Showing papers on "Pelagic zone published in 1974"

The Ocean's Food Web, A Changing Paradigm

Abstract: Few of us may ever live on the sea or under it, but all of us are making increasing use of it either as a source of food and other materials, or as a dump. As our demands upon the ocean in- crease, so does our need to understand the ocean as an ecosystem. Basic to the understanding of any ecosystem is knowledge of its food web, through which energy and materials flow. Flux of both energy and essential elements shapes or limits ecosystems, but only energy and organic compounds are con- sidered here. The related problems of limiting supplies of essential elements (N, P, Si, Fe) will be considered else- where (Pomeroy'). Although the ocean's food web has been studied for more than a century, several recent discoveries lead us to believe that the classical textbook de- scription of a chain from diatoms through copepods and krill to fishes and whales may in fact be only a small part of the flow of energy. Recent studies of microorganisms, dissolved organic mat- ter, and nonliving organic particles in the sea suggest the presence of other pathways through which a major part of the available energy may be flowing. Marine scientists have been approaching this view of the food web cautiously for decades, and caution is to be expected whenever an established paradigm is questioned (Kuhn 1962). Now there are many lines of evidence which suggest that a new paradigm of the ocean's food web is indeed emerging. THE ROLES OF MICROORGANISMS ocean, with 90% of the total area and the lowest mean rate of photosynthesis, accounts for 81.5% of primary produc- tion. Coastal waters over the continental shelves, with 9.9% of the total area and twice the rate of photosynthesis of the open ocean, account for 18% of primary production. The major upwellings, with 0.1% of the total area and a rate of photosynthesis nearly 10 times that of the open ocean, account for 0.5% of primary production. The real accuracy of these estimates is not as good as the three digit numbers suggest. The usual methods of estimating the photo- synthetic rate of phytoplankton do not measure all organic matter produced, and there is rarely enough replication to give us confidence limits for the values. The most obvious plants in the sea are the seaweeds, but they probably are not the most significant primary pro- ducers. Ryther (1963) estimates that seaweeds account for 10% of the pri- mary production of the ocean. Recent data on photosynthetic rates of kelp and other large seaweeds (Mann 1973) make that estimate seem high, although it is still difficult to make a good estimate on a planetary scale. Certainly, seaweeds and sea grasses are of major importance in the coastal zone. On a planetary scale phytoplankton are the major producers. Phytoplankton have been divided into two size groups, net plankton and nannoplankton. The separation is arbitrary, based on the aperture of what was once the finest bolting cloth for making plankton nets. Net plankton (>60 pm) have received considerable attention and form the basis of the established paradigm of the food web, but nannoplankton (<60 pm) have proven more difficult to study and until recently they have been neglected. Like net plankton, they are so sparsely distributed in the water that it is neces- sary to concentrate them in some fashion to see them at all. Because many of them cannot be preserved well, they must be studied at sea while alive. Only recently has high magnification, oil- immersion microscopy at sea permitted the study of living nannoplankton aboard ships. Efforts to understand the relative importance of net and nannoplankton have been made by several investigators, using the 14C technique (Steeman- Nielsen 1952), by counting separately the radioactivity retained on discs of bolting cloth and on fine membrane filters. This was a crude separation. Some organisms larger than the aperture of the bolting cloth would be forced through it in fragments, and if a suf- ficiently thick layer of plankton ac- cumulated on the bolting cloth, nanno- plankton would be retained by it. In spite of these shortcomings, at least a dozen studies produced consistent re- sults showing that the large diatoms and other net plankton, although highly visible and beautiful, account for a small fraction of total primary production. In a majority of cases nannoplankton ac- count for more than 90% of total photosynthesis (Table 1). This is true not only in the central gyres of the ocean, but in upwellings, coastal waters, and estuaries. No one seems to have made the separation in polar regions. However, Digby (1953) found that in Scoresby Sound, Greenland, nanno- plankton chlorophyll was always equal

