A REASONABLE AMOUNT OF SALMON

A reasonable amount of salmon is what we have been trying to achieve since 1991 when salmon were first listed as endangered. Salmon, by far, have to be one the most selfless creatures I may have come across. They spend their entire life working towards a single important moment, giving birth. All salmon leave their birthplace at a juvenile age to head to the ocean only to return a few years later to those same streams and rivers as their spawning grounds. Here’s an interesting fact, wild salmon always return to their birthplace after maturing in the ocean and as we see in the above picture some species of salmon change colors when they’re spawning. Their body color is silver when they’re in the ocean but once they return their faces are is blue/green and body is a pink/red color! They dodge predators, fight against water currents, and man-built obstacles such as dams, all for the purpose of giving back to their ecosystem. They’re like ninja fighters we see in movies who will do anything for their master, and in this case the environment.

Salmon face many dangers at various life stages. The Chinook salmon for example have the following life cycle:

                    

For the purpose of simplifying the stages a bit when there’s a mention of the term juvenile, it encompasses the alevin and fry stage. At all stages the salmon are vulnerable to both biotic and abiotic limiting factors. Limiting factors in this context mean anything that may affect the population size, the growth, and distribution of the salmon.  A few of the abiotic and biotic factors that salmon face are temperature, stream flows, predation and disease, and migration barriers.


REDD

First and foremost is the egg stage. Salmon eggs are found in streams/gravel beds. A redd (salmon egg) requires relatively cool water temperatures and high levels of dissolved oxygen. Soil erosion, due to extreme logging practices increases sedimentation which leads to rising water temperatures as the sediment absorbs the heat given off by the sun. This reduces the amount of dissolved oxygen in the streams. Other factors that lead to high water temperatures are low stream flows and removing vegetation from the stream bank.  Secondly, high stream flows or flooding can lead to scouring (washing away of gravel beds).

ALEVIN

The mortality rate for the salmon is during their transition from redd to alevin is great as predation by birds and insects reduces the survival rate majorly. Also, fungal infections lead to death of many.  Once the redd have developed into alevins, they are faced with similar limiting factors as at the redd stage, such as the presence of fine sediment. Fine sediment can suffocate the gravel beds by reducing dissolved oxygen and they prevent the young alevin’s movement out of the gravel beds.

FRY

At both the alevin and redd stage the salmon have a yolk sac attached to provide nutrition, but once they transition to the fry stage they become predators. Fry form territories in shallow pools and fight for their preferred habitats against other fry. At this stage the salmon require a healthy habitat with lots of vegetation as the number of predators increases. Abundant vegetation aids the fry in providing various hideouts from their predators.  Whereas increased sunlight can lower the oxygen concentrations, decreased sunlight due to reflective sediment leads to reduced aquatic plant growth. 


SMOLT

There are two limiting factors as the fry move into the estuary and become smolts. First being man made barriers such as dams and secondly natural barriers such as a dried up streams. At the smolt life stage the salmon go through a process known as smoltification. Smoltification causes physiological changes in the fish to help it to adapt to the salty ocean water at the later life stage. Smolts are found in estuaries. Estuaries provide food, shelter and growth to these fish. An unbalanced estuary habitat can lead to a very low survival rate for the adults moving out to the ocean as they develop.

ADULT SALMON

At adult stage once the salmon have entered the ocean they fall prey to various species despite their camouflaged outer layer. Their largest predator being, us, humans. Salmon have little to no defenses against human predation. Various salmon species spend a huge range of time out in the ocean. As for Chinook, they spend about 3-5 years. After this time period the salmon head back for the native streams, lakes, or rivers. Little is understood about the mechanism that leads these salmon back to their birthplaces, but it is believed that the use their chemical memory and the olfactory system to guide them back home.  They head back to the same estuary and go through smoltification in order to adjust to the freshwater.  Once again the health of the estuary is crucial to the survival of the adult salmon. The water temperature, salinity, and pollutant levels all play a role in determining whether an estuary is healthy or not. Once they begin to move upstream adult salmon face the biggest barrier of all, man-made dams.  Also, they fall prey to humans, otters and bears at this stage. 

SPAWNERS

Once they have reached their spawning site, the female salmon spend several days preparing a nest site which can be as large as nine feet. At this point we see some competition between females for a  healthy nest and between males for the females’ attention. The male, then, moves closest to the female to have the best odds at fertilizing eggs.

