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.)

An evaluation of the pelagic primary productivity and potential fish yield of Kainji Lake, Nigeria

The environmental conditions of Kainji Lake from 1971/72 to date appear to have stabilized to a large extent, judging from the similarity of physico-chemical parameters investigated in this study over the period. Solar radiation (as reflected in variation in temperature) and pH have remained largely constant over the years, while conductivity (index of nutrient enrichment), though significantly higher in 1995/96, could be described as sporadic and needs further monitoring to ascertain its trend in the lake. While water transparency and dissolved oxygen were higher in 1971/72 compared to the other years, these increases cannot be said to be overwhelming. The lower transparency in 1995/96 was due to the exceptional flood of that year and may have also accounted for the poorer dissolved oxygen concentration compared to the other years due to its impact on photosynthesis. There is no evidence from this study to indicate that primary productivity has increased over the years. Consequently, the observed increase in fish yield by the KLFPP from CAS, which is corroborated by estimates from the MEI, cannot be supported on the basis of improved photosynthetic production. The phenomenal high levels of conductivity recorded during certain periods in 1995 (600 mu mhos cm super(-1)) are hitherto unknown in the lake and may indicate a trend towards nutrient enrichment. However, it is premature at this stage to conclude on its long-term impact on primary production and consequently, on fish yield. Secondly, the notion of overfishing in the 80s (Ita, 1993), may need to be further examined as low or dwindling catches could be due to a number of factors among which are the level of fishing effort, the type and efficiency of gears and the intensity of sampling. It would appear that with the intervention of KLFPP, the better management of the lake's fisheries would increase the current level of catch. It also needs to be examined how much of the clupeid fisheries, which is now known to account for a substantial proportion of the total fish yield in Kainji Lake, was included in the sampling of the 80s. (PDF contains 43 pages)

Ratio of natural isotopes of nitrogen. I. Primary results: soils of Dombes [Translation from: Revue d'Ecologie et de Biologie du Sol 14, 279-287, 1977]

Utilization of the heavy isotope of nitrogen as a tracer has found numerous applications in soil biology. It allows better definition of different stages of the nitrogen cycle, in particular the immobilization-mineralization cycle. In this work, the authors report the results of calculations of natural isotope ratios of nitrogen in samples of water, soil and vegetation prevailing in Dombes and discuss the possibilities of errors and coefficients of fractionation.

Avian piscivores: basis for policy.

In Britain, many birds eat fish in fresh waters but only three species, cormorant, red-breasted merganser and goosander, are commonly perceived to present serious problems for freshwater fisheries. Complaints are mainly that cormorants eat large fish and that all three bird species eat so many juvenile fish, that there are subsequently fewer fish to be harvested or angled, but also that persistent predation by birds changes fish behaviour so that they are less 'catchable'. To this end, this report reviews existing information on the current status, foraging ecology, and population biology of the three bird species as background to their potential impact on fisheries. Discusses fish population dynamics within the context of predation effects. Reviews existing experimental evidence for impacts on fish populations and fisheries; and describes current legislation, discusses potential criteria for serious damage to a fishery, and suggests ways forward for NRA policy and research.

Is epizootic ulcerative syndrome (EUS) specific fungus of fishes a primary pathogen?: an opinion

Earlier findings on epizootic ulcerative syndrome (EUS) and the present observation of the authors on transmission of EUS to snakehead (Channa sp.) without skin damage provide evidence to suggest that the invasive fungus associated with EUS is a primary pathogen.

