Tag-recapture Data Research Articles

The Loggerhead Turtle, Caretta-Caretta, in Queensland - Population Breeding Structure

Population models proposed as a result of independent tagging programs of nesting Caretta caretta in Queensland are in disagreement about the size of discrete breeding units. An electrophoretic survey was conducted to assess the relevance of genetic variation as revealed by electrophoresis to the investigation of Caretta caretta population breeding structure. Low level electrophoretic variability (H*L(obs) = 0.016) was found. The geographical distribution of alleles, when compared with tag-recapture data and other aspects of life history, indicated that discrete breeding populations of C. caretta in Queensland are larger than previously thought. C. caretta nesting on the mainland beaches and on the cays of the Capricornia Section of the Great Barrier Reef Marine Park form a panmictic population. The data indicate that those nesting on the Swain Reefs cays do not interbreed with the mainland-Capricornia breeding population.

Lake Whitefish (Coregonus clupeaformis) Stocks of the Ontario Waters of Lake Huron

Historical and contemporary data on lake whitefish (Coregonus clupeaformis) from the Ontario waters of Lake Huron were examined for evidence of stocks with the objective of defining population boundaries. We delineated the spatial distribution of five stocks from tag–recapture data and the general location of six additional stocks on the basis of population parameters such as growth rate, age structure, and abundance trends.Samples of fish collected (summer and fall) from 5 of the 11 potential stocks were evaluated on the basis of 11 morphometric and 7 meristic characters. We also examined osseometric features such as shape of scales and otoliths, and electrophoretic characteristics at 32 loci associated with 12 enzyme systems.The summer and fall samples for each group were generally not significantly different. For the phenotypes examined electrophoretically, each stock was in Hardy–Weinberg equilibrium; 12 of the 32 loci considered were polymorphic and 4 of the 10 possible genetic distances differed significantly from zero.The Inner Basin stock was distinctly different from all other stocks. The Blind River stock was also found to be different by osseometrics, but not by morphometrics or electrophoresis. Osseometrics separated the stocks by basin of origin. Two stocks, Outer Basin and Burnt Island, appeared to be the most similar and could be separated from each other only on the basis of growth rate and tagging data. These two stocks are adjacent to each other in the main basin of Lake Huron, along the south shore of Manitoulin Island.Whitefish stocks of Lake Huron represent groups of fish that differ phenotypically and genotypically in varying degrees, are spatially separated, and behave as cohesive units. We conclude that they should be regarded as functional units for management purposes.Key words: lake whitefish, Coregonus clupeaformis, Lake Huron, stocks, tag–recapture data, population structure, morphometrics, meristics, osseometrics, scale and otolith shape, starch gel electrophoresis, biochemical genetic variation

Growth of the saucer scallop, Amusium japonicum balloti Habe, in central eastern Queensland

Tag-recapture data were used to determine growth and movement of A. japonicum balloti. The von Bertalanffy growth model was found to be suitable for describing growth in the latter half of the size range for A. japonicum balloti, and estimated S∞ of scallops varied with year and area. A. japonicum balloti grows rapidly, being recruited to the commercial fishery at about 6 months of age in some cases. Recapture data indicated that A. japonicum balloti does not undergo long-distance displacements in its post-larval stage.

Estimating and Testing Differences between Population Levels by the Schnabel Estimation Method

In the Schnabel method of estimating number of animals, the number of recaptures has been assumed to follow a Poisson distribution. This approximation is useful in testing differences in population levels when the Schnabel method is used for estimation, since the distribution of recaptures from one population, conditional on the total number of recaptures from both populations, is approximately binomial with parameters n and p, where p is a function of the parameters of the two Poisson distributions. Tests based on this conditional binomial distribution are described. Confidence limits of the population numbers have been considered and a stop rule developed for the Schnabel experiment used at the second stage of a paired comparison. The Schnabel method (Schnabel 1938) of estimating numbers of animals from tagrecapture data is widely used in fish and game population studies. This method is popular because (1) computations are simple, (2) daily estimates are a feature of this method, enabling the field worker to see his results as the work progresses, and (3) the method is flexible and can reasonably be expected to provide useful results over a wide range of capture conditions. However, there is some hesitancy about using the Schnabel method, since the variances of these estimates are difficult to estimate. In addition, it has not been made clear whether tests of differences between estimated populations can safely be based on such estimates of variance, as is also true for confidence intervals about an estimate. Simple straightforward tests of differences in population level, as well as confidence limits for the population estimate, are possible by using the knowledge that the number recaptured has approximately a Poisson distribution (Chapman 1954). To estimate population size by the Schnabel method, let x x-= number of recaptures, (1) A(n,M,), (2) 1=1

標識率法による東京湾北部のマハゼ資源量の推定

The tagged ratio method already introduced by the Author, was applied to the tag-recapture data of Japanese common goby, Acanthogobius flavimanus in the northern part of Tokyo bay, from 1955 to 1959. The results showed that the population size of this goby in the area were about 1 ?? 2 hundred millions at the period from middle of September to beginning of October, though of course there were some yearly variation. Otherwise, the results obtained by common PETERSEN method, based on the same data, were clearly overestimates, caused by the successive diminution of tags. The average value of weekly natural mortality coefficient, obtained by the tagged ratio method and BEVERTON method together, was about 0.0519 at the prime fishing season from middle of September to beginning of November in this area. Furthermore, 0.10 ?? 0.20 for the exploitation rate, (1×10-6 for the catchability coefficient), and 0.60 ?? 0.70 for the survival rate during same period, were calculated respectively.