Sunday, June 27, 2010

Diversity: A key factor in species survival

by Lawrence G. Dominguez - June 27th, 2010

Fish biologist Lawrence Dominguez highlights a crucial concept for salmon and the implications here are clear: the habitat of the Snake River basin remains a critical piece of the ongoing work to ensure the return to abundance of endangered salmon in the Northwest.

Growing up, I instinctively knew that diversity was a good thing. I didn't know what it meant but when my mom used to tell me not to put all my eggs in one basket I felt that she meant well, even though growing up in the suburbs didn't require a trip to the coop every morning. From Hot Wheels to baseball card collections, the king of the block was the one who had the greatest assortment. It wasn't until late in high school and in college biology and ecology classes that I began to see those same fundamental truths apply to the survival and population growth of animals.

Diversity of populations plays out in various ways in the animal kingdom, starting with how many eggs or offspring that can be produced. This measure of fecundity varies vastly among species; oysters produce 55-114 million eggs, some halibut up to a million eggs per day (!), a spawning salmon lays hundreds to thousands in her redd (nest), birds have between one and 20 offspring, mammals generally up to ten. In general, fecundity is inversely proportional to the amount of parental investment. Salmon parents do a great job of making and protecting nests, but are not around to protect them from predators in the early days and weeks. They embody the very definition of posthumous nurturing, however. (1)

Imagine how much diversity of the Pacific salmon is represented by the combined millions and millions of salmon eggs, growing and hatching in the thousands of Pacific Northwest streams and lakes every year. Successful diversity continues after that with their ability to access diverse and productive habitats (lakes or streams, rivers, estuaries, oceans) throughout their various life stages, and concludes with their ability to make it back to their river of origin to give them the opportunity to pass on that diversity to future generations.

Maintaining biological diversity (habitats, species, and population diversity) has been a cornerstone for providing what species need. It is at the forefront of topics regarding species conservation now more than ever – and rightly so, amidst diminishing animal populations around the world. A recent article in Nature magazine (2) highlights the significance of population and life history diversity in how a population performs.

Using an illustration to which we can all relate to these days, the authors describe the success of a diverse financial portfolio in stressful, uncertain financial times, to illustrate that a diversified "population portfolio" can similarly still perform in challenging circumstances. However, populations inhabiting landscapes that have been heavily altered or influenced – whether by extensive land use alterations, habitat loss, climate change, hatchery impacts, or hydropower influences – will have very difficult times persisting. Adapting to these influences was not necessarily a consideration when the "resiliency portfolio" for salmon populations was "assembled."

Certainly some of those resiliency allocations are becoming manifest in the changing environment but there is uncertainty about how much of that can be explained in adapting to changing environments or simply pushing the salmon to less-preferred areas of their tolerances. Several years ago similar considerations of population diversity were made in an analysis of multiple populations (3) to suggest characteristics of populations that warrant the highest conservation priorities. These are populations that have a high potential for adaptive variation (use of various habitats, different timing, life history diversity), a genetic structure with propensity to spread to larger areas, a sharing of habitats with other populations, and a sharing of distinctive habitat characteristics among populations.

The authors noted that watersheds without restrictive land use areas (that would otherwise provide productive areas to allow portions of the population to recover), should be the highest conservation priorities. Both these articles concur, on different scales, of the importance of population diversity to restore or maintain viable salmon populations or fisheries. A greater source of diverse populations, aided by effective connections between them and their habitats, provide a greater number of pathways to recovery.

Many of the baseball cards I collected in my childhood ended up being clothes-pinned to my bike spokes to simulate a motorcycle sound. Decades later, I humbly learned that the combined value of some of those cards would have likely sent me on a different life history path than a salmon biologist. In the same vein, while we may not have understood it in the past, the value of our remaining diversity of salmon habitats and populations is increasing as its abundance diminishes and threats increase. We must ensure access to and connectivity of habitats, and enough adult returns to the streams to satisfy the fundamental need of diversity in recovery efforts.

Finally – and vitally – let us not overlook the values we have yet to understand, as the recent Nature article demonstrates. The closer we look at, and the more we learn about, salmon populations and their needs, the more factors we must consider in maintaining and recovering fisheries.

by Lawrence G. Dominguez, Fish Ecologist
Cramer Fish Sciences
Providing innovative solutions for fisheries and environmental challenges, serving Oregon, California, Washington, Idaho, Montana and Alaska.

Mr. Dominguez is a salmon ecologist with expertise in habitat restoration ecology and Endangered Species Act compliance and recovery. He can be reached at This e-mail address is being protected from spambots. You need JavaScript enabled to view it or by phone at 360-915-4194.

(1) While alive, adult salmon provide protection for their young for only several days after spawning,, however, through the form of providing nutrient and tissue, they contribute fundamental elements of the food web to the watershed where their young will emerge from the gravel and feed.

(2) Schindler, D.E., R. Hilborn, B. Chasco, C.P. Boatright, T.P. Quinn, L.A. Rogers, and M.S Webster. 2010. Population diversity and the portfolio effect in an exploited species.

(3) Halupka, K.C., M.F. Willson, M.D. Bryant, F. H. Everest, and A.J. Gharett. 2003. Conservation of population diversity of Pacific salmon in Southeast Alaska. North American Journal of Fisheries Management (23): 1057-1086.

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