Ecology and growth of juvenile California spiny lobster, Panulirus interruptus (Randall)

ABSTRACT TRANSCRIBED FROM ENGLE'S PH.D. ORAL DEFENSE PAMPHLET: The natural history of juvenile California spiny lobster, Panulirus interruptus (Randall), was investigated, with primary emphasis placed on ascertaining juvenile habitats, determining juvenile growth rates and component growth processes, and evaluating ecological and behavioral phenomena associated with juvenile survival and growth. Habitat surveys of island and mainland localities throughout southern and lower California revealed that small, greenish juveniles typically inhabit crevices or temporary burrows in 0-4m deep, wave-swept rocky habitats covered by dense beds of surf grass, Phyllospadix torreyi S. Watson. Phyllospadix beds were more abundant on gradually sloping rocky mainland beaches than on steeply sloping island shores. Phyllospadix abundance was positively correlated with P. interruptus abundance; however, at Santa Catalina Island, the Phyllospadix habitat was not extensive enough to be the sole lobster nursery. In laboratory tests, puerulus larvae and early juveniles chose Phyllospadix over rubble rocks or broad-bladed kelp, but did not consistently prefer Phyllospadix over reticulate algae. Ecology, growth, and behavior of juvenile P. interruptus inhabiting a discrete Phyllospadix habitat at Bird Rock, Santa Catalina Island, were investigated from October 1974 through December 1976 by means of frequent scuba surveys. Pueruli settled from June to November. Peak recruitment occurred from July to September, when seasonal temperatures were maximal. Settled larvae were approximately one year old. Juvenile growth was determined by size-frequency, single molt increment, mark-recapture, and laboratory culture studies. Carapace length vs. wet weight relationships fit standard power curve equations. Bird Rock juveniles grew from 7 to 32mm CL in 10-11 molts and from 32 to 56mm CL in 5-6 molts during their first and second benthic years, respectively. Growth rates were similar for males and females. Juveniles regenerating more than two limbs grew less per molt than intact lobsters. Long-term growth of laboratory-reared juveniles was 20% less than that of field lobsters. Growth component multiple regression analyses demonstrated that molt increment was directly proportional to premolt size and temperature for age 1+ lobsters. Molt frequency was inversely proportional to size and directly proportional to temperature. Temperature affected age 2+ lobsters similarly, but molt increment was independent of size, and molt frequency declined at a different rate. Juvenile growth rates more than doubled during warm water months compared to cold water months, primarily because of increased molt frequency. Based on results from this study and from previous investigations, it is estimated that P. interruptus males and females become sexually mature by ages 4 and 5 years, respectively, and that legai size is reached by 7 or 8 years of age. Juvenile P. interruptus activity patterns and foraging behavior were similar to those of adults, except that juvenile home ranges were proportionally smaller, and small juveniles were apparently not attracted to distant food. Small mollusks, abundant in Phyllospadix habitats, were the major food items. Size-dependent predation by fish and octopus apparently caused the considerable juvenile mortality observed at Bird Rock. Juveniles approaching 2 years of age gathered in mixed size-class aggregations by day and foraged beyond the grass beds at night. In autumn, these juveniles migrated to deeper habitats, coincident with new puerulus settlement in the Phyllospadix beds. Based on strong inferences from the results, it is proposed that size-dependent predation is the most important factor determining the !ife history strategy of juvenile P. interruptus. Life history tactics promoting rapid growth apparently function dually in reducing the period of high vulnerability to predation and decreasing the time required to reach sexual maturity. The Phyllospadix habitat is an excellent lobster nursery because it provides shelter from predators and possesses abundant food resources for sustaining optimum juvenile growth rates in shallow, warm water.

Regulation of primary production in the Gulf of California through interaction of large-scale and local ocean processes [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The suppression of primary productivity observed in eastern boundary ecosystems of the Pacific during El Nino episodes does not occur throughout the Gulf of California. On the contrary, analysis of the modern siliceous phytoplankton record from annually layered sediments and compilation of available primary productivity measurements indicate that production is significantly increased in the central Gulf during El Nino years compared to anti-El Nino years. Integrated observations of biological and physical variability during the spring of 1983, under the influence of the strong El Nino, show that very high primary productivity occurred along the eastern margin of the central Gulf. This resulted from the upwelling of a nutrient rich source provided by the locally formed Gulf water mass originating in the northern Gulf. Lower productivity and phytoplankton biomass were associated with the anomalous penetration of Tropical Surface Water along the western side of the Gulf.

