hom: Horse mackerel (Trachurus trachurus) off the portuguese coast
In ALKr: Generate Age-Length Keys for fish populations

A dataset containing data collected in two bottom-trawl surveys carried out in the Portuguese coast in 1992 and 1993, and data generated and sampled from it.

A list of 9 elements

Proportions of each age class in the catch (pj) were calculated using classic Age-Length Keys built from the surveys' data. Mean length at age (lmed) was given values close to the ones observed in the real data, and its standard deviation (stdv) was calculated as suggested by Schnute and Fournier (1980).

The two catch matrices N1992 and N1993 were generated from this data, and the F1992 and F1993 were calculated from them.

The otoliths list contains a total of 1000 length-stratified random samples, extracted from the N1992 matrix. Each of these samples simulate process of the sampling of a small subset of fish from the total catch to analyze its otoliths for age determination. The age data then obtained can then be used either alone or in combination with length data to calculate Age-Length Keys for the population.

The data is presented as a list containing the following items:

lmed. Mean length at age.
stdv. Standard deviation of length at age.
pj_1992. Proportions of each age-class in the catch (1992 survey).
pj_1993. Proportions of each age-class in the catch (1993 survey).
N1992. Number of individuals per length and age class (1992 survey).
N1993. Number of individuals per length and age class (1993 survey).
F1992. Number of individuals per length (1992 survey).
F1993. Number of individuals per length (1993 survey).
otoliths. A list of 1000 length-stratified samples taken from N1992.

Schnute, J., Fournier, D. (1980). A New Approach to Length-Frequency Analysis: Growth Structure. Canadian Journal of Fisheries and Aquatic Sciences, 37(9), 1337-1351. DOI: 10.1139/f80-172

ALKr documentation built on May 30, 2017, 7:42 a.m.