The Spread of Sibling Larvae of Sedentary Marine Invertebrates

Abstract: 1. It is unlikely that individual selection simply for increasing distance between juveniles or between juveniles and parents would produce the patterns of reproduction and large-scale dispersal exhibited by many benthic invertebrates with pelagic larvae. However, these patterns are compatible with the hypothesis that pelagic larval phases of several weeks are the result of individual selection for spreading sibling larvae. 2. Selection for spread of siblings as a fixed feature of the life cycle depends on survival and reproduction in the benthic phase of life and in early and late larval stages varying independently from time to time and place to place. Data on benthic populations is apparently insufficient to determine whether or not such variation occurs. However, information on horizontal diffusion rates gained from dye diffusion experiments indicates the geographic scale of independent variation required by the hypothesis. 3. Rate of diffusion in the sea increases with time (or size of diffusing patc...

On predation of pelagic larvae and early juveniles of marine bottom invertebrates by adult benthic invertebrates and their passing alive through their predators

Abstract: The dynamic quantitative balance between prey and predator invertebrate species inhabiting the same shallow-shelf (sublittoral level bottom) benthic communities was first discussed by Thorson (1953). Thorson considered the exact timing of larval settlement of prey and predator species possessing pelagic development and temporal supression of the adult predators' feeding activities during reproduction at the time of the preys' settlement to constitute the major factors which facilitate survival of the prey species in such communities. However, information obtained demonstrates that Thorson's “mechanism of balance between predator and prey species of benthic communities” is not always effective in securing survival from predation not only of the prey's spat but even sometimes of the predator's spat also. Because of this, the “mechanism” can not be rated as universally effective in all situations. Analysis of the data so far published demonstrates that, in marine benthic communities, especially in shallow-shelf waters, it is not uncommon for gametes, larvae, or early juveniles of different prey species to pass alive through suspension (filter)-feeding and deposit-feeding adult invertebrates preying on them. Sometimes development can even continue after excretion by predators. The hypothesis of Voskresensky (1948) and Goycher (1949) of the importance of this phenomenon for the maintenance and recruitment of the mussel Mytilus edulis and other filter-feeding lamellibranchs of nearshore waters preying on their own and other lamellibranch pelagic larvae must be rejected on the basis of accumulated data on their feeding and general biology and on the adverse influence of the mucous of their faecal pellets and pseudofaeces on the larvae excreted by them alive. The data considered here demonstrate that, although the passing alive of larvae and spat of benthic invertebrates through benthic predators is not uncommon in shallow-shelf bottom-communities, it plays no important role in the processes of maintenance and recruitment of the species and communities involved nor of the marine benthos as a whole. The actual ecological significance of predation on pelagic larvae and bottom spat of benthic invertebrate prey species by all three main trophic groups of marine benthos (suspension or filter-feeders, deposit-feeders, carnivores) and its importance to predator-prey dynamics in marine benthic communities remains open to debate until more reliable quantitative data become available.

The settlement, distribution and movements of O‐group plaice Pleuronectes platessa (L.) in Filey Bay, Yorkshire

Abstract: The pelagic larval stages and the demersal O-group stage of plaice were sampled in the immediate vicinity of Filey Bay, Yorkshire (54°12′N, 00°16′W), using a modified Gulf V high-speed plankton sampler and beam trawls. The distribution and movements of these fish were studied from the time of first settlement in May through the period of metamorphosis and the O-group stage. It was found that the larvae settled in water deeper than 5 m and moved into shallow water following metamorphosis. This established a typical distribution of larger fish in shallower water than the smaller fish. When the fish grew over 40 mm they moved out again into deeper water which leads to a reversal of the lengthdepth distribution. Further movements during the winter months and of the I-group fish were studied by tagging. It was found that emigration from the nursery ground did not occur until the I-group stage.

