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Angermeier, P. L.; Smogor, R. A. |
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Titel |
Estimating number of species and relative abundances in stream-fish communities: Effects of sampling effort and discontinuous spatial distributions |
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Jahr |
1995 |
Publikation |
Can. J. Fish. Aquat. Sci. J. Can. Sci. Halieut. Aquat |
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52 |
Ausgabe |
5 |
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936-949 |
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Schlüsselwörter |
Fisch, Fließgewässer, Habitat, Verbreitung |
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Zusammenfassung |
The authors sampled fishes and measured microhabitat in series of contiguous habitat units (riffles, runs, pools) in three Virginia streams. Monte Carlo simulations were used to construct hypothetical series of habitat units, then examined how number of species, similarity in relative abundances, and number of microhabitats accumulated with increasing number of habitat units (i.e., sampling effort). The curves indicated that 90% of the species present were usually found by sampling 5 to 14 habitat units (stream length of 22-67 stream widths). Estimates of species relative abundances required less sampling effort for a given accuracy than estimates of number of species. Rates of species accumulation (with effort) varied among streams and reflected discontinuity in species distributions among habitat units. Most discontinuity seemed to be due to low population density rather than to habitat selectivity. Results from an Illinois stream corroborated our findings from Virginia, and suggested that greater sampling effort is needed to characterize fish community structure in more homogeneous stream reaches. |
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Natl. Biol. Serv., Virginia Coop. Fish Wildl. Res. Unit, Virginia Polytech. Inst., Blacksburg, VA 24061-0321, USA |
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nein |
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Rufnummer |
620 |
Signatur |
2414 |
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Hoenig, J. M.; Morgan, M. J.; Brown, C. A. |
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Analysing differences between two age determination methods by tests of symmetry |
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Zeitschrift, Artikel |
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Jahr |
1995 |
Publikation |
Can. J. Fish. Aquat. Sci. J. Can. Sci. Halieut. Aquat |
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52 |
Ausgabe |
2 |
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364-368 |
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Schlüsselwörter |
Altersbestimmung, Fischerei, Statistik, Methode |
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Zusammenfassung |
A common problem in fisheries science is the comparison of two methods for obtaining ages of individual animals. The authors suggest that if the overall level of agreement is low between two ageing methods used on the same sample of fish, then one can use a test of symmetry to look for evidence of systematic disagreement. A chi super(2) test is used to determine if the number of fish assigned age i from method 1 and age j from method 2 differs significantly from the number of fish assigned age j from method 1 and age i from method 2. Such a test can also be used to determine the range of nominal ages over which two methods appear to give comparable results. |
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Dep. Fish. and Oceans, P.O. Box 5667, St. John's, NF A1C 5X1, Canada |
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Rufnummer |
532 |
Signatur |
2331 |
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Myers, R. A.; Cadigan, N. G. |
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Titel |
Statistical analysis of catch-at-age data with correlated errors |
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Zeitschrift, Artikel |
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Jahr |
1995 |
Publikation |
Can. J. Fish. Aquat. Sci. J. Can. Sci. Halieut. Aquat |
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52 |
Ausgabe |
6 |
Seiten |
1265-1273 |
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Fisch, Fischerei, Statistik, Wachstum, Mortalität, VPA, Population, Mathematik, Modell |
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Zusammenfassung |
The statistical model used is extended to estimate abundance from commercial catch-at-age data for many of the major commercial fish species in the world. The model combines commercial catch-at-age data and research survey estimates of fish abundance; extends the model to allow correlated errors among ages within a year for the survey estimates of fish abundance. Method is formulated for modeling the fishing mortality on the oldest ages of the fish caught. Estimates are obtained using maximum likelihood. The level of correlation among ages is sufficiently large to produce large biases in the standard methods for some stocks. The statistical model that includes correlated errors greatly reduces bias and increases efficiency if the correlation in the estimation error is large. |
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Dep. Fish. Oceans, Sci. Branch, Box 5667, St. John's, NF A1C 5X1, Canada |
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Rufnummer |
528 |
Signatur |
2327 |
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Autor |
Walters, C. |
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Titel |
Estimation of historical stock sizes and recruitment anomalies from relative abundance time series |
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Zeitschrift, Artikel |
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Jahr |
1995 |
Publikation |
Can. J. Fish. Aquat. Sci. J. Can. Sci. Halieut. Aquat |
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52 |
Ausgabe |
7 |
Seiten |
1523-1534 |
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stock-assessment; approximation-; anomalies-; recruitment-; abundance-; growth-; survival-; algorithms-; fishery-management; marine-fisheries |
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Often only simple relative abundance time series and basic growth and (or) survival estimates are available for assessing impacts of fishing and environmental factors. Assessment then involves fitting production models to the series, while forcing the model with observed catch or effort series. A key uncertainty in this approach is how to deal with recruitment variations due to factors other than stock size. A dynamic programming algorithm can be used to compute maximum likelihood estimates of the recruitment anomaly sequence, given prior knowledge of growth parameters, the natural survival rate, and proportion of the variation in the relative abundance index that is due to abundance measurement errors. |
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Zu bestellen |
Geprüft |
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Rufnummer |
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Signatur |
1779 |
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Autor |
Wang, Y. G.; Thomas, M. R. |
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Titel |
Accounting for individual variability in the von Bertalanffy growth model |
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Zeitschrift, Artikel |
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Jahr |
1995 |
Publikation |
Can. J. Fish. Aquat. Sci. J. Can. Sci. Halieut. Aquat |
Kurztitel der Zeitschrift |
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Band |
52 |
Ausgabe |
7 |
Seiten |
1368-1375 |
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Schlüsselwörter |
Fisch, Statistik, Methode, Vergleich, Wachstum, Bertalanffy, Faben |
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Zusammenfassung |
Estimation of von Bertalanffy growth parameters has received considerable attention in fisheries research. Since Sainsbury much of this research effort has centered on accounting for individual variability in the growth parameters. In this paper we demonstrate that, in analysis of tagging data, Sainsbury's method and its derivatives do not, in general, satisfactorily account for individual variability in growth, leading to inconsistent parameter estimates (the bias does not tend to zero as sample size increases to infinity). The bias arises because these methods do not use appropriate conditional expectations as a basis for estimation. |
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CSIRO IPP&P Biometrics Unit, CSIRO Div. Fish., Box 120, Cleveland, Queensland 4163, Australia |
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Rufnummer |
524 |
Signatur |
2323 |
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