So what is the long range difference between over harvest and poor ocean conditions, with respect to stock populations?
When ocean conditions are poor, stock abundance ramps down, but when ocean conditions are good, they ramp back up.
So if over harvest is really happening, then curtailing harvest would have a similar effect as good ocean conditions do, and we should see stocks rebound.

In the past, most of the fish that survived to adulthood spawned. In years of poor ocean conditions, at least some of them made it back. In good years, even more did.

What we do now is knock the run down a little on bad years and a lot on good years. This gets complicated by our desire to fish Chinook and coho before we have any idea of the run.

And, what do we do with ocean fisheries? The last few years we model a season. Then, when catches don't materialize we increase the limits and days fished.

Ocean "conditions" are pretty variable, too. Some Oregon researchers came up with a great model to describe OR coho. Used 4 separate ocean measures to explain survival. The problem was that the 4 factors were not necessarily related. The first 3 could be good but when the 4th came in it was bad; hence a low run. The reverse happened, too. It looks like good and bad things can happen over the whole marine time; any one can kill the run and any one can bring a good return.

I will touch Chinook only as several others here will do others more justice. When you MSY fish you are in reality flat lining a run or species. In nature you can have floods, low flows, all which limit and impact runs but with time a year with good river and ocean will come around on the low side and nature brings it back up to the naturally sustaining level of the others.

Second in the case of ocean fisheries they are the primary cause as of the loss off 5 & 6 age groups which are the big guys in the pictures. Longer in the ocean, a smaller % of the run, most extreme harvest pressure and few remain in WA. Take the Elwha, when the dams are gone most stocks should recover at a reasonable rate but not Chinook. The Alaska & BC ( and tribal & US sport ) will continue to maintain the pressure that reduced Chinook in the state to 3 & 4 yr age groups and the genetic loss will not be reversed.

Over harvest and just as importantly how & where it takes place has a dramatic impact on Chinook. It differs say from the Columbia to PS but it is always present and the effects are as long tern genetically as hatchery practices and habitat loss. It is a invisible process of genetic attrition that one sees only through the eyes of history. My father caught 40, 50 & 60 lb Chinook on the Satsop when I was 6 yrs old ( yes AM that is 56 yrs ago ) now the population is 3 & 4 yr classes and few get above 30. We like to scream dirty tribes & gillnetters, truth is the real driver was and is the ocean commercial and sport. Chinook never could, nor will be able to genetically sustain the level of ocean intercept fisheries applied to them.

So why are some wild steelhead stocks healthy enough to allow limited harvest, yet the larger percentage of remaining PNW stocks are in poor condition?
This is in spite of the fact that most of these stocks have no commercial or sport harvest, and this is after over 25 years.
This seems to indicate other factors might be limiting these populations.

We may have reduced harvests on wild steelhead, but I don't think there are any of the major river systems that have zero harvest. Also, every steelhead killed this year reduces next year's run by the loss of repeat spawners.

Steelhead are, i believe, a "marginal" species in that a lot has to go right for them to do well; a lot like rockfish. We have eliminated the early retruning fish, reduced access to tributaries, removed rpeat spawners, lowered stream productivity, and wonder why they don't recover.

An interesting outcome of a study of teh switch that make3s resodent/anadromous is that higher summer flows with lower temperatures produce residents. So what do we do on regulated rivers?
Increase summer/fall flows for salmon spawning and to maintain rearing area. This water will come from the depths of teh reservoirs, so it's colder. Folks studying streams with these mandated flows tell me the salmon are responding fine; but not the steelhead.

Part of our problem is that too many folks think a steelhead is nothing more than a spring spawning salmon and all the same rules apply.

I assumed you were talking salmon as steelhead is another thing altogether. In fact they are the most out of place fish in the PNW as they are total takers from a watershed, by that I mean a Chum takes little as it is to the ocean right out of the box. Steelies by their life cycle contribute almost zero to a watershed but take everything from it. As a total taker when things get out of balance they are vulnerable. The other thing is frankly in the world of fin to fin combat Steelies are pussy's. You may think they are majestic but they are wimps. Much like the Bald Eagle, our national bird, which is a opportunistic creature that can get its ass kicked by crows, Steelies can not adapt to much at all let alone rapidly.

