diff --git a/slides/dogfish-rpr-slides.Rmd b/slides/dogfish-rpr-slides.Rmd index 654ec4b..ad6d518 100644 --- a/slides/dogfish-rpr-slides.Rmd +++ b/slides/dogfish-rpr-slides.Rmd @@ -641,14 +641,6 @@ include_graphics("../figs/length-age-comparison.png") - High variability in length-at-age relationship, but dogfish also difficult to age (Appendix C.1) ] ---- -# Natural mortality - -- Estimated from maximum observed age and meta-analytic equation (Hamel and Cope 2022): $M = 5.4/A_\textrm{max} = 0.065$ -- Maximum age of 85 years (observed in the 1980s, G. MacFarlane) -- Sex-invariant natural mortality given similar longevity between females and males -- Alternative values explored in population modeling (0.057, 0.074) - --- ## BC + US samples vs. US-assessment estimated @@ -705,6 +697,14 @@ Based on Ketchen (1972); convert length to age include_graphics("../figs/ss3/set_a_mat/fecundity.png") ``` +--- +# Natural mortality + +- Estimated from maximum observed age and meta-analytic equation (Hamel and Cope 2022): $M = 5.4/A_\textrm{max} = 0.065$ +- Maximum age of 85 years (observed in the 1980s, G. MacFarlane) +- Sex-invariant natural mortality given similar longevity between females and males +- Alternative values explored in population modeling (0.057, 0.074) + --- # Unfished replacement line @@ -729,12 +729,12 @@ class: center, middle, inverse .xsmall[ Sex segregated age-structured population model (Stock Synthesis 3) fitted to fishery & survey catch, indices, and size composition. McAllister-Ianelli algorithm to downweight the sample sizes of size composition. -Estimated selectivity, unfished recruitment, and stock-recruit productivity. - -Adjust maturity ogive for two year gestation period. On average, half of mature females give birth annually. +Estimated selectivity, unfished recruitment, and stock-recruit productivity parameter. No recruitment deviations (cohorts not observable from length data). +Adjust maturity ogive for two year gestation period. On average, half of mature females give birth annually. + In essence, a production model informed by catch and indices, while size composition informs selectivity. Age-structure incorporates lags in stock response to exploitation pattern (selectivity and fishing mortality). @@ -743,11 +743,11 @@ Age-structure incorporates lags in stock response to exploitation pattern (selec --- ## A stock-recruit curve for Dogfish-like species -Low fecundity limits stock productivity. Example to illustrate: +Low fecundity limits productivity of closed populations. Example to illustrate: -Imagine an unfished population N = 100 adults, which produce 10 pups/adult, that's 1,000 pups (B0). If pup survival to recruit life stage is 0.6, then we have 600 recruits (R0). +Unfished population N = 100 adults, each produce 10 pups = 1,000 pups (B0). If pup survival to recruit life stage is 0.6, then we have 600 recruits (R0). -A population of N = 20 (0.2 B0) produces 200 pups. If steepness were 1 in a closed population, we'd have to conjure 600 recruits from 200 pups. +A population of N = 20 (0.2 B0) produces 200 pups. If steepness were 1, we'd have to conjure 600 recruits from 200 pups (proof by contradiction). Thus, in this example, steepness should be capped at 0.33: 200 pups at 0.2B0 divided by 600 pups when unfished. @@ -793,7 +793,7 @@ From base model **A0**, explored various uncertainties in the set of models (Wor - Growth (**A2–A4**) - Natural mortality (**A9–A10**) - Discard mortality rate (**A5**, **A14**) -- Inclusion/exclusion and weighting of index from modern surveys (**A7**, **A8**, **A13**) +- Inclusion/exclusion, weighting of index from modern surveys (**A7**, **A8**, **A13**) - Stock-recruit productivity (**A11–A12**) - Cause of decline in modern indices (fishery vs. non-fishery causes) (**B1–B5**) @@ -844,7 +844,7 @@ include_graphics("../figs/ss3/set_a_mat/N_age_A1.png") .tiny[ Oscillations in age classes demonstrate of the lagged effects in the population. -Early Vitamin A fishery fished out older animals (age 30+), population recovered from younger cohorts invulnerable to the fishery. +Early Vitamin A fishery fished out older females (age 30+), population recovered from younger cohorts invulnerable to the fishery. ] ] @@ -865,9 +865,9 @@ include_graphics("../figs/ss3/set_a_mat/spawning_est.png") .pull-third-right[ .tiny[ -Estimated steady decline in population biomass +Top: Estimated steady decline in population biomass -Different trend in spawning output (due to differences in selectivity & maturity): declines after vitamin A fishery, subsequent recovery, and another decline +Bottom: Different trend in spawning output (due to differences in selectivity & maturity): declines after vitamin A fishery, subsequent recovery, and another decline ] ] @@ -926,7 +926,7 @@ include_graphics("../figs/ss3/set_a_mat/sel_age_max1.png") .tiny[ - Selectivity estimated by size, converted to age. Compare with maturity ogive (dotted black line) -- From size composition, landed catch is mostly female, discards have more even sex ratio +- From size composition, landed catch is mostly female, discards have more equal sex ratio - Immature females are caught incidentally, e.g., bottom trawl discards ] @@ -960,7 +960,7 @@ include_graphics("../figs/ss3/set_b/M_year.png") ``` .small[ -- Natural mortality roughly doubles in B-set of models +- Natural mortality roughly doubles in B-set of models (above replacement value) ] @@ -987,7 +987,7 @@ include_graphics("../figs/ss3/prof/like_zfrac.png") .tiny[ - Stock-recruit productivity parameter $z_\textrm{frac}$ hits lower bound, i.e., there are no MSY reference points -- Presented results with $z_\textrm{frac}$ = 0.4, following US assessment +- Fixed $z_\textrm{frac}$ = 0.4 for most models, following US assessment ]