Aquat. Living Resour.
Volume 35, 2022
|Number of page(s)||17|
|Published online||07 October 2022|
Table 1. Observed von Bertalanffy growth parameters used to analyze CYPR14.
Table 2. Observed weight–length scales (A) and exponents (B) used to analyze CYPR14 for L. stappersii in Lake Tanganyika (lengths were in mm and weight in g) and L. niloticus in Lake Victoria (lengths were in cm and weight in g).
Figure 1. Scatter plots and marginal boxplot distributions of the random draws of (a) and (b) the von Bertalanffy growth parameters and (c) and (d) weight–length scales and exponents for L. stappersii in Lake Tanganyika (left panels) and L. niloticus in Lake Victoria (right panels).
Figure 2. Frequency distributions of (a) and (b) natural mortality (M), (c) and (d) asymptotic weight (W8), (e) and (f) mass of the average recruit (wr), and (g) and (h) the rate of metabolic loss of body mass (μ) for L. stappersii in Lake Tanganyika (left panels) and L. niloticus in Lake Victoria (right panels). The dashed blue line represents the mean of the distribution.
Figure 3. Variations, against age, of mean (black solid line), median (blue dash-dotted line), and the 95% uncertainty envelops (gray area) of biomass for an unfished cohort of L. stappersii in Lake Tanganyika and L. niloticus in Lake Victoria. The age-specific biomass Ba was given by Ba = lawa, where wa (kg) is mean weight at age a and la is the survivorship to age a: la = 1 if a = 0 year and la = la-1exp(-M) = exp(-aM) if a > 0; M is natural mortality. Mean biomass, median biomass, the 95% lower biomass limit, and the 95% upper biomass limit of L. stappersii peaked at ages 3, 3, 2, and 4 years. Such summaries statistics for L. niloticus peaked at ages 7, 7, 6, and 7 years.
Figure 4. Isopleths of the mean composite spawning-stock per recruit (CSSR) as a function of fishing mortality (F) and the age of knife-edge recruitment or the age of knife-edge selection r for L. stappersii in Lake Tanganyika (left panels) and L. niloticus in Lake Victoria (right panels). The CSSR of the top plots was calculated considering that the survivorship to each age r is 1 (Eq. (1), Tab. 2) and the CSSR of the bottom plots involved the declining survivorship to each age r (Eq. (5), Tab. 2).(Access here)
© J. Munyandorero, Published by EDP Sciences 2022
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