摘要:

Morphological and distributional observations are reported for 14 northeast Pacific sabellids, largely using collections from British Columbia and Washington waters, and for one species from New Zealand. For nine of these, additions to the descriptions are provided based on type material.EudistyliaBush is revised using a new combination of diagnostic characters.Eudistylia catharinaeis newly described;E.tenellaBush is regarded as a synonym ofE.vancouveri(Kinberg). Diagnostic characters at the generic level, particularly those ofSabellaLinnæus, are discussed.DemonaxKinberg, considered to be a subgenus ofSabella, is emended.Distylia volutacornis pacificaBerkeley and Berkeley is elevated to specific rank and referred toDemonax.Jasmineira pacificaAnnenkova,Oriopsis gracilisHartman, and an unnamed species ofSabellastarteSavigny are new additions to the polychaete fauna of British Columbia and Washington.Key words: British Columbia,Demonax,Eudistylia, northeast Pacific, Polychaeta,Sabella, Sabellidae, Washington

ISSN:0706-652X    

DOI:10.1139/f79-125

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The study area was a shallow, extremely eutrophic, somewhat brackish water bay on the south coast of Finland. Muddy odor in bream (Abramis brama) was significantly correlated with the amount of the blue-green algaOscillatoria agardhiioccurring in the phytoplankton. Cultures dominated by this alga contained the muddy odor compound geosmin. The high concentrations ofO.agardhiiin the study area were caused by several interacting factors, of which the high nutrient concentration and the temperature of the water seemed to be especially important. Odoriferous actinomycetes isolated from the water produced the muddy odor compounds geosmin and 2-methylisoborneol, but there seemed to be a lag time of several weeks between maximal concentrations of actinomycetes and development of off-flavors in the fish.Key words: geosmin, 2-methylisoborneol,Oscillatoria agardhii, actinomycetes, flavor, fish, eutrophication

ISSN:0706-652X    

DOI:10.1139/f79-126

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The inshore fishery of Lake Victoria has symptoms of severe overfishing. Curvilinear multiple regression analysis was used to examine the large variation in fishing effort, gear composition, and catches around the lake and suggest fishing practices that would give highest yields. The overfishing problem is due to the kind of gear in use and not to excessive fishing per se. Heavy fishing is often associated with the use of small mesh gillnets and seines to catch small fish such asHaplochromis, a practice that does not seem to justify the damage done to catches of the larger species by the same gear. The best strategy for maximizing the total tonnage yield is to fish optimally for the herbivorous genusTilapia. This means using only the larger gillnets appropriate forTilapia, as well as hooks, both at a very high fishing effort. The hooks capture large predators such asBagrus,Clarias, andProtopterus, an abundant resource in themselves, and simultaneously appear to increaseTilapiayields indirectly by reducing losses ofTilapiato predators.Key words: Lake Victoria, ecosystem, succession, multispecies fishery, multigear fishery, fish yield, Africa, lake, lungfish, Tilapia, Haplochromis, catfish

ISSN:0706-652X    

DOI:10.1139/f79-127

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The complexing capacities of three algal exudates and the conditional stability constants of their copper complexes have been determined by an ion exchange method. Their ability to ameliorate copper toxicity towards the primary production ofChlorella vulgarisis related to the conditional stability constants, which regulate the ionic copper concentration.Anabaena cylindrica,Navicula pelliculosa, andScenedesmus quadricaudaexcreted 6.73, 2.86, and 0.66 μmol/L of complexing ligands, respectively, with conditional stability constants of 107.7, 108.1, and 108.6, respectively, for their corresponding copper complexes. When these constants were applied in calculations, a free copper ion concentration of 10−10.3 mol/L was found in each exudate.Key words: algal exudates, free copper ion concentration, complexing capacity, copper ion toxicity, primary productivity

ISSN:0706-652X    

DOI:10.1139/f79-128

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Water samples from nine Canadian lakes were centrifuged and the pellets were analyzed by transmission electron microscopy. The pellets included small organisms, organic colloids, and clay particles. In almost all the samples, colloids were the major component revealed following thin-section analysis. When viewed at high magnification, much of each pellet consisted of morphologically discrete particles, some of which were readily categorized. Electron-opaque fibrils of colloidal size were frequently encountered (1) at different depths, (2) as a coating on the surface of algae and bacteria, (3) overlaying the sediments, (4) as an apparent adhesive between a variety of particles, and (5) as a component of froth at the water–air interface. They were common at all times and in lakes of various trophic levels and sizes.Key words: water, colloids, fibrils, lakes, electron microscopy