Laboratory Studies of Predation by Euphausiid Shrimps on Fish Larvae

Abstract: Despite a large literature on the vulnerability of marine fish larvae to changes in their physical and biotic environment, there is surprisingly little quantitative data available on organisms that eat fish larvae. There is ample evidence that huge mortalities of yolk-sac fish larvae occur (Ahlstrom, 1965); this is not due to lack of food, a factor implicated in the mortality of older larvae (Blaxter, 1969). Predation on yolk-sac larvae may be the most important cause of mortality during the early period in the life history of pelagic fish. There are a number of observations of zooplankters feeding on fish larvae (Garstang, 1900; Lebour, 1925; Wickstead, 1965; Petipa, 1965; Fraser, 1969); copepods, chaetognaths, ctenophores, and a variety of coelenterates have been seen to capture and ingest marine fish larvae. Recently Lillelund and Lasker (1971) quantified the predatorprey relationship between several species of marine copepods and larvae of the northern anchovy, Engvaulis mordax, and described the behavioural responses involved in this interaction. They found, for example, that a variety of marine copepods (but particularly surface-dwelling pontellids) can capture and ingest or fatally injure young anchovy larvae under laboratory conditions.

Distribution of pelagic blue-green algae in the North Pacific Ocean

Abstract: The distribution of pelagic blue-green algae, especially ofTrichodesmium thiebautii, was investigated on the basis of the collection of theHakuhō Maru Cruise KH-69-4 along 155°W (50°N-15°S) in the North Pacific Ocean from September to November 1969.

Fish Bulletin 162. Pelagic Fish Surveys In The California Current

Abstract: The California Department of Fish and Game started routinely acoustically surveying the smaller schooling pelagic fish resources in the California Current System in 1966. This report covers the first 6.5 years of these surveys (1966–1973). The purpose of these surveys was to determine the abundance, distribution, availability, and other pertinent biological information of the commercially important northern anchovy, jack mackerel, Pacific sardine, and Pacific mackerel. Latent resource species including Pacific saury, Pacific hake, squid, and pelagic red crab also were surveyed. The principal technique consisted of running acoustic transects with a horizontal ranging sonar and vertical echo sounder during daylight hours and fishing a midwater trawl at night. Results show the northern anchovy grossly dominates all other species in terms of biomass and abundance with the southern California-northern Baja California region containing most of the total population. Although it was not possible to determine absolute population size, results indicate the estimates of 2 to 6 million tons made from egg and larvae surveys are reasonable. Behavior and availability studies indicate that although the anchovy population is large, its vulnerability to harvest by the present commercial fishery varies considerably from year to year as well as seasonally. Most of the common schooling behaviors are unfavorable for effective harvest by roundhaul net. Only a small portion of the population is harvestable during any particular time period. Acoustic surveys were much less effective for estimating abundance of Pacific sardines, Pacific mackerel, and jack mackerel. The distribution of jack mackerel was patchy with nearly all significant concentrations located at a limited number of rocky banks and island coasts. Pacific sardine and Pacific mackerel population levels in California were apparently too low to assess. There were indications of larger populations of both species in Baja California. of the latent resource species under survey, pelagic red crabs and market squid appear to be the most favorable for future exploitation. However, the crabs are located almost entirely within Mexican territorial waters and the vulnerability of squid for large scale harvest is uncertain.

Production of pelagic Sargassum and a blue‐green epiphyte in the western Sargasso Sea1

Abstract: North of 30°N Sargassum production averaged about twice that to the south, possibly related to the degree of winter mixing. Production rates were relatively high in continental shelf areas or near land masses but showed no major seasonal variations nor was there an obvious relationship with concentrations of NO2, NO3, NH3, and PO4. Under normal daylight conditions in October Sargassum photosynthesizes at a maximum rate. Average carbon turnover time is no more than 40 days and Sargassum and its epiphytes contribute no more than 0.5% of the total primary production in the western Sargasso Sea. Carbon turnover rate of the epiphyte Dichothrix exceeded that of its host Sargassum by an average of fourfold. Dichothrix production on the shelf averaged as much as 15% of the pelagic macroalgal production in October. Dichothrix is most abundant in the continental shelf waters and lowest in the Sargasso Sea; this distribution may be related to the available iron in the seawater.

Food of the Larval Anchoveta Engraulis ringens J.

