Estimates the absolute and relative yield and biomass per recruit and the first order derivative.
a list consisting of following parameters (not all are required):
vector with ascending fishing mortalities,
The Thompson and Bell model incorporates an iteration step simulating the
stock by means
stock_sim function. In case changes in gear
here measured in terms of Lc or tc, the length or age at first capture,
should be explored, a list with selectivity information about the gear has
to be provided and
the prediction models make use of the selectivity
Sparre and Venema (1998) recommend to treat the last length class always as plus group.
This model is very sensitive to zero observations in the ultimate length
classes. If unrealistic results are returned,
it is recommended to cut length classes with zero observations, group
them in a plus group or to change the interval between
Equations which are used in this function assume isometric growth, an
assumption often not met. Further, the assumption that there is no relationship
between the parental stock size and progeny
over a wide range of fishing mortalities or exploitation values,
respectively, is also said to be untrue. By default, the functions assume
knife-edge recruitment and selection of gears (Sparre and Venema, 1998).
A list with the input parameters and dependent on the model type following list objects:
type = 'ypr'
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Jones, R.E. 1957. A much simplified version of the fish yield equation. Doc. No. P. 21. Paper presented at the Lisbon joint meeting of International Commission Northwest Atlantic-Fisheries, International Council for the Exploration of the Sea, and Food and Agriculture Organization of the United Nations. 8 p. [Mimeo].
Millar, R.B., and Holst, R., 1997. Estimation of gillnet and hook selectivity using log-linear models. ICES Journal of Marine Science: Journal du Conseil, 54(3):471-477
Pauly, D., 1980. A selection of simple methods for the assessment of tropical fish stocks. FAO Fisheries Circulars (FAO). no. 729.
Pauly, D., 1984. Fish population dynamics in tropical waters: a manual for use with programmable calculators. ICLARM Stud. Rev. 8, 325 p.
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Sparre, P., and Venema, S.C., 1998. Introduction to tropical fish stock assessment. Part 1. Manual. FAO Fisheries Technical Paper, (306.1, Rev. 2). 407 p.
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