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FINSIGHTS- TRANSLATING THE SCIENCE OF FISHERIES REPORTS #7

Finsights #7 – “I saw the fish swim away so it must be fine” - Part 3

Finsights #7  Robert Lennox Photo

Finsights #7 Robert Lennox Photo

My last two posts have been about the range of possible lethal and sublethal impacts of catch and release angling on fish, and I want to round out the discussion with one last post. When it comes to sublethal effects, it’s fairly easy to comprehend the direct consequences of angling on an individual fish. What can be more difficult to understand and discern scientifically is how angling could impact an entire population of fish.

One way to get at population level effects is to examine how angling impacts the fitness of fish. Keepemwet Science Ambassador John McMillan recently provided a nice explanation of what fitness means for fish - the ability of an individual to contribute viable offspring to the next generation.  So, a decrease in fitness would be a decrease in the number or the quality of offspring from a given fish.

Anglers landing an Atlantic salmon. Robert Lennox photo.

Anglers landing an Atlantic salmon. Robert Lennox photo.

A scientist releasing a studied fish. Robert Lennox photo.

A scientist releasing a studied fish. Robert Lennox photo.

The research paper for this blog post specifically looked at whether catch and release angling impairs fitness. The scientists were able to take advantage of the unique geography of a small river in Quebec, Canada that also contained a fish ladder, which allowed for a complete inventory of Atlantic salmon that entered the river to spawn. Every fish that entered the river was sampled for their genetic makeup. Genetic samples of fish are most frequently obtained by cutting off or punching out a very small piece of fin (it doesn’t bleed and quickly grows back).  

Atlantic salmon in the river. Robert Lennox photo.

Atlantic salmon in the river. Robert Lennox photo.

What did they do?
    •    All salmon entering the river at a fish ladder were genetically sampled and their length measured.
    •    All anglers on the river were asked to fill out a questionnaire and take a genetic sample of each fish they caught and released.
    •    The following year, fry (baby salmon) were sampled in the river to determine parentage.

What did they find?
    •    20% of the salmon in the river were angled and were the parents of 22% of the offspring. This means that the fish that were caught and released were able to spawn.
    •    Larger angled salmon produced significantly fewer offspring than non-angled salmon, however, there was no difference in number of offspring (in angled vs. non-angled fish) for smaller salmon.
    •    Air exposure decreased the fitness of salmon.  Depending on water temperature, the reproductive success was 2 to 3 times lower for angled salmon that were air exposed versus those that were not.  

Why is this study important to anglers?
    •    Once again, we see that air exposure is bad for fish. In this case, it’s bad for the next generation of fish.  
    •    All fish are not equal – larger fish can be more susceptible to the sublethal effects of angling. This is true when it comes to fitness, as well as when it comes to stress (link to Finsights #4). As anglers, we need to treat the larger fish that we pursue with the utmost care and respect.  Angling can impact large fish in more ways than it does smaller fish and therefore we have an extra duty to Keepemwet.

Link to full research paper.

Happy Fishing!
Sascha Clark Danylchuk

 

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SCIENCE NOTES FROM JOHN MCMILLAN

Wild steelhead image from Keepemwet Science Ambassador John McMillan.

Wild steelhead image from Keepemwet Science Ambassador John McMillan.

Fitness. I bet you have heard the term if you love #steelhead and #salmon, particularly if you pay attention to research on hatchery and wild fish. Studies that compare the performance of hatchery and wild steelhead often measure fitness. So what does it mean? Well, in this case it doesn’t exactly refer the physical fitness most of us think about on a day to day basis. It’s not about how far or fast we can run, nor about how strong or tough we are. In fact, it has very little to do with that concept because it really only considers physical aspects and does not incorporate a mental or learning aspect, nor does it account for luck or chance. Rather, fitness in evolutionary biology is the measure of an individual’s ability to survive and reproduce offspring. In studies of steelhead, and other salmonids, the measure of fitness is often described as an individual’s contribution to the next generation. It is a sum measure of survival at different life stages, such as from egg-to-fry, fry-to-parr, parr-to-smolt, and smolt-to-adult. Basically, individuals with higher fitness do a better job of producing offspring relative to other members of the population. Individuals with lower fitness do not do as well. While many studies have compared the fitness of wild and hatchery salmonids, the term is also important to understanding the value of diversity. If you recall, I have previously posted about the remarkable number of life histories that steelhead display. The diversity helps dampen annual fluctuations in populations relative to species with fewer life histories. Why? Because some life histories life histories perform better – aka., have higher fitness – in some years and places than others. Maybe the wild steelhead in this photo will be one of the few that passes along its genes to the next generation, and if so, it might have nothing to do with how fast or strong it is. It may come down to something like nest site selection, or maybe even chance. #fishing#flyfishing #wildsteelhead #biology #science#rivers  #spey #conservation#pnwwonderland #uwphoto #snorkel