All this work and effort to return to the place they were born, just to reproduce?  Yes! and No! That is not all these salmon do, but reproducing is their grand, final, goal of life. As I said before they are the ninja fish who are here to give back to their master (the ecosystem), and that is exactly what they do. Soon after they have completed spawning, these salmon DIE! I know! Isn’t it a bit shocking and sad? Now you must be thinking how in the world are they going to give back to the ecosystem if they’re dead? Well they actually may have already given back, as many salmon become prey to other species. Yes! Salmon actually help feed around 40 different species in Alaska, alone. Also, if they were one of the lucky ones and survived their life cycle journey; by reproducing they will be providing more salmon for the bears, birds, seals, etc. Where ever there are healthy salmon runs, we find larger populations of other species as well. Particularly, brown bears to which salmon are a main source of food. Brown bears help fertilize terrestrial ecosystems by adding phosphorous to them which is retrieved from their salmon diet. Also, once these salmon die after reproducing, their carcasses provide nutrients and energy for the biota in that stream. Salmon during their lifecycle bring biomass and nutrients from the sea to the freshwater and terrestrial ecosystems.

So my question to you is WHY don’t we care about salmon? After all they have provided for us and the effort they put in to enrich our ecosystem. Why are they still present on the E.S.A. (Endangered Species Act) list? Why despite all the efforts and investments, that have gone into rebuilding or conserving salmon we are unable to return to the salmon populations as they were 20 years ago?

The answers to these questions lie right in the salmon life cycle. Now you must be thinking that the salmon being an essential food source for many is bound to be reduced in numbers. When, really predation by others apart from humans is just a small facet to this dilemma. The biggest reasons that salmon aren’t returning to their historical population sizes are the 4 H’s:  harvest, habitat, hydropower, and hatcheries.  All four of these factors are greatly influenced by humans. The growing population of our country and world has led to growing demands for food. Mass harvesting is one of the first reasons that led to endangerment of salmon. Secondly, habitat is greatly affected by our growing industries. Agriculture and logging practices affect the habitat for salmon and many other species. The deforestation has led to soil erosion which causes sedimentation in shallow pools and streams reducing the dissolved oxygen levels, which are fundamental for juvenile salmon survival. Also, the growing conventional agriculture practices have led to water contamination through pesticides which affects the salmon olfactory system which is critical for salmon to return to their native streams. Thirdly, the building of dams has greatly affected the ability of salmon to return home as many dams do not contain fish steps to help the fish migrate upstream. This causes death of many salmon before they are able to complete their life cycle and reproduce as they exhaust all their energy in trying to overcome this obstacle. Lastly, hatcheries which are believed to rebuild the salmon population are doing the opposite. The hatchery fish are genetically different from the wild salmon and unable to adapt to the natural habitat and if mating occurs between a wild and a hatchery fish, this significantly reduces the chances of those eggs to survive their life cycle and return to reproduce. So, though we believe we are increasing the chances of salmon eggs to survive by keeping them in controlled environments in hatcheries, we may actually be reducing their chances of survival. Not only that, we are putting the wild salmon populations at risk as well.

So, how do we fix this? Like much of the other arising environmental issues in our recent times. We must learn to consume less! I know it sounds so foreign, since we are bombarded with daily messages of how we should consume more and more. I feel like that’s how our generation is coming to be recognized, as consumers. Let’s put a stop to this MEME! In order to return the salmon to its historical size as a population we must also return to our historical selves and become more self-sufficient and consume A REASONABLE AMOUNT.

WANT TO LEARN MORE ABOUT SALMON? WATCH THIS GREAT DOCUMENTARY ON PBS!

http://www.pbs.org/wnet/nature/episodes/salmon-running-the-gauntlet/salmon-lifecycle/6559/

Images

http://articles-for-all.blogspot.com/
http://html.trrp.net/implementation/sediment_management.htm
http://seymoursalmon.com/images/lifecycle/alevin.jpg
http://www.yourfishingtipconnection.com/my_files/images/salmon_fry_2.jpg
http://www.planet-science.com/media/29341/atlantic%20salmon%20pre-smolt
http://swittersb.files.wordpress.com/2008/08/chinook_salmon.gif


Resources



1."Why Is Salmon Conservation Important?" Wild Salmon Center. Web. 06 Mar. 2012. <http://www.wildsalmoncenter.org/about/whySalmon.php>


2. "Salmonid Life Cycle." Center for Social and Environmental Stewardship. CFSES, 2005. Web. 3 Mar 2012. <http://www.cfses.org/elearning/tutorial.htm>.


3.United States. NOAA. Pacific Salmon & Steelhead: A Natural Wonder. C.A.: , 2010. Web. <http://swr.nmfs.noaa.gov/recovery/salm_steel.htm>.


4. "Salmon running the gauntlet: Salmon lifecycle." PBS. Thirteen- Educational Broadcasting Corporation, 2011. Web. 3 Mar 2012. <http://www.pbs.org/wnet/nature/episodes/salmon-running-the-gauntlet/video-full-episode/6620/>.