I have watched Bio's ( several on this BB ) argue this / that from many perspectives. Want to know my thoughts? Clueless is my thoughts. Nature created a system that salmonids created their own ecosystem by the fact they went to the ocean and returned to fertilize the home that would be for future production. From the minute harvest began to remove large scale numbers of salmon from the cycle production declined. Go to historical records and see what natural production was BEFORE Grand Coulee. Look to what harvest was and had become, then come to grips with the fact that prior to WWII and the dams habitat was not impacted that much. Eastern WA & OR were regarded as wilderness! In the 30's in GH they panicked as they reduced harvest due to declining runs. Logging, farming, cities, and fish were in decline. BS as all had impacts to be sure but it was not until the 70's ( after Columbus Day and the start of export ) in GH that timber really nailed fish. Then add tree farms on 40 year rotations and it was hyper drive habitat impacts.

You know what? The damage was already done with harvest and massive ocean harvest finished things off. Right now at this point in time ALL THAT IS HAPPENING is the impacts of the over harvest and population expansion starting in the 70's is coming full circle. Outside the Columbia it will get worse as I don't think PS is going to come out of it and the coast is 15 years out before the impacts of tree farms 40 yr rotation come full circle.

I am an old fart and seen to many battles lost for fish but irregardless it is what it is.

Bad oceans conditions take a significant number of potential spawners out of the population, harvest can potentially take out a significant number of potential spawners.
Yet when ocean conditions improve, so do stock populations, but with curtailed harvest, little if any stock recovery is seen.
This theory can be seen in action on the CR.

Headed for the Lady in Red. Your looking at a time frame that is narrow by natures terms. You need to look at 15 to 20 life cycles of the creature. Your point is well taken and was mine until CM and PS made me look to the time thing and out of the present and human terms.

Your stuck in your view of time in human terms rather than natures, and your going to be be very disappointed. As to the CR nothing is natural. Dams, irrigation, cities, all have altered things ( and the power dams and people are going no place ) so that nothing mirrors the natural processes other than the act of reproduction, and that is limited.

The simple fact is salmonids and modern human society are incompatible. It is only a question of how many natural spawning populations will remain 100 years from now that is in doubt. What is not in doubt is that very few will remain and mixed stock ocean harvest will no longer exist.

I have witnessed several ocean condition down turns, in each in every case stocks that were struggling to maintain a population, rebounded in just a few years of favorable ocean conditions.
Harvest curtailment has little to no effect on these same stocks.
And as for the CR, what about the LCR stocks? They don't have to negotiate the dam maze, yet their populations are low, and this is spite of no harvest.

I think NOAA is getting alot better at estimating ocean stocks than they were 10 or 20 years ago. But you still have to factor in hook mortalitys, high grading and a constantly moving mixed stock fishery. Ocean conditions affect crab shrimp whiting and just about every other short life cycled fish out there..

In river hook and liners have a very small impact on over all populations, and their impacts are even smaller in a C&R fishery.
Isn't that why CCA is lobbying for selective commercial harvest?
To do what sports can not, and that is remove more hatchery fish from the system.

Freespool,

Both over-harvest and poor ocean conditions contribute to reduced survival, that is, fewer recruits returning from the ocean, or even the rivers themselves in the case of in-river harvest, to be part of the spawning escapement. The significant difference between over-harvest and ocean conditions is that we have the ability to influence harvest, but we can't significantly affect ocean survival conditions.

Your point about the CR is a different kind of example where it appears that harvest is having little effect on recruitment, whereas ocean conditions have a major effect. Let me remind you that passage conditions at dams, or the lack thereof, is a form of harvest (i.e. human induced mortality to fish). In some years the dams harvest a far greater proportion of the runs than do the ocean and in-river fisheries. Reducing dam harvest mortality has the same effect as having a high ocean survival cycle.

The upshot is that many variables are capable of being the limiting factor for fish populations. Which factor for any given species and cohort year varies and continues to keep the subject complex and elusive of any simple explanations.

Sg

My question is why do stocks rebound quickly when ocean conditions improve, but respond slowly, or not at all when harvest is curtailed?

Salmo nailed it. Sam Wright tried to get folks to consider all human-induced mortality as "harvest".

Start with eggs. Before all the sediment was introduced to streams, egg-fry survival maybe have been 50-60% or more. Maybe like what is seen in a a spawning channel. Move ahead to Chinook; a popular fish that makes little long-term use of FW. If egg-fry now is in the 10-20% range due to sediment in the gravel then we are putting something like one third the smolts out. So, instead of harvest, we take that mortality as logging, roads, or other sediment movers. Factor in the loss of fish due to use of water for non-stream uses. We keep making choices, and the generally come at the expense of natural resources.

