The relationship between predator avoidance deficits induced by a simple handling stress and the level of plasma corticosteroids was determined for juvenile coho salmon Oncorhynchus kisutch. Groups of fish were held out of water for 1 min, then allowed to recover from this stress for 1, 90, or 240 min....
Abnormalities including contortion of the body and reduction of the jaws and pectoral
fins occurred among 2-25% of the yolk-sac Pacific herring larvae Clupea harengus pallasi collected in 1985 from Kulleet Bay, a spawning area on Vancouver Island, British Columbia. An additional 4-68% of the post-yolk-sac larvae had underdeveloped lower...
Market issues are often critical to the regional and national benefits that can be generated from fisheries management. In actual policy analysis, however, market considerations are often treated as exogenous to the fisheries policy problem. Examples illustrate the relationships between product characteristics, market demand, and regulatory management. A multiple-objective socioeconomic...
Length of survival of the monogenetic trematode Gyrodactylus stellatus in serum and mucus collected from English soles Pleuronectes vetulus at different stages of a laboratory epizootic suggests that both the mucus and serum may be involved in resistance to the parasite. In general, trematode survival was shorter in the serum...
The fisheries literature embodies critical assumptions about fisherman attitudes and motivations. Common assumptions are that populations of fisherman are homogeneous in motivation and decision making and that they behave in a myopic fashion, ignoring the effects of their fishing activities on the fishery resource. The results of a survey of...
In ocean fisheries for Pacific salmon Oncorhynchus spp., there can be several forms
of gear-related mortality. Much research effort has been directed at estimating mortality rates for salmon that are hooked and then released. Also potentially important but not easily measured is mortality of fish that escape from the hook...
Intense infections of the gill pathogen Dermocystidium salmonis were associated with mortality of prespawning chinook salmon Oncorhynchus tshawytscha in several Oregon rivers in 1988. The occurrence of the pathogen in returning adult chinook salmon was monitored in several coastal Oregon stocks from 1989 to 1993. Although the prevalence of the...
Two species of salmonids were tested for their susceptibility to infection by a rickettsia isolated in cell culture from diseased coho salmon Oncorhynchus kisutch in Chile. Mortality approached 100% in coho and Atlantic salmon Salmo salar injected with 10-fold dilutions of cell culture medium containing the rickettsia. Typical disease signs...
Cell lines were established from spleen and heart tissues of a juvenile white sturgeon Acipenser transmontanus and designated WSS-2 and WSH-1, respectively. Isoenzyme analyses of both lines confirmed their host of origin. Both lines were hypotetraploid and possessed micro- and macrochromosomes. The modal chromosome number for the WSS-2 line was...
Monoclonal antibodies (MAbs) directed against the snakehead rhabdovirus (SHRV) were produced. These MAbs were characterized by immunofluorescence and neutralization tests, and by their ability to immunoprecipitate viral proteins. Of 15 MAbs developed, 9 were isotyped as IgG1 and 6 were IgG2a. Eight of the MAbs recognized the viral glycoprotein in...
Protein profiles and serological characteristics of 3 rhabdoviruses from snakehead fish Ophicephalus striatus were determined and compared to 5 known fish rhabdoviruses and 1 mammalian rhabdovirus. The snakehead rhabdovirus (SHRV) exhibited a bacilliform morphology and a Lyssavirus-type protein profile. The ulcerative disease rhabdovirus isolates (UDRV-BP and UDRV-19) were indistinguishable and...
An indirect fluorescent antibody test (IFAT) was developed for detection of the rickettsia that was causing epizootics among salmonids cultured in seawater net-pens in southern Chile. Antiserum against the rickettsial agent was produced in New Zealand white rabbits with a preparation grown in antibiotic-free chinook salmon embryo (CHSE-214) cell cultures...
Research was undertaken to examine the influence of light intensity on the shoaling behavior, activity and anti-predator behavior of juvenile walleye pollock Theragra chalcogramma. Under a 12 h light/12 h dark photoperiod, juveniles displayed a diurnal shoaling and activity pattern, characterized by fish swimming in cohesive groups during the day,...
The effects of reduced food availability on the behavior of juvenile walleye pollock Theragra chalcogramma were examined in laboratory experiments designed to test for potential energy-conserving responses. Groups of juvenile fish were held on 1 of 6 ration treatments ranging from ad libitum to near starvation, and then vertical distribution...
Walleye pollock and sablefish, as 0+ yr juveniles, are pelagic particulate feeding planktivores. We conducted a series of laboratory experiments to determine how illumination influences prey consumption in these species, utilizing live Artemia sp. as prey. Both juvenile walleye pollock and sablefish were characterized by a sigmoidal relationship between the...
Prior studies have demonstrated that juvenile walleye pollock Theragra chalcogramma forage socially in schools for spatially and temporally clumped food, but forage more independently for spatially and temporally dispersed food. One advantage of social foraging is that fish in schools may be able to locate more food clumps than fish...
We quantified both in situ predation on Pacific herring (Clupea haregus pallasi ) larvae by soft-bodied zooplankton, and microzooplankton prey of herring larvae in Kulleet Bay, Vancouver Island, British Columbia. Samples were collected at 0 to 5 m depth daily at peak larval hatching from 14 to 21 April 1985....
This study examined, under controlled laboratory conditions, behavioral responses of larval walleye pollock (4 to 8 mm) to various physical factors that may potentially play a role in vertical movements and distribution. Diel periodicity in vertical distribution was evident and appeared to be under exogenous control. During the day, with...
Population dynamics of coral reef fishes and spiny lobster appear to be determined by variable recruitment interacting with post-settlement processes, particularly predation. The risk of predation may be modified by the scaling between prey and shelter size, which enhances the protective capacity of a reef. We experimentally tested these predictions...
While growth and survival of marine fish larvae in the sea may be dependent on prey type, size and concentration, nutritional quality of prey may also play an important role. This study investigates the relationships of lipid content of prey with growth, gas bladder size, sinking rate, behavior and survival...
The impact of mesoscale eddies on the spatial distribution of zooplankton biomass was analysed using data from the Arabian Sea and the Black Sea. The highest values of spatial variance of zooplankton biomass in the upper 100 to 150 m were found in regions with maximum available potential energy of...
Global increases in ultraviolet-B radiation (UVBR) have the potential to alter marine primary production and to affect carbon cycles and marine trophic dynamics. Estimates of UVBR induced photoinhibition have varied greatly, indicating that a common dose-response by marine phytoplankton may not occur from place to place. An action spectrum describing...
Submersible belt-transect surveys along a rocky bottom were combined with acoustic surveys of the water column to estimate depth distribution and density of fishes at Stonewall Bank, Oregon in the northeastern Pacific Ocean from September through October 1991. The objectives of the study were to determine the proportion of fish...
Heceta Bank is a large reef on the edge of the central Oregon continental shelf that supports a wide variety of commercial fisheries. Using the research submersible Delta, we studied fish abundances on Heceta Bank and the relationship between species composition of fish assemblages and bottom types. Cluster analysis indicated...