For decades managers have been scaling back fisheries without successfully recovering local salmon runs. Our simulation will show you why this hasn’t worked, and let you learn for yourself what will.
For about as long as we can remember, the conventional wisdom has been “Fishing must be cut to help recover struggling salmon stocks.” This argument seems sensible, appealing and obvious– which is a big part of why it’s so frequently presented. But the truth of the matter is that this position is dead wrong in the most important cases we face in Puget Sound and around the state. The arguments to cutback fishing are so seductive that even sportfishing advocates can be fooled by this Jedi Mind Trick. Instead, we believe that Washington State selective fisheries have been remarkably well designed in recent years, and are not a significant factor limiting the recovery of threatened stocks in the state. Cutting these fisheries will not in any credible way help recover salmon stocks — and will likely lead to a revenue spiral for WDFW, a net negative for fish.
Sounds crazy to some of you, right? Please give us 5 minutes more to convince you…
To understand why we say this, we’ve constructed a simulation of a salmon population for you to try out our assertions for yourself. We’ve invented a fictitious river called the “Simulguamish” river — with characteristics not that different from our local Stillaguamish River. Your goal is to recover the population to 20,000 fish (half the Stillaguamish historical highs). Adjust the sliders yourself and see if you can recover the salmon populations by curtailing fishing… We hope this exercise will help develop your intuition for what the real source of our salmon recovery problems are (hint: it’s not fishing).
Simulation notes: The underlying mathematics of our simulation is the Ricker Model, a longtime standard in fisheries management, and one of the important modeling tools used to develop the most recent 10-year Puget Sound Chinook Harvest Management Plan (PSCHMP). While the Ricker Model is a relatively simple paradigm, it is helpful at fostering a clear understanding of the key relationshps driving salmon abundances & recovery.
Simulguamish River | Simulation
To define terms — our Fishing Rate slider is what biologists and fishery managers call the Exploitation Rate (or ER). Simply put that is the percentage of the adult fish which are caught and kept, as well as any unintended mortalities resulting from fisheries (recreational, commercial and tribal). As a default we use the PSCHMP Stillaguamish target of 24% total ER, which includes the intercept fisheries in BC (16%) and all Washington State fisheries (8%).
The Marine Predation slider is really similar to the Fishing Rate slider — except of course that we’re modeling predation from harbor seals, orcas and other marine mammals as well as sea-birds. Since some of this predation occurs on out-migrating smolts and juvenile salmon — those mortalities are adjusted into what is known as “adult equivalent” values (or AEQ). The AEQ approach recognizes that if juvenile salmon only have a 1 in 10 chance of returning as an adult due to ocean conditions, then a harbor seal chomping on 20 juveniles is equivalent to an orca eating 2 mature returning adult fish. In the end, this is just nature’s own Exploitation Rate. We hear all the time how the problem in Puget Sound is Harbor Seal predation–but we don’t believe it’s blocking recovery. Experiment with the sliders and decide for yourself!
Which brings us to the River Carrying Capacity — that’s the maximum population of fish that the environment can sustain indefinitely, given the food, habitat, and other necessities available. If you spend time experimenting with the simulation, you’ll quickly realize that it is in fact the river carrying capacity that is the prime driver for the salmon population. We encourage you to reset the carrying capacity to about 740 fish (matching the best-fit carrying capacity of the Stillaguamish river currently) and drive both fishing and predation down to zero, and see if the run recovers. Nope! Because zero fishing and zero marine predation won’t recover the rivers unless you increase the Carrying Capacity of the river itself–the habitat is where we must look for recovery.1
Finally we’ve included a Conservation Hatchery toggle switch which allows you to see how vital this facility is on a river like the Sillaguamish. Our simplified conservation hatchery adds a fixed number of 1000 adult fish/recruits to each generation. Like the Natural Origin fish spawning in the river, these fish undergo marine predation and fishing impacts in our simulation. If you try turning off the Conservation Hatchery under current conditions (use [Reset] if you’ve been trying the sliders), you will see the run quickly collapse. It’s an essential facility under current conditions!
