U.C Davis Predation Science Panel's final report.


[Bulletin Board]


Posted by Mike McKenzie on 2013-10-03 20:30:36

Some may remember the report I published back on July 26th about the predation workshop at UC Davis. Striperfest paid for representation and monitoring for that workshop.

The expert panelists have delivered their final report and here I quote their Executive summary....

"We examined a set of 24 papers and observed presentations by researchers to assess the status of information and potentially establish conclusions regarding the importance of fish predation on salmonid populations in the Delta. Available data and analyses have generated valuable information regarding aspects of the predation process in the Delta but do not provide unambiguous and comprehensive estimates of fish predation rates on juvenile salmon or steelhead nor on population-level effects for these species in the Delta. Recent survival studies are based on acoustic tagging of larger hatchery-raised fish from ~95 to >250 mm FL. Although it is assumed that much of the short-term (<30 d) mortality experienced by these fish is likely due to predation, there are few data establishing this relationship. Juvenile salmon are clearly consumed by fish predators and several studies indicate that the population of predators is large enough to effectively consume all juvenile salmon production. However, given extensive flow modification, altered habitat conditions, native and non-native fish and avian predators, temperature and dissolved oxygen limitations, and overall reduction in historical salmon population size, it is not clear what proportion of juvenile mortality can be directly attributed to fish predation. Fish predation may serve as the proximate mechanism of mortality in a large proportion of the population but the ultimate causes of mortality and declines in productivity are less clear. For example, stress caused by harsh environmental conditions or toxicants will render fish more susceptible to all sources of mortality including predation, disease or physiological stress. We also recommend a variety of structural changes to the manner in which research is performed in the Delta. These include creation of a system-wide GIS including layers for available physical, chemical and biological data including hatchery releases. Next, we recommend that methods be standardized for important research topics such as fish abundance estimates, tagging studies, dietary studies, etc. This process has recently been conducted by the National Ecological Observatory Network and their work could serve as a starting point for a similar process in the Delta. Our research indicated that it was difficult to locate information for many topics and we recommend creation of a searchable data repository for research conducted in the Delta, similar to that used by NSF Long-Term Ecological Research sites. Finally, we suggest a series of research topics that must be addressed to reach scientifically valid conclusions regarding the role of fish predation on salmonid populations in the Delta and provide examples of potential study designs from the literature."

Those that want, can read the full report here:

https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=73874

I haven't had time to read the report yet (I'm getting ready to leave for the East Coast) but just reading the Executive Summary, it's interesting to see the amount of agreement between what the expert panel says and what Striperfest put forth in our arguments against predation studies being used in the CSD (Coalition for A Sustainable Delta Har, Har!)Lawsuit against DFG with respect to the striped bass fishing regulations. As everyone knows they lost the suit and now they really know why! They did not have the science to support their assumptions. The Judge told them that then and now, the expert scientists have told them!

Be proud Striperfest supporters!!!

Mike


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