Statistical analyses to support guidelines for marine avian sampling: Final report. [Digital Supplements A-G attached]

Interest in development of offshore renewable energy facilities has led to a need for high-quality, statistically robust information on marine wildlife distributions. A practical approach is described to estimate the amount of sampling effort required to have sufficient statistical power to identify species specific “hotspots” and “coldspots” of marine bird abundance and occurrence in an offshore environment divided into discrete spatial units (e.g., lease blocks), where “hotspots” and “coldspots” are defined relative to a reference (e.g., regional) mean abundance and/or occurrence probability for each species of interest. For example, a location with average abundance or occurrence that is three times larger the mean (3x effect size) could be defined as a “hotspot,” and a location that is three times smaller than the mean (1/3x effect size) as a “coldspot.” The choice of the effect size used to define hot and coldspots will generally depend on a combination of ecological and regulatory considerations. A method is also developed for testing the statistical significance of possible hotspots and coldspots. Both methods are illustrated with historical seabird survey data from the USGS Avian Compendium Database.

Severe droughts reduce estuarine primary productivity with cascading effects on higher trophic levels

Using a 10-yr time-series data set, we analyzed the effects of two severe droughts on water-quality and ecosystem processes in a temperate, eutrophic estuary (Neuse River Estuary, North Carolina). During the droughts, dissolved inorganic nitrogen concentrations were on average 46–68% lower than the long-term mean due to reduced riverine input. Phytoplankton productivity and biomass were slightly below average for most of the estuary during a spring–autumn drought in 2002, but were dramatically lower than average throughout the estuary during an autumn–winter drought in 2007–2008. Droughts affected upper trophic levels through alteration of both habitat condition (i.e., bottom-water dissolved oxygen levels) and food availability. Bottomwater dissolved oxygen levels were near or slightly above average during the 2002 drought and during summer 2007. Concomitant with these modest improvements in bottom-water oxygen condition, fish kills were greatly reduced relative to the long-term average. Low-oxygen bottom-water conditions were more pronounced during summer 2008 in the latter stages of the 2007–2008 drought, and mesozooplankton abundances were eight-fold lower in summer 2008 than during nondrought years. Below-average mesozooplankton abundances persisted for well over 1 yr beyond cessation of the drought. Significant fish kills were observed in summer 2008 and 2009, perhaps due to the synergistic effects of hypoxia and reduced food availability. These results indicate that droughts can exert both ephemeral and prolonged multiyear influence on estuarine ecosystem processes and provide a glimpse into the future, when many regions of the world are predicted to face increased drought frequency and severity due to climate change.

Meteorological signals in primary productivity at two mountain lakes

Fluctuations in primary productivity at two subalpine lakes reveal both meteorological and biological influences. At Castle Lake, California, large-scale climate events such as the El Niño/Southern Oscillation affect total annual production and, combined with human fishing activity, modify the seasonal pattern of productivity. At Lake Tahoe, California-Nevada, local spring weather conditions modulate annual production and its seasonality by determining the depth of mixing and resulting internal nutrient load. Climatic conditions also contribute to deviations from the long-term trend in productivity by increasing the incidence of forest fires and through anomalous external nutrient loads during precipitation extremes. A 3-year cycle in productivity of as yet unknown origin has also been detected at Lake Tahoe.

Primary productivity in polluted environments of Bombay

The coastal areas of Bombay are generally turbid and the euphotic zone in these waters hardly exceeds 6 m. Primary productivity is largely confined to surface layers. Nearshore polluted stations have low values of dissolved oxygen, salinity and pH. Nutrients, on the other hand, are high. Primary productivity in these areas was 16.86 mg C m super(-3) d super(-1) in October. Column production for all the 4 stations ranged from 10.32 to 2511.30 mg C m super(-2) d super(-1). A direct correlation was found between nutrients and productivity values.

Study on primary production and its importance in an integrated fisheries research programme

The importance of the ocean as a source of cheap protein food is too well-known to be emphasised. In recent years there has been a tremendous increase in the fishing activity in all maritime nations and during the last few years the total world production has markedly grown. This study explains the importance of a planned exploitation according to scientific principles to preserve the availability and natural fluctuations in the abundance of stocks of marine fish and other commercially important organisms.