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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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
Our friends at Wild Steelhead Coalition provide this new report. "We teamed up with retired WDFW scientist Dick Burge to examine how CnR handling practices can impact mortality levels and the potential steroid-hormone changes in fish that damages eggs and fry development." Click here to open flip book.