Make a function to calculate M vs growth for cohort

[kellijohnson-NOAA]

We used to say

% It should be noted that
% the natural mortality rate is larger than the current and future growth rate for
% the large 2010 year class.

But @andrew-edwards noted that we should have a way to calculate this.

[andrew-edwards]

Interesting .... is that to do with mortality/growth ratio for the proposed work? That's aimed at larval fish - but I hadn't thought about applying it to cohorts - nice idea.
I think there might be potential for doing something. Wouldn't happen this week, but discussing with the other collaborators would be worthwhile. Thanks.

[aaronmberger-nwfsc]

I basically have relied on the generalities of this relationship by referring to our "Calculations showing changes in biomass at each age due to natural mortality and fishing for recent strong cohorts..." table. I like the idea of having these automatically calculated because it is highly dependent on time varying selectivity and will change by cohort and year. And then we can directly look at cohort/years instead of making generalities based on the large cohorts in the aforementioned table only.

[andrew-edwards]

What we could have (and I was actually looking for the other day) is a table of median-female-spawning-biomass-at-age (like the current biomass-at-age table). Would basically kind of show some of what's in the cohort table but for every cohort. I can have a go, as was planning to create a related new table in #950 .

[kellijohnson-NOAA]

Moved to the 2024 milestone because generalizations are good enough for right now!

[kellijohnson-NOAA]

Allan noted that the following text was ambiguous

hake-assessment/doc/executive-summary/executive-summary.rnw

Lines 885 to 886 in d69b2d5

	As the large 2010, 2014, and 2016 cohorts continue to age, their biomass is expected to decrease
	as losses from mortality outweigh increases from growth. The

and suggested

"total biomass of the cohort even without fishing mortality". 

making a note here for when we address how we calculate this next year.

[aaronmberger-nwfsc]

I've made the just above Allan suggested edits to language the used the 'losses from mortality outweigh growth' statements in the assessment document.

[kellijohnson-NOAA]

Moving the rest of the task to 2025.