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Science Notes from John McMillan

Chrome steelhead via John McMillan Instagram @rainforest_steel.

Chrome steelhead via John McMillan Instagram @rainforest_steel.

One of the great aspects of Instagram is meeting a number of people who share a similar interest in #fish, #rivers, and #fisheries. I was fortunate to be raised with a father, who very early on, promoted best handling practices for catch and release of #wildsteelhead and other #salmon and #trout we released. We also promoted the wood shampoo for those fish we kept and ate. But as our fish populations decline and opportunities for #fishing for #steelhead and salmon also decrease, we are faced with increasing pressure in fewer fisheries. To effectively share the resource, anglers have largely shifted to releasing wild steelhead. And over the past decade there has been a dramatic increase in implementing best handling practices to try and minimize our impacts. We love to catch the fish, and that comes with some cost to the animal. Nonetheless, the way we treat the fish is important because it can reduce stress and improve chances that the fish recovers from the experience more quickly and with less physiological impact. This is one reason I completely support the @keepemwetfishing movement, and why I felt honored when Bryan Huskey asked if I was interested in being an Ambassador. I feel privileged to be included with such a strong group of anglers, photographers, advocates and scientists. I understand some anglers eschew #keepemwet, and I am not here to take offense. I am not above anyone, we are all anglers. Yet, I would also ask that all anglers consider their handling practices. Recent research on Atlantic salmon found that even short amounts of air exposure (< 10 seconds) had some negative effects on reproduction. It is but one study, but studies on other species have also found effects of air exposure on physiology and survival. Regardless, we don't exactly understand the full effects, perhaps they are less, perhaps more. More importantly, if we want these fish to not only survive, but recover quickly and hopefully in the case of steelhead -- return to spawn again -- I don't see a tremendous inconvenience in keeping most of the fish in the water. After all, it is us who will benefit. #flyfishing #spey #handlefishwell #speynation #flyfish

Coho salmon eyeballing a hatchery steelhead via John McMillan Instagram @rainforest_steel

What is wrong with a #hatcherysteelhead that came from two #wildsteelhead parents? A recent study addressed this question. Scientists from Oregon State University mated two wild #steelhead and reared the offspring in the hatchery. After only one year, 723 genes were differentially expressed in the hatchery steelhead. The differences were related to wound healing, immunity function and metabolism. This indicates that steelhead adapt rapidly to the conditions in hatcheries, and a potential cause is the high density of fish.

For example, changes in wound healing and immunity function could prove beneficial when tens of thousands of juveniles are crammed into a small raceway competing for food and space. It may help alleviate fungal infections and other issues caused by the constant nipping and biting that arises in such situations. The same goes for metabolism. Steelhead and other salmon with faster metabolisms are more aggressive. More aggressive fish do better in hatcheries because they obtain more food and grow faster than their cohorts with slower metabolisms. Larger smolts survive much better than smaller ones.

So, why would selecting for a faster metabolism be bad? It's not, if you live in a hatchery. But if you live in nature, it can be a detriment. Food is typically limited in nature, so those ultra-aggressive individuals may do well during the rare years when food is really abundant and competition is high, but they are likely to suffer increased mortality in most years when food supplies are normative – they may starve or be killed by predators because they have to take too many risks to meet their caloric requirements. Hard to focus on hiding in a log-jam when the belly is screaming, Feed Me! The worst part: we now know the genetic changes that helped them survive in the hatchery are passed to their offspring that will live in nature, and hence, this is one reason hatchery steelhead – even those from wild parents – survive poorly compared to wild fish. #science #ecology #biology #fishing #flyfishing #uwphoto #snorkel #underwaterphotography #spey #keepemwet

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