Abstract: The Peruvian fisheries have developed very quickly during the last ten years, resulting in Peru becoming the foremost fishing country in the world The fishery is largely based on the anchoveta Engraulis vingens J, a pelagic fish sufficiently abundant to support catches of up to 10 × 106, tons, although 12,000,000 TM were taken in 1970

Pelagic studies of seabirds in the central and eastern Pacific Ocean

Abstract: King, Warren B., Editor. Pelagic Studies of Seabirds in the Central and Eastern Pacific Ocean. Smithsonian Contributions to Zoology, number 158, 277 pages, 170 figures, 1974.—Seven papers by various authors on the pelagic distribution of several seabirds in the central and eastern Pacific Ocean based largely on the researches of the Pacific Ocean Biological Survey Program, 1963-1968. "Introduction," by Patrick J. Gould, introduces these and future papers in this series. He discusses the methods and procedures used by the POBSP in gathering and recording data on observations of seabirds, outlines the areas under surveillance, and provides a general account of the oceanography and marine biology of the areas under discussion as a background to understanding the movements of seabirds in relation to their environment. "Sooty Tern (Sterna fuscata)," by Patrick J. Gould, presents the POBSP'S records of this most abundant tropical and subtropical Pacific species. Its distribution at sea depends on erratic food availability, location of breeding islands, breeding schedule, and postbreeding dispersal patterns. "Wedge-tailed Shearwater (Puffinus pacificus)," by Warren B. King, gives data on the distribution of the northern, predominantly white-breasted and the southern, darkbreasted morphs of this species. Subtropical populations migrate extensively, for example between the Hawaiian Islands and the Pacific coast of Middle America; tropical populations are apparently nonmigratory. "Black-footed Albatross (Diomedea nigripes)," by Gerald A. Sanger, discusses the distribution and frequency of sightings on a seasonal basis of this ship-following seabird, both in general terms throughout its range and in detail in certain areas, for example, the CalCOFI study covering an eight year period oft California and Baja California. Its winter range overlaps largely with, but lies slightly to the south of, its summer range. "Laysan Albatross (Diomedea immutabilis)," by Gerald A. Sanger, analyzes observations of this species and relates its seasonal distribution and abundance to its oceanographic environment. This species is more abundant in the western and central Pacific, whereas the Black-footed Albatross is more abundant in the central and eastern Pacific. "The Storm Petrels (Hydrobatidae)," by Richard S. Crossin, summarizes the POBSP'S data on eighteen species or subspecies of storm petrels based on sightings and collected specimens. Pelagic distribution is related to breeding cycles, location of breeding sites, and marine environment. "Red-tailed Tropicbird (Phaethon rubricauda)," by Patrick J. Gould, Warren B. King, and Gerald A. Sanger, discusses seasonal distribution and abundance of this species relative to its breeding cycle. This species disperses widely from its breeding islands, for example, from the Hawaiian Islands to the Pacific coast of Middle America. "Recoveries of Banded Laysan Albatrosses (Diomedea immutabilis) and Black-footed Albatrosses (D. nigripes) in the Pacific Ocean," by Chandler S. Robbins and Dale W. Rice, summarizes the seasonal distribution of pelagic recoveries of 324 banded Laysan Albatrosses and 399 banded Black-footed Albatrosses. Different age groups of each species concentrate in somewhat different areas, and, although range overlap between species is almost complete, each has its own distinctive seasonal distribution pattern. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 4901. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus) . Library of Congress Cataloging in Publication Data Main entry under title: Pelagic studies of seabirds in the central and eastern Pacific Ocean. (Smithsonian contributions to zoology, no. 158) "Seven papers by various authors . . . based largely on the researches of the Pacific Ocean Biological Survey Program, 1963-1968." Bibliography: p. 1. Sea birds—Pacific Ocean. 2. Pacific Ocean Biological Survey Program. I. King, Warren B., ed. II. Series: Smithsonian Institution. Smithsonian contributions to zoology, no. 158. QL1.S54 no. 158 [QL694] 591'.08s [598.4'09164] 73-10383 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Price $3.70

Group orientation in Neomysis mirabilis (Mysidacea: Crustacea)

Abstract: The orientational behaviour of the neritic mysid Neomysis mirabilis in a swarm is considered under natural and experimental conditions. In nature, the swarms exhibit elements of inner integration, such as homogeneous age structure, collective behaviour, and relative constancy of inter-individual spacing. The mysids are guided by combined optomotor and vibrotactile cues, determining their disposition in aquaria of different shapes. Maximum accuracy of spatial arrangement is observed in round vessels. It is suggested that the stress encountered in an aquarium produces responses comparable to those elicited by the presence of a predator. The rigid spatial arrangement at the supra-individual level is interpreted as evolutionally-optimized prey strategy. These elements in the geometrical distribution of individuals in mysid swarms are inherent in other pelagic crustaceans also, and are not controlled by random taxes stimulated by hydrological factors.

