Relationships between the Abundance of Pacific Lamprey in the Columbia River and Their Common Hosts in the Marine Environment

Abstract

The returns of Pacific Lamprey Entosphenus tridentatus to the Columbia River over the past decade have declined significantly compared with the peak returns of the 1950s and 1960s, with no quantifiable mechanisms identified. To determine if the abundance of documented host species in the marine environment is related to adult returns of Pacific Lamprey, we examined stock assessment data, commercial fishery statistics, and counts of adult fish at Bonneville Dam between 1997 and 2010. Significant positive correlations were observed between lamprey returns and abundance indices of Pacific Hake Merluccius productus, Walleye Pollock Theragra chalcogramma, Pacific Cod Gadus macrocephalus, Chinook Salmon Oncorhynchus tshawytscha, and Pacific Herring Clupea pallasii throughout the U.S. Pacific Northwest. Commercial landings of these species in Washington and Oregon were also significantly and strongly correlated to lamprey returns, with the exception of Walleye Pollock. Several of these fisheries have demonstrated significant reductions in mean landings since the 1950s and 1960s, and adult lamprey returns have declined proportionally. We further examined large‐scale and regional indices of oceanic productivity as a potential underlying mechanism. Multiple regression techniques indicated that host abundance was the principal factor in predicting lamprey returns, though inclusion of oceanic conditions increased the precision of the model. These results represent the first established relationship to recent trends of Pacific Lamprey returns to the Columbia River and indicate that spawning escapement is primarily a function of conditions experienced during the predatory phase of the life cycle. We hypothesize that Pacific Lamprey abundance in the Columbia River is cyclical in nature, but limited by availability of several host species over a potentially vast geographic range. Biologists and resource managers should reassess the relatively overlooked marine ecology of Pacific Lamprey.

Seasonal abundance, size, and host selection of western river (Lampetra ayresii) and Pacific (Entosphenus tridentatus) lampreys in the Columbia River estuary

“…We believe the majority of these wounds resulted from predation by western river lamprey, rather than by Pacific lamprey, because of 1) the seasonal overlap with western river lamprey and apparent absence of juvenile Pacific lamprey during summer, 2) wound locations on the dorsal surfaces of fishes (versus ventral surfaces for predation by Pacific lamprey; Beamish, 1980;Cochran, 1986;Clemens et al, 2010), and 3) wounds that were elongated rather than circular and did not completely penetrate the muscle layer ( Fig. 3; Beamish, 1980;Beamish and Neville, 1995;Murauskas et al, 2013). We observed no wounds that we were confident were due to Pacific lamprey.…”

“…Lack of lamprey wounds on larger American shad or extremely abundant northern anchovy (Engraulis mordax) may also reflect limited opportunity: large shad may have just re-entered freshwater and were moving rapidly upstream (Hammann, 1981), and northern anchovy are a marine species that typically enter the estuary only during high tides (Weitkamp et al, 2012). Murauskas et al (2013) argued that the abundance of adult Pacific lamprey in the Columbia River is at least partially controlled by the abundance of their hosts during their parasitic phase in marine environments. If this idea applies equally to western river lamprey in the Columbia River estuary, we expect that their population should be relatively healthy because of the abundance of potential prey in the estuary.…”

“…Although there is considerable effort underway to understand the habitat requirements of lampreys in freshwater (e.g., Streif, 2009;Jackson and Moser, 2012), very little is known about estuarine and marine ecology for most lamprey populations (Mesa and Copeland, 2009;Murauskas et al, 2013;Siwicke, 2014), including those in the Columbia River. Information on estuarine ecology is necessary to understand this fundamental stage of the life cycle and is essential to document the timing of transitions between freshwater and marine habitats.…”

The haematophagous feeding stage of anadromous populations of sea lamprey Petromyzon marinus: low host selectivity and wide range of habitats

“…As a result of overfishing and other factors, populations of targeted fishes have been declining over decades (Pauly et al, 1998;Jackson et al, 2001). Although the role of targeted species in the diet of P. marinus may be overestimated because fisheries are often the source of information, this decline may directly affect populations of anadromous sea lamprey as host abundance can be the principal factor in predicting adult lamprey returns to the rivers (Murauskas et al, 2013). This paper also records haematophagous feeding of P. marinus in freshwater in Ireland and in French Britanny (Table 1).…”

“…Therefore, as also suggested by Lança et al (2013) marine distribution of P. marinus seems to occur mainly in the continental shelf and slope regions until the mesopelagic level, with a small part of the population reaching more remote areas. Distribution of anadromous lampreys at sea seems to be linked to the abundance of hosts and their mobility (Johnson & Anderson, 1980;Orlov et al, 2008;Lança et al, 2013;Murauskas et al, 2013). Individuals attached to large hosts with wide dispersion patterns could get constant and highly nutritive food but that strategy could also increase the risk of not returning to fresh waters to reproduce (Lança et al, 2013).…”