摘要:

An extended exponential growth phase and a higher maximum population characterized growth of planktonic algae in a dialysis system compared with that in a batch system. Algal cells grown in a dialysis culture had higher chlorophyll content and a larger average cell size than those grown in a batch culture. In both types of culture, changes in cell-size distribution were related to the phases of the growth cycle with maximum cell-size during the stationary phase. Various interactions of the component reactions of photosynthesis leading to changes in growth pattern and cell-size distribution are discussed.

ISSN:0706-652X    

DOI:10.1139/f73-028

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Periodical tests made on 272 fillets from fresh, postrigor, trawler-caught cod have shown that there is a slight decrease in salt-extractable proteins during the spring spawning period (March, April, and May). This was accompanied by a similar slight decrease in the lipid content of the muscle.When other fillets from these same lots of cod were frozen and stored at − 3.3 C and − 12 C, those from the fish caught during the spring spawning period tended to deteriorate faster, as indicated by the rate at which the EPN values decreased during storage. When the fish were stored at − 26 C for up to 2 years, the EPN changes during storage were so retarded that seasonal differences in storage quality could not be observed.

ISSN:0706-652X    

DOI:10.1139/f73-029

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The population of bloodworms (Glycera dibranchiata) at Wiscasset, Maine, is composed of five assumed year-classes. Most spawners are probably large 3- and 4-year-old bloodworms. At Wiscasset eggs are released into the coelom at a size of 21 μ. The rate of egg growth varies with season. In June 1–10 million eggs are spawned at a diameter of 151–160 μ. A bottom temperature in excess of 13 C seems necessary for spawning to occur. Spawning occurs in the afternoon, between 2 hr before and 1 hr after high water. Males emit streams of sperm while swimming at the surface; females swim rapidly at the surface and suddenly rupture, liberating all the eggs at once. Females are slightly more abundant than males in the flats. Spawning bloodworms are preyed upon by herring gulls (Larus argentatus) and striped bass (Morone saxatilus), while spent epitokes are consumed by the mud shrimp (Crangon septemspinosus), which in turn is eaten by striped bass.

ISSN:0706-652X    

DOI:10.1139/f73-030

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Organic pollution was a major factor in limiting the abundance and diversity of Gastropoda and Pelecypoda in the Ottawa River near Ottawa–Hull. Analyses of 472 Ekman grab samples taken from May to November of 1968 showed that the average standing crops (no./m2) of mollusks were larger in areas immediately upstream than in areas immediately downstream of slaughter house and pulp and paper mill outfalls.

ISSN:0706-652X    

DOI:10.1139/f73-031

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Tracks of three types of fishing gear in bottom sediments were observed from a submersible in Chaleur Bay (Gulf of St. Lawrence). Tracks left by past otter trawling activities covered at least 3% of the bottom by area and were considered to have been made by trawl doors.Shallow tracks made by inshore and offshore scallop dredges during the course of the study could be distinguished from each other and from trawl tracks.Scallop dredging lifts fine sediments into suspension, buries gravel below the sand surface, and overturns large rocks embedded in the sediment, appreciably roughening the bottom. The inshore Alberton dredge is inefficient, dumping its contents back onto bottom at intervals during the tow.Dredging causes appreciable lethal and sublethal damage to scallops left in the track, this damage being greatest on rough bottom. Incidental mortalities to scallops with an offshore dredge of at least 13–17% per tow are of the same order of magnitude as estimates of harvesting efficiency made in earlier studies.Predatory fish and crabs were attracted to the dredge tracks within 1 hr of fishing and were observed in the tracks at densities 3–30 times those observed outside the tracks.

ISSN:0706-652X    

DOI:10.1139/f73-032

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Samples of the infaunal invertebratesNephtys incisaandYoldia limatulafrom Narragansett Bay, Rhode Island, have been analyzed for their fatty acid distribution. Based on total fatty acids,Yoldiacontains 9–16% of an acid tentatively identified as 22:2. The ratios of 18:1/18:0 and 18:1/20:1 fatty acids ofNephtysfrom a polluted station in the bay are lower than the corresponding ratios for animals from relatively clean areas.

