New methods developed to estimate Sea Lamprey Damage

[Spiel]

New methods developed to estimate Sea Lamprey Damage

Unique “signatures” in lamprey blood indicate specific fish which lampreys have preyed

 

February 11, 2008

Great Lakes Sport Fishing Council

 

 

ANN ARBOR, MI-A research team has developed new methods for estimating the diets of the lamprey, one of the most devastating species to have invaded the Great Lakes. Measuring the diets of lamprey will give scientists and managers a better picture of how much ecological and economic damage each sea lamprey causes over its life cycle.

 

While the findings support the long-held belief lamprey prefer to feed on large fish like lake trout, they also indicate that sea lamprey affect many other species, and that those effects differ from time to time and place to place.

 

In a study funded by the Great Lakes Fishery Commission, a group of federal, tribal and university researchers teamed with agencies, commercial fisheries and anglers to capture sea lamprey throughout Lake Superior, mainly from 2002 to 2004. The researchers examined the chemistry of lamprey tissues because certain types of carbon and nitrogen atoms, known as isotopes, yield clues about which fish species the sea lamprey feed upon.

 

"A fish like a lake trout from Lake Superior has a fairly predictable 'signature' of carbon and nitrogen isotopes in its blood," said Dr. Chris Harvey, a biologist with the National Oceanic and Atmospheric Administration and one of the study's lead researchers. "When a sea lamprey feeds on lake trout, we start to see the lake trout's isotopic signature appear in the lamprey tissues. If it feeds on other species as well, the lamprey's tissue chemistry looks more like a blend of signatures."

 

Sea lamprey invaded the upper Great Lakes after moving through the Welland Canal, probably in the early 20th Century. Reviled for their impacts on lake trout, salmon, and other fish populations, lamprey feed by rasping through the sides of fish and consuming blood and fluids. Although their numbers were reduced dramatically starting in the 1960s, lamprey continue to kill large numbers of lake trout and other valuable species.

 

The researchers found that lamprey throughout most of Lake Superior fed mainly on large, predatory fish during the study period. Between 60% and 90% of their diet was blood from predators like lake trout and possibly burbot. They also found that lamprey in western waters of the lake had more diverse diets than in eastern waters, with substantial feeding on whitefish and suckers. In Black Bay, a large bay in northwestern Lake Superior, over 50% of the lamprey diet was whitefish blood.

 

Preliminary results suggest lamprey impacts are felt by many species throughout the fish community besides lake trout. Some economically valuable species like herring and whitefish experience significant mortality, while some species that are less valuable, such as the deepwater siscowet, act as "buffer" species, absorbing sea lamprey impacts that might have otherwise affected fish with more commercial or recreational importance.

 

The research confirmed that lampreys prefer to feed on large fish like lake trout, though it also indicated lampreys affect many other species, and that those effects differ from time to time and place to place. "This refined view of who lamprey feed on at different times and in different areas is a big step," Harvey said. "Many of the pioneering impact models were forced to guess which species lamprey were killing. Our study removes some of that guesswork, and we hope it will lead to better accounting of the actual damage that sea lamprey do."