2024/25 Halibut Stock Assessment

searun

Well-Known Member
The IPHC released the 2024/25 stock assessment on Dec 19th. Here's the link: https://www.iphc.int/uploads/2024/12/IPHC-2025-SA-01.pdf

My quick read is the management actions in last few seasons where we took some fairly aggressive reductions in fishery intensity are slowly paying off, against a back drop of 2 recruitment age class groups that are starting to dominate our fisheries (2012 & 2016). There is a very slight up tick in spawning biomass.

IMO it seems that it is likely this upcoming IPHC will probably land on status quo at best, or possibly another reduction in the overall fishable TAC to ensure the increasing biomass trend continues. Can also see the IPHC taking a wait and see how these 2 dominant age class groups perform in the fishery and if there are other good recruitment years coming up behind those to ensure there is sufficient recovery in abundance. If you look at the historic trend we are still at very low productivity and spawning abundance levels. Still concerning is we continue to teeter just above the 30% trigger point (currently only 8% above) where there would be reductions in fishing intensity to avoid declines down to the 20% level where all fisheries are closed.

Some highlights:

The IPHC’s interim management procedure uses a relative spawning biomass of 30% as a fishery trigger, reducing the reference fishing intensity if relative spawning biomass decreases further toward a limit reference point at 20%, where directed fishing is halted due to the critically low biomass condition.

The relative spawning biomass at the beginning of 2024 was estimated to be 38%**(credible interval: 18-55%), slightly higher than the estimate for 2023 (37%).

** Note - 8% above fishery trigger to reduce fishing intensity.

Fishing mortality from all sources in 2024 was estimated to be down 5% from 2023.

Note: resulting decrease in catches/removals related to management measures to reduce fishing intensity

The 2024 modelled Fishery-Independent Set line Survey (FISS; see IPHC2025-AM101-09 and ) detailed a coast wide aggregate Numbers-Per-Unit-Effort (NPUE) which increased by 3% from 2023 to 2024

The modelled coast wide FISS Weight-Per-Unit-Effort (WPUE) of legal (O32) Pacific halibut, the most comparable metric to observed commercial fishery catch rates, decreased by 9% from 2023 to 2024.

Note: this indicates smaller younger age class fish starting to dominate fishery, and older larger fish are aging out of fishery

Biological information (ages and lengths) from both the commercial fishery and FISS shows the continuing shift from the previously dominant 2005 year-class to the 2012 cohort (12years old in 2024) and now the 2016 cohort (8 years old in 2024).

The results of the 2024 stock assessment indicate that the Pacific halibut stock declined continuously from the late 1990s to around 2012.

The spawning biomass (SB) is estimated to have increased gradually to 2016, and then decreased to a low of 145 million pounds (~65,700 t) at the beginning of 2024. At the beginning of 2025, the spawning biomass is estimated to be 149 million pounds(67,500 t) with an approximate 95% credible interval ranging from 97 to 216 million pounds(~44,100-98,200 t).

NOTE - older larger age classes are aging out of fishery being replaced by smaller sized 2012 and now 2016 more abundant age class recruits into the fishery - good news is slowly seeing very small increases in spawning biomass resulting from lower fishing intensity

Based on age data through 2024, this assessment estimates that the 2012 and 2016 year-classes are currently the most important in the fishery and survey catches but are only near average when compared to the preceding 15 years.

Note: basically average recruitments, so not going to result in a significant increase in spawning abundance longer term without more substantial new recruit age class groups coming up behind these 2 age class groups


Biological information (ages and lengths) from the commercial fishery landings showed that in 2024 the 2012 year-class (now 12 years old) was again the largest coast wide contributor (in number) to the fish landed. This follows the same patterns observed in 2022-23, after the fishery transitioned from the previously most-abundant 2005 year-class. The FISS also observed the 2012 year-class as a large proportion of the total catch, but the largest proportion comprised the 2016 year-class (age-8 in 2024) also observed in the commercial fishery and recent recreational fisheries.

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Any insight/theories on what drove the major increase in SB through 1980 to ~2000? Major decline obvious driver for our increased regs through early 2010s. Surprising to see the boom and bust of SB, especially when paired with the decreased fishery pressure.
 
Halibut are broadcast spawners. They spawn on the edges of the continental shelf and in deep gullies. Their larvae then move toward shallower coastal waters to begin early stages of growth.

They are largely dependent on ocean conditions to optimize spawning success, and particularly sensitive to changes in dissolved oxygen. Ocean conditions thought to be related to warming climate have not been kind to spawning success. Lower spawning recruitment contributes to the spawning biomass decreasing trends. In addition to poor spawning success, fishing intensity hasn't helped.

The largest factor in spawning success & biomass has been ocean conditions that support higher dissolved oxygen. In this lower recruitment regime the only lever we have control over that helps improve spawning biomass is lowering fishing intensity.
 
Update on stock assessment - new data now available due to late arriving commercial log books. Results of updated data show further decrease in estimates like WPUE. Looks like we could face further decrease in available TAC over last year's decrease. Decision table options look a little precautionary, but there isn't necessarily a strong relationship between number of spawners (spawning biomass) and recruitment success. In other words, more spawners doesn't always result in more successful spawning recruitment/abundance. But that said, this new data does show some risk of crossing the SB 20% (spawning biomass), which results in total closure of fishery. Very low risk, so will not be anything other than a risk consideration. Hoping the upcoming IPHC meeting leans towards status quo.
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Firstly, this is a coast wide fishery. So it's management should be guided by what works for the majority of fishers across the entire coast, not just areas within the coast. So agreed, we need to consider all fisheries equally. That said, based on the catch data the majority of effort (defined by catch) takes place June to September. If we are looking to try to satisfy the interests of the majority of anglers, the data does indeed point to protecting June to September as the core months. If we are getting down to very low available TAC to work with, hard choices should IMO revolve around satisfying the interests of the majority of anglers. I have to agree with Dale66, with exception that May doesn't appear to be as important as June to Sept by the numbers.

I fully appreciate there are some very important to some fisheries that take place in the early season. Notwithstanding, there are from my experience even more who value the late season in the fall to December - more so than early which is really only one geographic area fishery that benefits. Whereas, the fall fishery benefits a more broad geographic area that can (due to weather) get on the water to fish.

For what its worth, I have always tried to be guided by what choices provide the majority of anglers the most opportunity - or other way around, our choices should be guided by supporting those that satisfy the majority of participants interests.

Here's the ranking from 2019 season (pre-Covid) catch in pounds by month:

1. July = 336,520 lbs
2. Aug - 207,866
3. June - 152,282
4. Sept - 53,956.
5. May - 40,988
6. April - 10,259
7. Mar - 8,172
8. Oct - 834.....Note season closed Oct 9th this past season
 
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For contrast, here are the preliminary (not final) 2024 numbers by month:

1. 283,956. Aug
2. 244,259 July
3. 169,097. June
4. 60,144. May
5. 12,266. Apr
6. 6,867. Mar
7. 3,654. Feb

Note - I do not have the Sept and October numbers in the file. Past experience shows September is usually higher than May in many seasons, but not all. Certainly based on this data for 2024, the core months are June to Aug with outliers on the fringe likely to be either May or Sept
 
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