摘要:

A method is described for catching the planktonic larval stages of the lobster (Homarus americanusMilne Edwards). Estimates are made of the abundance and distribution of each of the four stages in the surface waters of part of the Northumberland Strait (southern Gulf of St. Lawrence) for the years 1949–61, with a more critical analysis for the year 1961. Both abundance and survival of the larvae vary from year to year, although they do not appear to be related with measured hydrographical conditions. It is suggested that the distribution of stage I larvae reflects the location of the parent stock and that surface drift carries the developing larvae to possible areas of settlement.There is no conclusive relationship between the larvae and the subsequent stock, although a possible relationship between the abundance of stage I larvae and parent stock density is described and briefly discussed.

ISSN:0706-652X    

DOI:10.1139/f64-060

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Lernaeopoda centroscyllii, a lernaeopodid copepod parasitic onCentroscyllium fabricii, and briefly described by Hansen on the basis of one damaged female specimen in 1923, has not been recorded since that date. This paper gives a detailed account of both the male and the female of the species, recently taken in Newfoundland waters.

ISSN:0706-652X    

DOI:10.1139/f64-061

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Three genetically distinct subpopulations of the Pacific sardine have been differentiated by the frequency of occurrence of a C-positive blood factor. Two of these subpopulations, a northern and a southern one, live off the coast of California and the outer coast of Baja California, Mexico. The third group inhabits the Gulf of California. The C-positive factor occurred in 13.6% of the northern subpopulation, 6.0% of the southern, and 16.8% of the Gulf subpopulation.

ISSN:0706-652X    

DOI:10.1139/f64-062

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

The concentrations of fat, water-solubles, protein, and water in cod muscle are subject to seasonal variations. During the period of spawning, there is a decrease in fat (−20%) and protein (−5%) paralleled by an increase of water-solubles (+10%) and water (+5%). The return of these major components to their average annual values occurs at various rates. The seasonal emaciation of cod is closely linked to the physiological processes taking place in the animal's body during the reproductive activities.

ISSN:0706-652X    

DOI:10.1139/f64-063

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

A technique is described for insertion of a cannula in the dorsal aorta of salmon for long-term blood sampling or vascular injection while the fish is confined, but free-swimming. Previous methods for single injections into the dorsal aorta are improved by a modified cannulation technique. The practicality of the technique was tested by introducing Evans Blue (T-1824) into the dorsal aorta of immature pink salmon (Oncorhynchus gorbuscha) in sea water and mature sockeye salmon (O.nerka) in fresh water to make preliminary estimates of blood volumes. It was shown that the technique can also be applied to angiography of salmon.

ISSN:0706-652X    

DOI:10.1139/f64-064

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Uniformity of temperature in the region of the initial freezing point (30.5°F or −0.8 °C) was observed in blocks of dressed fish and skins-on shore cod fillets thawed in a 38 Mc/s commercially installed electronic thawer. In general, highest surface temperatures were about 40°F (4.5 °C) only.Drip losses on thawing were 2.4% for plant-prepared skins-on fillets of trap cod dipped in a 9% solution of sodium tripolyphosphate prior to freezing and about 1% for fall-caught shore fish similarly handled. This was much less than the estimated gain (approximately 7%) resulting from the application of the dip. Two lots of untreated skins-on fillets of fall-caught shore fish developed drip losses of 2.2 and 2.5%, respectively.

ISSN:0706-652X    

DOI:10.1139/f64-065

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Several methods for the estimation of population size and natural mortality are used and evaluated, for the Nogies Creek maskinonge, with consideration being given to the sources of error and correcting factors discussed by Muir (1963a). The Schumacher tagging method and a method using only catch and average exploitation are found to be equally useful.The same catch and exploitation method is used to estimate natural mortality and the estimates agree with those from the Beverton and Holt type method. Both methods suffer from large year-to-year errors but the 9-year average appears to be a useful statistic. Natural mortality increases with age and is about 15% per year for age IV and older and about 24% per year for age V and older.There is only a 2-fold variation in the estimated age IV size of year-classes. The smallest of 9 year-classes was 302 and the largest was 604. No effect of fishing on subsequent year-class production could be demonstrated during the period of study. Heavy fishing did, however, remove large numbers of older fish with a resultant increase in catchability of the younger fish.

ISSN:0706-652X    

DOI:10.1139/f64-066

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Analysis of the fatty acid composition of a marine diatom,Skeletonema costatum, shows that the longer-chain highly unsaturated fatty acids characteristic of fish lipids can be produced by some phytoplankton as well as through intermediary zooplankton. Comparison of cultures of various degrees of maturity indicates that the fatty acid composition of mature cultures in laboratory experiments is not necessarily typical of pelagic diatoms. The origin of atypical C16-polyunsaturated fatty acids is discussed.

ISSN:0706-652X    

DOI:10.1139/f64-067

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Three distinguishable size groups of oocytes are contained in the ovary of the viviparous poeciliid,Lebistes reticulates— small, middle-sized, and large. At parturition some of the middle-sized oocytes develop into large oocytes and subsequently, upon fertilization, into embryos. The number of middle-sized oocytes is then replenished from a large store of small oocytes. The effect of changes in the amount of available food on these oocytes and hence on the number of offspring was explored by an experiment involving 27 femaleLebistes. Rations varying from near starvation to normal were supplied over the course of three consecutive parturition periods. At the end of the third period each fish had received a different combination of the three rations. Variations in first-period rations affected the numbers of both first- and second-period offspring. Reduced numbers of offspring and reduced large and middle-sized oocyte counts were associated with reduced rations. No significant changes in the size of young or the length of the gestation period were observed.

ISSN:0706-652X    

DOI:10.1139/f64-068

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Anin-vivostudy was made of potential precursors of trimethylamine oxide (TMAO) in marine teleosts (lemon sole,Parophrys vetulus, and starry flounder,Platichthys stellatus). C14-labelled compounds were administered intraperitoneally and the incorporation of tracer into TMAO, isolated from the whole body, was determined. Trimethylamine (TMA)-C14was found to be a much better precursor than the other compounds tested. A limited labelling of TMAO was observed after administration of γ-butyrobetaine-methyl-C14, betaine-methyl-C14and methionine-methyl-C14. There was little or no incorporation of C14into TMAO after administration of methylamine-C14, carnitine-methyl-C14, gIycine-2-C14, sodium formate-C14, sodium acetate-1-C14, sodium acetate-2-C14and NaHCO3-C14. The conversion of choline-methyl-C14to TMAO was higher after intraperitoneal than after intramuscular injection and only trace amounts of radioactivity were found after intravenous injection. The results provide support for formation of TMAO in fish by oxidation of TMA but they give no clear indication for metabolic pathways leading to this oxidative step.Betaine was isolated from fish after administration of choline-methyl-C14, methionine-methyl-C14and glycine-2-C14. Evidence of extensive conversion of choline to betaine was obtained. Betaine also was found to be labelled after administration of methionine-methyl-C14, but only a limited degree of labelling was observed after administration of glycine-2-C14. The results indicate that betaine is formed by oxidation of choline in fish.A modification of the Dragendorff reagent for use as a spray for detecting trimethylammonium compounds on paper chromatograms is described.

ISSN:0706-652X    

DOI:10.1139/f64-069

出版商:NRC Research Press    

年代:1964

数据来源: NRC