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The Mathematics of Catch and Release

Chinook Mortality- Help me… I was never good at math

Disclaimer: this is lacking proficient calculation, scientific fact and likely intelligence. It is however heavy on opinion…mine.

I recently had the pleasure of observing a meeting of the Sportfish Advisory Committee in Smithers. DFO head office was on conference call while local representatives made the journey down the block. The agenda was the closure of Skeena drainage chinook fishing for 2018 including all the tributaries. The bottom line is that things don’t look great and we need to cut pressure.

The views in the room varied from willingness to harvest only jacks, to saltwater lodges take too many, to marine anglers in Rupert are to blame, to first nations sustenance is the problem and finally to total refusal to give up a full retention fishery. The soldiers were firmly in their trenches. DFO didn’t seem interested in entertaining too much beyond everyone needs to bend and in river anglers will likely be hit the hardest.

So how about catch and release? Doesn’t it work? Isn’t it an option? Well just as I was daydreaming the possibility an informed that catch and release can’t even be entertained because it’s so lethal. In fact as many as 38% die, he pronounced.  Okay, I’ll drink the Kool-Aid. 

Here is where I need help with my math. So lets just assume catch and release mortality is 38% across the board for chinooks (it’s not), I pose a few questions:

1) what is the mortality of fish in a retention fishery? That is if I kill one what are the chances it dies?

2) How would the number of anglers compare in the river impacting chinook during a catch and release fishery?

3) Grade 3 math problem. 100% vs 38%. Difference? Not horribly relevant but..

4) Which mortality rate has less impact 100% or 38%?

So my answers:

  1. I think that if I bonk a chinook salmon there is a 100% chance it dies.
  2. I think there would be less. A lot less.
  3. 62%. I used a calculator.
  4. I believe 38% has less impact.

Above: An example of a chinook salmon with a 38% chance of catch and release mortality.

The Closure

So I fully understand that in times of low abundance trying to minimize impacts on returning stocks is vital. I also understand that after conservation DFO is mandated to allow for first nations sustenance fisheries and fully accept that. This might be the year to put the tackle away but forever onwards the only choices are  harvest or closure?

I have a difficult time understanding how DFO doesn’t employ catch and release as a tool to minimize impacts on returning stocks. The bartering system the Department rolled out the meeting was just a game of allocation numbers and surely a decreased C&R mortality could enter the arena. How is there no middle ground between killing everything and not fishing? Imagine sitting through a population biology lecture where reducing mortality by 60%+ wouldn’t be considered.

Now I understand the argument that as an angling guide I’m just pushing for access to fish on years that the river would be otherwise closed. But I would phrase the argument another way. As a guide I’m looking for access with less impact even on years of abundance. This means that employing catch and release may allow angling during periods of lower abundance but also during periods of greater abundance where ramming through the normal harvest fishery for the fist pounders might prove too costly. This is another option.

With the prospects of leaner times ahead I’d like the option to go fishing even if I can’t harvest fish. As a fishing guide I’d like the option to take anglers to the river to fish for chinooks even if we have to let them go. The process can’t be high jacked over the fears of a slippery slope.

Back to my simple math. If less fish die, more fish spawn. If more fish spawn then anglers have more access.