ISSN:0706-652X    

DOI:10.1139/f79-129

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Phytoplankton and bacteria were sampled in eight Canadian lakes and prepared immediately for thin-section analyses by transmission electron microscopy. Fibrillar colloids of probable biological origin were present at the cell surface–lake water interface of many species. Fibrillar colloids that form distinctive surface coatings on algae and bacteria are described in detail. The most common structural unit of these coatings is a ribbon-like fibril. Several types of fibril associations are documented and circumstantial evidence is presented for some possible roles of fibrillar colloids in promoting complex microbial associations and in promoting physical associations between cells and other suspended particles. The biogenesis of fibrils is also discussed.Key words: colloid, algae, bacteria, lakes, fibrils, electron microscopy

ISSN:0706-652X    

DOI:10.1139/f79-130

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Conditions are given that imply there exist policies that "minimize risk" of undesirable events for stochastic harvesting models. It is shown that for many problems, either such a policy will not exist, or else it is an "extreme" policy that is equally undesirable. Techniques are given to systematically trade-off decreases in the long-run expected return with decreases in the long-run risk. Several numerical examples are given for models of salmon runs, when both population-based risks and harvest-based risks are considered.Key words: Markov decision processes, risk, salmon management, Pareto optimal policies, trade-off curves, linear programing

ISSN:0706-652X    

DOI:10.1139/f79-131

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Based on personal observations and questionnaires to Norwegian fish farmers, the behavior of three species and several different stocks of salmonid fish reared in ocean pens is described. Swimming activity and the constancy of swimming orientation (clockwise or counter clockwise) vary among species. With few exceptions, the orientation of Atlantic salmon (Salmo salar) at any one farm does not change with tide, season, or age offish. Stock origin and/or the early rearing history may impose this directionality. The swimming of Atlantic salmon in pens resembles schooling behavior. Possible departures from this stereotyped behavior are considered. The behavior of pen-reared salmonids and its implications in selective breeding, migratory mechanisms, and fish health are discussed.Key words: salmon, behavior, pen rearing, mariculture, swimming, orientation,Salmo salar,S.gairdneri,Oncorhynchus gorbuscha

ISSN:0706-652X    

DOI:10.1139/f79-132

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Fecundity varies from year to year in blue mussels (Mytilus edulis) from Petpeswick Inlet, N.S., and from Bellevue, Nfld. This observation is consistent with recent theory that suggests that reproductive effort (that proportion of the energy budget allocated to reproduction) should be variable in animals such as marine bivalves that are unable to "predict" the quality of the environment for their juveniles. Estimates of fecundity in the sea urchin (Strongylocentrotus droebachiensis) and the snow crab (Chionoecetes opilio) are also presented. Reproductive effort increases with advancing age in the three species of invertebrates studied, although in the mussel the transition from growth to reproduction is more gradual than it is in the sea urchin or the female snow crab, which exhibit early growth and delayed reproduction. The degree to which the growth and reproductive phases are separated in each species may be determined in part by the predictability of the food supply. The allocation of resources primarily to growth rather than to reproduction in young (small) individuals may be seen as a response to selective pressure resulting from higher mortality and from competition.Key words: growth, production, reproductive strategy, energy partitioning, marine invertebrates, gametes

ISSN:0706-652X    

DOI:10.1139/f79-133

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Nutrient and essential amino acid analyses of the stomach contents of wild adult American lobsters (Homarus americanus) collected from offshore and inshore populations indicated lobsters consumed varying nutrient levels according to their stage of molt. For example, soft-shell lobsters ate a higher level of mineral constituent. The location of the animal had no effect on the level of nutrient intake. The essential amino acid composition of the protein in the stomach remained the same throughout the molt cycle, but indicated a change in protein source with the location of the animal. The relationship between crude protein and gross energy was constant suggesting its importance in the nutrition of the lobster. Based on this study, we recommend a basal level of nutrient constituents for ration formulation.Key words: American lobster, natural intake, dietary formulation

ISSN:0706-652X    

DOI:10.1139/f79-134

出版商:NRC Research Press    

年代:1979

数据来源: NRC