Biology of the small pelagic fishes in the New Volta Lake in Ghana. Part III: Sex and reproduction

Abstract: Reproductive patterns of five species, from three families, of small pelagic fishes in the new Volta Lake in Ghana showed several similar features. These included sex size defferences, males maturing and reaching final sizes smaller than females; heterogenous sex ratios in four species, being most markedly unequal usually at peak breeding times; demersal eggs; and extended fractional spawning patterns. The clupeids Pellonula and Cynothrissa and the cyprinid Barilius all breed in the dry season, whereas the schilbeids Physailia and Siluranodon are wet-season spawners. Only Pellonula and Physailia have extended their breeding season in the new lake to cover most of the year; the other species have not, although Siluranodon spawns into the early dry season. In the lake environment Pellonula's pelagic larva is no longer endangered by seasonal floods, whereas Physailia can use the lake's continuous “high waters” for extended breeding. Relaxation of breeding patterns and protracted fractional spawning has allowed best exploitation of the new regime.

Vertical and seasonal distribution of pelagic cephalopods in the Mediterranean Sea Preliminary Report

Abstract: Although benthic and neritic cephalopoda of the Mediterranean Sea have been studied since Aristotle first observed Octopus behavior, the pelagic forms have received very little attention. The Mediterranean Biological Studies Program of the Smithsonian Institution, an outgrowth of the Ocean Acre Program in the Sargasso Sea (see Gibbs and Roper, 1970; Gibbs et. al., 1971), provided the opportunity to study in detail the midwater macrofauna with particular emphasis on diel vertical distribution of species and their seasonal and geographical variation in occurrence and abundance. The precision and detail required for collecting specimens for such a study was achieved through use of a net-closing device, the discrete-depth cod-end sampler, rigged to a 3 m Isaacs-Kidd Midwater Trawl (IKMT) (Aron et. al., 1964). This instrument permits collecting of three replicate samples at any desired depth during a single lowering of the trawl. The closing devices are actuated from shipboard through use of a multiconductor towing warp; monotoring of depth of net and ambient temperature permits precise placement and control of the fishing depth of the trawl during each tow. Five localities were selected as collecting stations (Figure 1) and were sampled during the summer of 1970 and the winter of 1972. The sampling regime consisted of IKMT discrete-depth tows both day and night at 50, 100, 150, 200, 300, 400, 500, 600, 800 and 1000 meters and neuston tows at the surface. Sampling at all depths for all stations was not possible to complete because of lack of time. Station I was not sampled in winter. Station data are presented elsewhere (Gibbs, 1972). During the two cruises a total of 591 cephalopods, representing 21 species, was captured: 362 specimens representing 15 species in summer; 229 specimens representing 17 species in winter. A total of 760.2 hours was spent in trawling; trawling time was about equally divided between the two cruises (summer: 368.1 hrs; winter: 392.1 hrs). All species captured were members of the North Atlantic fauna, so no endemic component of the Mediterranean fauna is represented. A preliminary report on the cephalopods

Feeding, Starvation and Weight Changes of Early Fish Larvae

Abstract: The present study concerns weight changes, first feeding, and early starvation in the larvae of Tilagia sparmanii A Smith, a tropical freshwater fish with attached eggs, and in Paralichthys olivaceus (Temmik et Schlegel), a common marine flatfish in Japan, with discrete pelagic eggs Such studies are of importance when investigating survival and growth of fish larvae

Some observations on the relative abundance of biological sound scatters in the North-eastern Atlantic Ocean, with particular reference to apparent fish shoals

