ypr: Yield per recruit

Description Usage Arguments Details Value References

View source: R/ypr.R


Estimates the absolute and relative yield and biomass per recruit and the first order derivative.


ypr(param, FM_change, t = NA)



a list consisting of following parameters (not all are required):

  • Linf: infinite length in cm,

  • Winf: infinite weight,

  • K: growth coefficent for investigated species per year [1/year],

  • t0: theoretical time zero, at which individuals of this species hatch,

  • M: natural mortality,

  • tr: age of recruitment,

  • tc: age of first capture;


vector with ascending fishing mortalities,


default NA


The Thompson and Bell model incorporates an iteration step simulating the stock by means of the stock_sim function. In case changes in gear characteristics - here measured in terms of Lc or tc, the length or age at first capture, respectively - should be explored, a list with selectivity information about the gear has to be provided and the prediction models make use of the selectivity select_ogive function. 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 length classes. 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:


Berkeley, S.A., and Houde, E.D., 1980. Swordfish, Xiphias gladius, dynamics in the Straits of Florida. ICES C.M., 11.

Beverton, R.J.H., and Holt, S.J., 1964. Table of yield functions for fishery management. FAO Fish. Tech. Pap. 38, 49 p.

Beverton, R.J.H., and Holt, S.J., 1966. Manual of methods for fish stock assessment. Pt. 2: Tables of yield functions. FAO Fisheries Technical Paper, (38)Rev.1:67 p.

Boerema, L.K., and J.A. Gulland, 1973. Stock assessment of the Peruvian anchovy (Engraulis ringens) and management of the fishery. Journal of the Fisheries Board of Canada, 30(12):2226-2235

Garcia, S. and N.P. van Zalinge, 1982. Shrimp fishing in Kuwait: methodology for a joint analysis of the artisanal and industrial fisheries. pp. 119-142 In: Report on the Workshop on assessment of the shrimp stocks of the west coast of the Gulf between Iran and the Arabian Peninsula. Fisheries development in the Gulf. Rome, FAO, FI:DP/RAB/80/015/1, 163 p.

Gulland, J.A., 1983. Fish stock assessment: a manual of basic methods. FAO/Wiley, New York.

Gulland, J.A. and Boerema, L., 1973. Scientific advice on catch levels. Fish. Bull. (US) 71:325-335.

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.

Pauly, D. and M. Soriano. 1986. Some practical extensions to Beverton and Holt's relative yield-per-recruit model, p. 491-495. In J.L. Maclean, L.B. Dizon and L.V. Hosillos (eds.) The First Asian Fisheries Forum. Asian Fisheries Society, Manila.

Schaefer, M.B., 1954. Some aspects of the dynamics of populations important to the management of the commercial marine fisheries. Inter-Am. Trop. Tuna Comm., Bull. 1(2):27-56.

Schaefer, M.B., 1957. A study of the dynamics of the fishery for yellowfin tuna in the eastern tropical Pacific Ocean. Inter-Am. Trop. Tuna Comm., Bull. 2:247-268.

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.

TropFishR documentation built on Oct. 4, 2021, 9:06 a.m.