Identification of larval Pacific lampreys (Lampetra tridentata) , river lampreys (L. ayresi) , and western brook lampreys (L. richardsoni) and thermal requirements of early life history stages of lampreys. Annual report 2000

Bayer, J.M.; Meeuwig, M.H.; Seelye, J.G.

BPA Report DOE BP uary; 00000013-1: Unpaginated


Accession: 022798725

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Pacific lampreys (Lampetra tridentata) in the Columbia River Basin (CRB) are believed to have declined to only a remnant of their population prior to human development, and actions are currently being considered for their recovery (Close et al. 1995). Identifying biological factors that may limit lamprey production in the CRB is critical for their recovery, and while some biological information for this and sympatric species is available from studies in Canada (Pletcher 1963, Beamish 1980, Richards 1980, Beamish and Levings 1991), little is known about the biology of lampreys in the CRB. In order to identify biological factors that may limit lamprey production in the CRB it is important to be able to document the distribution and relative abundance of lampreys in streams and rivers tributary to the Columbia River. This may be accomplished through surveys of ammocoetes (larval lamprey), which can be readily collected from rearing habitat. However, characteristics currently employed to differentiate ammocoetes of different species may not be diagnostic (USGS, unpublished data). Therefore, developing ammocoete identification techniques is critical to determine the distribution and abundance of lampreys. Along with the ability to distinguish lamprey species in the field, understandingfactors influencing survival during early life history stages is important. One such factor is temperature, which may determine ammocoete abundance (Potter and Beamish 1975, Young et al. 1990, Youson et al. 1993). Understanding how temperature affects survival of early life history stages will help identify critical habitat needs that influence lamprey distribution and abundance (Piavis1961, Holmes and Lin 1994).The purpose of our research is to provide information necessary for population assessment and determination of critical habitat needs. Currently we have completed the first year of a multi-year study intended to: 1) determine diagnostic characteristics of egg and larval stages of Pacific, western brook, and river lampreys, and 2) examine the effects of temperature on the timing of developmental events and on survival of early life history stages of Pacific, western brook, and river lampreys. Both adult and ammocoete Pacific and western brook lampreys were collected from the field and transported to the Columbia River Research Laboratory (CRRL). We were unable to locate any river lamprey specimens within the CRB. Half of the ammocoetes were identified and sacrificed to provide genetic samples. We are currently awaiting finalization of genetic analyses, the results of which will give us a preliminary indication of our ability to accurately identify ammocoetes based on current diagnostic characteristic. The remaining ammocoetes were individually marked, held in aquaria, and sampled at six-week intervals. At each sampling event metamorphosis stage was noted and ammocoetes were identified to species, measured for length and mass, andphotographed. The purpose of this sampling is to test the validity of current diagnostic techniques by holding ammocoetes until metamorphosis, at which time positive identification can be made. To date we have sampled these ammocoetes seven times, and our species identification of individuals has been relatively consistent over time. Adult lampreys were spawned and the resulting progeny were reared for two purposes. First, eggs were incubated at four temperatures (10, 14, 18, and 22° C) and eggs and prolarval lampreys were measured (length and mass), photographed, and preserved at intervals over a period of 25 days. The samples collected will provide us with information about the timing of different developmental stages and the effects of temperature on the timing of developmental stages. The samples collected will also be used to determine morphological differences between Pacific and western brook lampreys and to develop an identification key for lamprey species of the CRB. Second, we used the progeny of laboratory-spawned lampreys to examine the effects of temperature on survival of early life stage Pacific and western brook lampreys. Both species of lamprey examined showed a marked decrease in survival at 22° C when compared to other temperatures (10, 14, and 18° C). Rate of development increased at warmer temperatures. Thus, it is important to consider the effects of temperature in the context of developmental stage. This project will be continued in 2001, and we will expand our efforts to locate river lampreys, which were not collected in 2000. We will continue tracking ammocoetes for validating species identification techniques and we will collect more samples for the purpose of developing a key for identifying lamprey species of the CRB. We will also continue to examine the effects of temperature on survival of early life stage lampreys and examine techniques for comparing temperature effects based on developmental stage.