the stock structure of ETP spinner dolphins is complex, with the whitebelly form exhibiting characteristics of a hybrid swarm between the eastern and pantropical subspecies. There is little morphological basis at present for division of the whitebelly spinner dolphin into northern and southern stocks. However, we recommend continued separate management of the pooled whitebelly forms, despite their hybrid/intergrade status. Steps should be taken to ensure that management practices do not reduce the abundance of eastern relative to whitebelly spinner dolphins. To do so may lead to increased invasion of the eastern's stock range and possible replacement of the eastern spinner dolphin genome.(PDF file contains 24 pages.)

Structure and Historical Changes in the Groundfish Complex of the Eastern Bering Sea

The eastern Bering Sea is a major marine ecosystem containing some of the largest populations of groundfish, crabs, birds, and marine mammals in the world. Commercial catches of groundfish in this region have averaged about 1.6 million tons (t) annually in 1970-86. This report describes the species and relative importance of species in the eastern Bering Sea groundfish complex, the environment in which they live, and the history of the fisheries and management during the years 1954 - 1985. Historical changes in abundance and the condition of the principal species at the end of this first 30 years of exploitation are also examined. Results suggest that the biomass of the groundfish complex is characterized by variability rather than stability. The most reliable data (1979 to 1985) suggests that the biomass of the complex fluctuated between 11.8 and 15.7 million t. Even greater variability is suggested by the less reliable data from earlier years. Because of its dominance in the complex and wide fluctuations in abundance, walleye pollock (Theragra chalcogramma) is primarily responsible for the major variations in abundance of the complex. After 30 years of exploitation, the complex was generally in excellent condition. (PDF file contains 100 pages.)

Seasonal Climatologies and Variability of Eastern Tropical Pacific Surface Waters

Interannual variability caused by the El Nino-Southern Oscillation in the eastern tropical Pacific Ocean (ETP) is analogous to seasonal variability of comparable magnitude. Climatological spatial patterns and seasonal variability of physical variables that may affect the ETP ecosystem are presented and discussed. Surface temperature, surface salinity, mixed layer depth, thermocline depth, thermocline strength, and surface dynamic height were derived from bathythermograph, hydrocast, and CTD data. Surface current velocity, divergence, and upwelling velocity were derived from ship drift reports. Surface wind velocity, wind stress, wind divergence, wind stress curl, and Ekman pumping velocity were derived from gridded pseudostress data obtained from Florida State University. Seasonal maps of these variables, and their deviations from the annual mean, show different patterns of variation in Equatorial (S°S-SON) and Tropical Surface Water (SOlS0N). Seasonal shifts in the trade winds, which affect the strength of equatorial upwelling and the North Equatorial Countercurrent, cause seasonal variations in most variables. Seasonal and interannual variability of surface temperature, mixed layer depth, thermocline depth and wind stress were quantified. Surface temperature, mixed layer depth and thermocline depth, but not local wind stress, are less variable in Tropical Surface Water than in Equatorial Surface Water. Seasonal and interannual variability are close to equal in most of the ETP, within factors of 2 or less. (PDF file contains 70 pages.)

Marine Flora and Fauna of the Eastern United States: Dicyemida

This manual treats the six species of dicyemid mesozoans that have been reported in three species of hosts (Octopus vulgaris, O. joubini, and O. briareus) from the eastern coast of North America and the Gulf of Mexico, including the Florida Keys. All are parasites of species of Octopus and are in the genus Dicyema, family Dicyemidae. In the introduction, the life cycle, as known, and the general morphology of dicyemids are briefly described, and methods are given for collecting and preparing material for study. These are followed by a key to species and by an annotated checklist, which includes data, some hitherto unpublished, on their known prevalence in hosts from various localities including Bimini and Bermuda.(PDF file contains 20 pages.)

Marine Flora and Fauna of the Eastern United States: Copepoda, Cyclopoida: Archinotodelphyidae, Notodelphyidae, and Ascidicolidae

This manual includes an introduction to the general biology, a selected bibliography, and an illustrated key to 11 genera and 17 species of copepods of the Crustacea, Subclass Copepoda, Order Cyclopoida, Families Archinotodelphyidae, Notodelphyidae and Ascidicolidae, associated with ascidians from the Atlantic Coast of the United States. Species distributed from the Gulf of Maine to Long Island Sound are emphasized. An annotated systematic list, with statements of the world distribution and new records of association with hosts, and a systematic index are also provided. (PDF file contains 44 pages.)

Marine flora and fauna of the eastern United States Mollusca: Cephalopoda

The cephalopods found in neritic waters of the northeastern United States include myopsid and oegopsid squids, sepiolid squids, and octopods. A key with diagnostic illustrations is provided to aid in identification of the eleven species common in the neritic waters between Cape Hatteras and Nova Scotia; included also is information on two oceanic species that occur over the continental shelf in this area and that can be confused with similar-looking neritic species. Other sections comprise a glossary of taxonomic characters used for identification of these species, an annotated systematic checklist, and checklists of the 89 other oceanic species and 18 Carolinian and subtropical neritic species that might occur occasionally off the northeastern United States. (PDF file contains 30 pages.)

Greenland turbot Reinhardtius hippoglossoides of the eastern Bering Sea and Aleutian Islands region

Greenland turbot (Reinhardtius hippoglossoides) is a commercially important flounder in both the North Atlantic and North Pacific Oceans. In the latter, its center of abundance is in the eastern Bering Sea and along the Aleutian Islands chain where its population is managed as a single stock. Harvest levels in this region of the North Pacific during the period 1970-81 were comparable with those in the northwest and northeast Atlantic, with annual average catches of 53,000 metric tons (t). However, the catch in 1984 dropped sharply to 23,100 t, in part because of reduced quotas arising from concern over continued poor recruitment and declining catch-per-unit-effort. Recruitment failure was manifested in 1) the sharp decline in the catch rate of young flsh in annual research trawl surveys on the continental shelf of the eastern Bering Sea and 2) an increasing proportion of older and larger fish in the commercial catch from the continental slope of both the eastern Bering Sea and Aleutian Islands. The cause ofthe decline in recruitment could not be clearly identifled. Greenland turbot of the Bering Sea-Aleutian Islands share certain distributional features with the North Atlantic form. There is an apparent bathymetric change in the size and age of fish, with younger animals occupying continental shelf depths and the older individuals residing at depths of the continental slope. At shallow depths the young are exposed to temperature fluctuations, whereas older animals along the slope are exposed to relatively stable temperatures. A hypothesis is proposed for describing the temporal and spatial paths by which young animals reach the mature or spawning portion of the population. (PDF file contains 38 pages.)