Abstract: In various months of the years between 1960 and 1972, the R.R.S. “Discovery II” and R.R.S. “Discovery” carried out a number of echo-surveys in the North-eastern Atlantic Ocean between Latitudes 12° and 62°N, and from the European and African coasts to a longitude of approximately 29°W. The prime objective was to acquire data on sea-floor topography. In addition, numerous echo-traces of biological scattering present in midwater between depths of approximately 35 and 460 m were obtained. The traces were of variable quality, but were considered suitable for a preliminary evaluation of the scattering mainly as a basis for further investigation. The scattering recorded in daytime was broadly divisible into three types: (1) Diffuse layers, which were probably due to dispersed single fish. These were not analysed further. (2) Very small discrete echoes, mostly derived from single fish and very small shoals. These were mapped to show geographical regions of greater abundance. (3) Larger discrete echoes, most of which were almost certainly given by fish shoals. These were analysed in detail and information obtained on depth distribution, shoal density, geographical distribution and relative abundance. Small and moderate-sized shoals were found to be very numerous in spring and summer in oceanic water to the West and North-west of the British Isles. Large numbers of shoals of various sizes were also observed at various time of the year in the Bay of Biscay and near certain parts of the European and African Continental Shelf, near certain seamounts, and near islands such as the Azores, Madeira, and the Cape Verde Islands. In general, shoals appeared to be relatively sparse in the more southerly temperate and subtropical regions of the open ocean. The depth distribution of shoals in open water varied greatly but, on average, the maximum daytime depth of those in the more southerly area of the survey was slightly greater than that of those in the more northerly area. Shoal size also varied, shoals to the north of Latitude 50°N were on average slightly smaller than those detected in southerly regins. Possible identification of the fish is discussed.

Food Habits of Landlocked Salmon and Brook Trout in a Maine Lake after Introduction of Landlocked Alewives

Abstract: Stomach analysis of landlocked Atlantic salmon and brook trout from Echo Lake, Maine, indicated that salmon relied more on open water prey (landlocked alewives, rainbow smelt and terrestrial insects) than did brook trout, which fed more on bottom and shoreline prey (sticklebacks, killifish and aquatic invertebrates). Most fish were eaten by salmon and trout in summer and few were eaten in winter. Young-of-the-year alewives constituted an important portion of the salmon diet, especially in late summer, but were not significant forage for trout. The isopod Asellus racovitzai racovitzai was important forage for trout in winter and spring. A review of studies concerning food habits of salmon and trout indicates utilization of pelagic forage fish is related to lake area.

On the vertical distribution of pelagic tunicates in relation to the water masses in the western part of the Bay of Bengal

Abstract: A study on the vertical distribution of pelagic tunicates in relation to the water masses in the western part of the Bay of Bengal is made. Their depth distribution has clearly pointed out that while some pelagic tunicates are primarily associated with water conditions similar to those of the Northern Dilute Water and Transition Water, the others were associated with the water conditions similar to those of the Southern Bay of Bengal Water and Upwell Water. The present study supports the observations made earlier on the horizontal and depth distribution of pelagic tunicates in the western part of the Bay of Bengal.

Distribution of pelagic Polychaetes in the North-West Australian Sea during winter

Abstract: Out of 32 species of pelagic polychaetes recorded in the Indian Ocean only 17 are found in the north-west Australian Sea during December 1963 and January 1964. A distinct pattern in the distribution of a few tropical species is observed in the area north of 170s. The species like Sagitella kowalevskii and Phalacrophorus uniformis commonly met with in the 1st yr are totally not encountered in the samples from the same area in the 2nd yr. The northern tropical zone is not only rich in species but also in abundance.

Our pelagic fishery resources Present and potential harvest

Abstract: The two primary divisions of the oceans are (1) the benthic and (2) the pelagic, the former referring to the ocean floor which supports the demersal resources and the latter, the entire column of water , accomodating the pelagic resources. The pelagic region is a part of the marine biocycle and geographically, it is divisible into Atlantic and Indo-Pacific. Ecologically, the pelagic realm can b e bifurcated as neritic (inshore) and oceanic (opens e a) provinces d epending on the depth to which light penetrates and to the extent and depth of the continental slope