I also think the 1,219,000 pounds estimate is on the low side as well. We reestimate previous years, every year, the assumption is that with another years added information we have a more accurate model. I expect that 1,219,000 will be increased between 1 – 4%. Not much but yes I think it’s on the low side. It results from the poor gill net results this year.
Using the reestimation method 2019 spawning stock biomass was actually updated to 1.5 million pounds. That was probably the 2013 year classes peak abundance and health year. Recruitment in 2019 and 2020 was poor if I remember correctly. So as 2013 yc has been harvested or died naturally new yc have not done well to replace those fish, not yet anyways. I’m optimistic.
The biomass is estimated using many more methods than just one years gill net results. Juvenile assessments, plumpness, catchability, probably others, I’m not a modeler. Those numbers over the last 15 years are all included. That way one years gill net assessment dosn’t have too much model influence. Because as you said gill net assessments vary.
We run our own models as well, but that MN DNR model seems to be the most accurate and we use that one for quota setting.
As far as giving back, or going over. It’s worth considering, but it’s not super straightforward. When quota is “given back” it dosn’t necessarily survive to the next year. Fish die naturally, and since we deal in terms of biomass, they loose, or gain weight. I do expect we will move towards some sort of going over/giving back plan. I’d like to see it happen the very next year, as ecosystems change year to year.
This type of plan could cause problems for our intertribal allotments, but thats our problem and we can deal with it.
Hooking mortality. I don’t know as much as I’d like to, I don’t calculate those. It’s pretty basic now that only temperature and released fish are the only parameters. Here’s my understanding, It’s assumed that X% of released fish die at certain temperatures. So in May water temps will range from 55 – 62 degrees, I think that will be about a 1% mortality rate. 300,000 pounds of fish could get caught this May (wild guess) 300,000 x 1% = 3000 pounds hooking mortality. It don’t know if this is calculated daily or what. When I get a chance I’ll get specifics and pass them on.
The reason we went backwards from last year was the total biomass estimate decreased ~10%. 120,000 pounds of fish were harvested, some died naturally, and the fish are probably slightly lighter than last year. But the 2023 year class was a bust, the juveniles were small and skinny in Oct. Their chances of survival is low. Nothing replaced those harvested fish. I don’t expect to see biomass increase for one more year when the 2021 and 2022 year classes start putting on weight and influencing the population.