Making Sense Of This All
For a lot of people, it is difficult to understand why the elimination of fishing and predation will not lead to recovery… It even seems at times policymakers get thrown off by technical terms like “Rebuilding Exploitation Rates” which, confusingly, do not (and have not) lead to the rebuilding of Puget Sound stocks. Those Rebuilding ER’s can’t rebuild our runs because as you’ve now seen, fishing isn’t the problem — the river Carrying Capacity is the problem.
So we want you to all become experts at helping explain why the recovery solution lies in the river habitat, not fisheries management. In particular, it’s vital that we recognize how different salmon are from endangered mammals and birds the public is accustomed to talking about. It’s important to point out that stories and lessons learned on recovery those endangered species are at odds our efforts to make good decisions recovering salmon runs. Let’s highlight some details:
The first critical difference between salmon and typical Endangered Species (Spotted Owls, Orca and Bald Eagles) is that salmon reproduce only once before dying. Biologists call this behavior semelparity, and it dramatically changes the approach we must take to foster recovery. It’s obvious but bears attention that all returning adult salmon die regardless of if they are caught by fishermen, eaten by marine mammals or survive to spawn. This is profoundly different than the birds and mammals we interact with on a regular basis. Saving a salmon from a fisherman’s net will impede the salmon from spawning once. On the other hand, saving an orca entangled in a ghost net could allow that individual to live and reproduce for the next 30 years. In these more commonly publicized ESA recovery cases, protecting the breeding adults from harm is often the most important conservation measure–but in Salmon recovery the key is typically the health and survival of the eggs/fry/smolt.
The second and related difference between Salmon and more commonly discussed Endangered Species is the large quantity of fertilized eggs produced by spawning adults. A single pair of spawning salmon may produce 3-4000 fertilized eggs. With reasonable habitat and ocean conditions it’s not unheard of for that single pair to produce 20+ adults returning to the spawning grounds 3-4 years later.
This incredible reproductive resilience means that a small number of salmon are readily able to rebuild a substantial run of fish — provided they have sufficient good habitat to spawn in. Unfortunately, in all the important/threatened local runs of Salmon, we find terrible river conditions for those fertilized eggs. A combination of high sediment loads (logging/landslides), high water temperatures, increasingly frequent flood events (development/impervious surfaces), obstructions (culverts/dams), and urban pollutants conspire to make the rivers tough places for eggs and fry to survive. Returning more salmon won’t help this–they will simply not find places where they can spawn successfully.
And in all fairness, we should tip our cap to our co-managers, the Northwest Indian Tribes. They have been right on this habitat point for decades. We disagree with them on a number of big issues — but their position on the link between habitat and recovery is unimpeachable.
Does This Excuse Unlimited Fishing?
Of course it doesn’t. Surely someone on social media or the comments section will claim we think we can fish our way to recovery. That’s baloney, and you know it as well as we do. We are well aware that overfishing can destroy runs. Our points are simple:
- Recent Puget Sound selective fisheries have been well designed and are demonstrably not overfishing our runs. Our stagnant/declining runs are demonstrating acute problems in the habitat. We must educate policy makers and conservation groups about these realities.
- Co-managers and governmental agencies (hello NMFS and NOAA) need to call a spade a spade and admit the actual cause of our problems lies in the rivers. Then get to the expensive and difficult work of real-recovery — river habitat restoration.
- Further curtailing fishing will weaken WDFW revenues — meaning less personnel and science available to spearhead the habitat/carrying capacity recovery we so desperately need.
- All user groups can and should continue to look for ways to further improve their selectivity–especially those groups which have resisted these modernizations (looking at you, gillnetters over ESA runs).
- Technical Note: At low carrying capacities, our Ricker values for A (productivity) & B (density dependent) are based on an FSA fit of Stillaguamish NOR spawner/recruit data from 1990-2009. This fit puts A at about 1.5. At high carrying capacities, we interpolate A upwards to a maximum of 5, and solve B for the desired carrying capacity. All Ricker computations have a random +/- 10% added to make some affordance for natural variation.