| Einträge |
Autor  |
Mertz, G.; Myers, R. A. |
| Titel |
Estimating the predictability of recruitment |
Typ |
Zeitschrift, Artikel |
| Jahr |
1995 |
Publikation |
Fish. Bull |
Kurztitel der Zeitschrift |
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| Band |
93 |
Ausgabe |
4 |
Seiten |
657-665 |
| Schlüsselwörter |
recruitment-; mortality-; developmental-stages; fishery-biology; fishery-management; environmental-factors; stock-assessment; Pisces-; population-dynamics; models- |
| Zusammenfassung |
A simple analytical technique is developed for estimating the predictability of recruitment, that is, correlations between recruitment and stage-specific mortalities or abundances. The method requires the input of estimates of the variability of stage-specific mortalities, which may be calculated from mean stage-specific mortalities by applying a published regression. It is shown that modification of this regression to compensate for sampling error in field measurements of abundance significantly reduces the estimated standard deviation of log-recruitment, which is an important factor in the predictability calculations. It is concluded that the prospects for predicting recruitment from egg or larval surveys or from environmental variables are quite poor for fish stocks showing the typical distribution of mortality across stages. |
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1090 |
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| Autor |
Porch, C. E. |
| Titel |
Trajectory-based approaches to estimating velocity and diffusion from tagging data |
Typ |
Zeitschrift, Artikel |
| Jahr |
1995 |
Publikation |
Fish. Bull |
Kurztitel der Zeitschrift |
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| Band |
93 |
Ausgabe |
4 |
Seiten |
694-709 |
| Schlüsselwörter |
dispersion-; migrations-; tagging-; Pisces-; swimming-; models-; dispersal-; migration- |
| Zusammenfassung |
Several new models are developed to estimate the velocity and diffusion of a population from tagging data. The new estimators apply the inverse principle to the individual trajectories of recovered tags rather than to their local abundance. These models require fewer assumptions and less information than do published abundance-based methods. Techniques are presented for a variety of circumstances, and both discrete and continuous parameterizations of the velocity field are included. The sensitivity of the estimators to violations of the assumptions was examined numerically by using stochastic simulations. The results suggest that the estimators are fairly robust but may fail under certain conditions. Extensions to accommodate these situations are discussed. |
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1295 |
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