Freespool,

When harvest is the limiting factor, populations do respond quickly as soon as the over-fishing is discontinued. For instance, as soon as spring spill is used instead of no spill and forcing smolts to use turbine passage or barging, fish populations respond with higher survival due to, duh!, lower mortalities.

Carcassman,

I cannot be certain, but I think egg to fry at 50+% even in pristine times is unrealistically high. The best I've been able to estimate is 30-36%, but that is much better than the 12% or less that has become common for many salmon in contemporary times. The proof is in the evidence that many wild coho and chinook populations used to be able to sustain harvest rates of 75 and 80%. Now we have a lot of populations that cannot sustain 40% and even less. Clearly the survival rates at several life stages are reduced from former times.

Sg

Just did an interesting test, I cut 100 pieces of small paper about an inch square. 50 I marked W and 50 I marked H, I then put them in a small plastic grocery bag and shook them up.. I then did a blind grab one at a time, I kept each H and put each W back intill I reached 50 times..If these were coho and I handled 50% of the run I would have kept 14 and with a 22% mortality rate I would have killed 8 wild..I'll try it again in the morning a few times to see if it changes much..

Salmo, I've read hundreds of stock assessment surveys, I can't recall ever seeing over harvest as a limiting factor for recovery.
However, water quality, poor stream complexity, no large woody debris recruitment, poor over wintering back channel/alcove habitat, and poor estuary habitat are listed in almost everyone.

A huge factor that is often ignored is the impact that ocean survival has on various population parameters. During periods of poor ocean survival measures such as carry capacity and MSY levels for a given basin/population are reduced - marginal habitats no longer producing enough smolts to replace spawners. This of course increases the likely of over harvest.

Freespool -
the answer to your question -

"My question is why do stocks rebound quickly when ocean conditions improve, but respond slowly, or not at all when harvest is curtailed?"

is that in those situations the quality of the freshwater is such a dominate factor that it often over shadows the harvest reduction. The two big factors at play in your example is the carry capacity and production parameters of the population.

If historically the carry capacity of system could be symbolized as a gallon jug the population productivity would be how quickly that jug would refill from low spawner abundance - historically that could visualized as the water tap wide open. That gallon jug would refill quickly; in the real world depressed populations would respond within a generation to a condition near full seeding -what ever spawners reach the gravel produce large number of smolts.

Contrast to the situation we now see on many of degraded system. Instead of a gallon carrying capacity they often have only a pint or is some cases a cup for a capacity. Even more important is that their population has been also been greatly reduced. To condition this example the productivity wouold be just drips from the facet; meaning that even though the capacity is a pint it will take a longer to refill. The result is the it takes a long time (generations) for a population to respond from a depressed conditions -those spawners reaching the gravel are producing very few smolts.

When marine survival increases; let's say it doubles those limited numbers of smolts being produced in the degraded system do twice as well leading to larger runs. Of course the next generation doesn't benefit as much as we would think due to the reduced productivity of the population/habitat. All of this of course is why so many of us continually harp on the freshwater habitat conditions as key even though harvest and other factors can be important.

Tight lines
Curt

Ok FS lets try it another way. You don't see harvest in limiting factors because it was not politically acceptable to be put in when the great collapse came, this time. Second, THEIR WAS NO MONEY TO BE MADE in reducing harvest levels and locations. The so called Salmon Restoration biz with the grants, staffs, studies, that puts more money in the trough. Nobody in the government policy levels had the balls to take the issue on. One guy I know did and after a Sen screamed he got skinned and parked, right now. Another thing is this. Where stocks go in the marine environment differs. OR & WA have switched stocks and other things in this N / S turning to get away from the others ocean harvest and it impacts different streams differently.

Another is well take PS Chinook. Say tomorrow all hatcheries closed and it is now 4 years later. What happens? With no hatchery fish in the pool and now only wild, marine harvest ends. Tribal terminal will continue .............. sorta. You see AK & BC would fish on and now as we have only wild in the pool the impacts would be massive. No fisheries in PS other than terminal and many fisheries for other fall salmon would be curtailed due to lack of numbers to survive hooking mortality. In the end the loss of hatchery Chinook would be the worse thing to happen to the wild populations in PS and pretty much end non tribal harvest. ( that includes C&R )

This strange tale of harvest your looking at is a trail from AK to CA and huge parts are never seen. As to data, outside the C, it is about as accurate as the 3 week weather forecast.

Thanks Curt, your explanation seems to be what most independent fisheries scientists have been saying for decades.
The deciding factors for stock populations are ocean conditions and a river's carrying capacity.
Without these two factors working in conjunction of one another, stocks crash.