摘要:

A method is described for obtaining the best least-squares estimates of the parameters L∞,k, andt0when von Bertalanffy curves of the typeare fitted to observed data. This method imposes no restrictions on the number or size of the samples or on the time intervals between them. It also provides estimates of the limits of error of the parameters. The amount of computation is fairly large, but a method of systematizing it is described which makes manual computation practicable for moderate-sized sets of data. The method has been used to develop a computer program which seems to have advantages over some existing methods.A numerical example is worked out in full to illustrate application of the method.

ISSN:0706-652X    

DOI:10.1139/f66-016

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The speed at which sockeye and coho salmon swim while on spawning migration through a river was determined by direct timing of individual fish over measured river sections and by measurement of opposing water velocities. Migration was accomplished by two locomotory patterns: dart and steady swimming. For steady swimming there was a critical opposing water velocity from 1.1 to 1.7 ft/sec (mean 1.4 ft/sec). Against currents slower than the critical range steady swimming to a maximum speed of approximately 3.4 ft/sec (1.7 body lengths (L)/sec) was sustained through the observation areas, but against currents faster than the critical range salmon broke into position-holding behaviour at intervals. The calculated inter-decile range of swimming speeds (excluding slowest 10% and fastest 10%) against water velocities below the critical range was 1.75–3.18 ft/sec (0.9–1.7 L/sec) for sockeye salmon and 1.70–3.14 ft/sec (0.9–1.7 L/sec) for coho salmon. These swimming speeds were below maximum sustained values which have been determined experimentally.

ISSN:0706-652X    

DOI:10.1139/f66-017

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Zooplankton surface samples were taken with a number 12 silk bolting cloth net towed by a Clark-Bumpus quantitative plankton sampler in Narragansett Bay for 12 months. The samples were collected twice weekly, except during December, January, and February, at night at one position in the West Passage of Narragansett Bay. Ten calanoid, three cyclopoid, and one harpacticoid species of free-swimming copepod nauplii were collected from July 1957 through June 1958. The structure and arrangement of elements of the caudal armatures of these copepod nauplii showed certain differences which were utilized to develop a key.

ISSN:0706-652X    

DOI:10.1139/f66-018

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

A radioactive tracer procedure for determination of the various lecithin hydrolysing enzymes, at a low level of activity, is described. The procedure involves the use of phospholipids labeled with C14in the choline moiety as substrate and the measurement of radioactivity released in the various products of hydrolysis. The pathway of lecithin catabolism in trout muscle is via glycerylphosphorylcholine. Of the other possible routes of breakdown of lecithin, there was no indication for the activity of phospholipase C or D. Greater enzymic activity was present in the lateral line muscle than in the white muscle. The enzyme which is responsible for hydrolysis of lecithin to glycerylphosphorylcholine showed optimum activity in the vicinity ofpH 7 did not require Ca++for activity and was partially inhibited by Hg++. A lysolecithinase, showing similar properties, but having a comparatively greater activity, was also present in trout muscle.

ISSN:0706-652X    

DOI:10.1139/f66-019

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Instability of the population ofCoregonus clupeaformis(Mitchill) in southern Georgian Bay from 1948 to 1964 was evidently partly due to intensive fishing.The population was discrete at least from 1956 to 1964 as determined by extensive tagging. From 1948 to 1964, estimated effective fishing effort varied 10-fold and annual yields almost 20-fold, with two cycles of abundance and scarcity. Strength of 1951–59 year-classes, defined as population size at age III, varied 40-fold. In spite of the marked instability, the population was in recent years more stable than any other whitefish population in Georgian Bay or Lake Huron.Almost all the commercial catch was made with gill nets ofmesh. In 1957, fishing depended largely on age VII–IX fish; by 1964, on those of age V and VI. Apparent growth rate increased during this period: in 1957 age XII fish weighed 3.4 lb; in 1964 age VI weighed 3.7 lb. From 1959 to 1964, reproduction depended largely on males age IV+ and older and longer than 17 inches, and on females age V+ and older and longer than 18 inches.Natural mortality coefficients (exponential model) averaged 0.41 for fish of the 1948–58 year-classes beyond age III. Gillnetting was largely restricted to 2 months in late spring and two in fall. In each fishing season these gill nets took about 40% of the survivors of a year-class after it became fully vulnerable, at ages V, VI, and VII during the early 1960s.Combining growth and natural mortality rates in a biomass curve indicated that individual year-classes would provide highest yields when fished intensively at age IV, or slightly earlier than they were fished in the early 1960s. Yet the only hypothesis that might explain the continued existence of a fishable population was that relatively large parts of the habitat were either legally closed or unsuitable for fishing. Evidently the fishing was intense and increasing the effort would mean risk of a population collapse.

ISSN:0706-652X    

DOI:10.1139/f66-020

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Long Point Bay, on the north shore of Lake Erie, is 28.2 square miles (7278 hectares) in area, with a maximum depth of approximately 10 ft (3.05 m). Big Creek, the major tributary, drains a watershed of 317 square miles (81,818 hectares), and discharges 4700 million cubic feet (127,000 million liters) of water into the Bay annually. Summer water temperatures in the Creek and the Bay were positively correlated with air temperatures in 1962. The water in the Bay was subject to considerable seiche action. Levels of nutrients and suspended materials were characteristically higher in the Creek than in the Bay. Gross reductions in levels of turbidity, total dissolved solids, nitrates, and phosphates occurred in the lower section of Big Creek and the adjacent area of the Bay. For example, phosphate levels of bottom samples were inversely correlated with those of water samples in lower Big Creek and its estuary. The path of Big Creek discharge through the Bay to Lake Erie was defined by an analysis of total dissolved solids and soil phosphate data.

ISSN:0706-652X    

DOI:10.1139/f66-021

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Underyearling chum fry from hatchery stock were held in fresh water and salt water at two different temperatures and under two different photoperiods and acclimated to these conditions for 40 days before testing started. Aggregations were greater in salt water than in fresh water (p <.01). Fish acclimated to cold water schooled more strongly than those acclimated to warm water but this effect was not considered statistically significant. There were no differences in intensity of aggregation due to photoperiod (p >.05). The significance of these findings is discussed in relation to life history of the fry.

ISSN:0706-652X    

DOI:10.1139/f66-022

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f66-023

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f66-024

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f66-025

出版商:NRC Research Press    

年代:1966

数据来源: NRC