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Table 1
Productivity attributes and scoring thresholds used in the example PSA of the eastern Pacific Ocean purse-seine fishery (Duffy et al., 2019). Attribute definitions taken from Table 1 in Patrick et al. (2010) and refined when appropriate.
| Productivity attribute | Definition | Ranking | ||
|---|---|---|---|---|
| Low (1) | Moderate (2) | High (3) | ||
| Intrinsic rate of population growth (r) | The intrinsic rate of population growth or maximum population growth that would occur in the absence of fishing at the lowest population size. | ≤0.1 | 0.1–1.3 | >1.3 |
| Maximum age (A max years) | Maximum age is the maximum observed or predicted age, and is a direct indication of the natural mortality rate (M), where low levels of M are negatively correlated with high maximum ages. | ≥20 | 11−20 | ≤11 |
| Maximum size (L max cm) | Maximum size is correlated with productivity, with large fish tending to have lower levels of productivity, although this relationship tends to degrade at higher taxonomic levels. | >350 | 200−350 | ≤200 |
| von Bertalanffy growth rate coefficient (K) | The von Bertalanffy growth coefficient describes the rate at which a species reaches its asymptotic length, if it lived indefinitely. Here, where long-lived, low productivity stocks tend to have low values of K. | <0.095 | 0.095−0.21 | >0.21 |
| Instantaneous natural mortality rate (M) | Natural mortality rate directly reflects population productivity; stocks with high rates of natural mortality will require high levels of production in order to maintain population levels. | <0.25 | 0.25−0.48 | >0.48 |
| Fecundity (measured) | Fecundity (i.e., the number of eggs produced by a female for a given spawning event or period) is measured here at the age of first maturity. | <10 | 10−200,000 | >200,000 |
| Breeding strategy | The breeding strategy of a stock provides an indication of the level of mortality that may be expected for the offspring in the first stages of life. Estimated offspring mortality using Winemiller's (1989) index of parental investment as described in Patrick et al. (2010). | ≥4 | 1–3 | 0 |
| Age at maturity (A
mat years) (50% if available, otherwise age at first maturity) |
Age at maturity tends to be positively related with maximum age (t max); long-lived, lower productivity species will have higher ages at maturity than short-lived stocks. | ≥7.0 | 2.7−7.0 | <2.7 |
| Mean trophic level (TL) | The position of a stock within the larger fish community can be used to infer stock productivity; lower-trophic-level stocks generally are more productive than higher-trophic-level stocks. | >5.1 | 4.5−5.1 | <4.5 |
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