ISSN:0706-652X    

DOI:10.1139/f73-033

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Multiple isozymes of glycerol-3-phosphate dehydrogenase (L-gIycerol-3-phosphate: NAD oxidoreductase, E. C. 1.1.1.8) have been resolved by starch gel electrophoresis of extracts of muscle tissue from lake whitefish (Coregonus clupeaformis). The isozyme electropherograms show that three kinds of subunit, A, B, and C, are synthesized in red muscle and two of these, A and B, are also found in white muscle. In red muscle the subunits evidently combine to form catalytically active dimers of the following types: AA, AB, BB, BC, and CC. In white muscle only the AA, AB, and BB dimers were observed.A genetic and molecular structure model is proposed for the glycerol-3-phosphate dehydrogenase (G-3-PDH) isozymes in white muscle of lake whitefish. On the basis of two alleles for A subunits and three alleles for B subunits, the model predicts a total of 18 distinct, electrophoretic G-3-PDH phenotypes for all possible AA, AB, and BB dimeric isozymes. The model has been confirmed by the results of a breeding experiment that tested the heritability of each of the five known alleles. A difference in the rate of heat inactivation of AA and BB isozymes was also interpreted as additional evidence for the unique genetic and molecular nature of the two kinds of subunits.Surveys of natural populations of lake whitefish revealed some marked variations in the frequencies of G-3-PDH alleles in fish from different geographical areas.The cisco (Coregonus artedii) also appears to have three "b" alleles for G-3-PDH.

ISSN:0706-652X    

DOI:10.1139/f73-034

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The value of RNA–DNA ratio as a measure of long-term growth of fish populations under semi-natural conditions and when subjected to environmental manipulations was determined. Populations of carp and smallmouth bass of known age distribution were established in artificial ponds maintained at two fertility levels. After 15 months, population growth rates (as percent increase in weight) and RNA–DNA ratios of muscle tissue from selected fish were measured. Each species exhibited a range of population growth rates. The relation between population growth rate and individual fish RNA–DNA ratio for each species was significant. When reproduction occurred, the relation was not significant unless young-of-the-year fish were excluded from population growth rate calculations. Age of fish was also found to have an important effect on RNA–DNA ratio, with the ratio being higher in younger fish.RNA–DNA ratio can be a reliable indicator of long-term population growth in fish when population age structure is known and recruitment is controlled. The method has potential for use in detecting response to environmental changes before growth rate changes become severe.

ISSN:0706-652X    

DOI:10.1139/f73-035

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Rates of gastric acid and pepsin secretion into the gastric juice were examined in terms of enzymatic activity (measured spectrophotometrically as tyrosine released from hemoglobin substrate) and total gastric enzyme secretion (calculated from secretion of14C-labelled protein) at various intervals up to 9 hr following introduction into the stomach of one or two glass beads representing approximately 0.62 and 1.26% of the bluegill (Lepomis macrochirus) body weight, respectively. Observations of enzymatic activity and concentration suggested that gastric secretory reserves would have been depleted 6 hr after consuming a meal equalling 1.26% of the fish body weight. Decreased acidity of gastric juice 5 hr after ingesting two glass beads supported this interpretation. The importance of these data to efficiency and growth studies is discussed.

ISSN:0706-652X    

DOI:10.1139/f73-036

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A new nonparasitic species of Petromyzontidae,Lampetra pacifica, from streams of Oregon and California is described and illustrated. This species is distinguishable fromLampetra richardsoni, its nearest relative, by fewer myomeres, body proportions, pronounced pigmentation inside the buccal cavity, patterns of pigmentation of the head and tail, and geographical distribution. The description is based on an examination of 233 specimens (43 transformed individuals and 190 ammocoetes).

ISSN:0706-652X    

DOI:10.1139/f73-037

出版商:NRC Research Press    

年代:1973

数据来源: NRC