Great Lakes Fishery Commission

Sea lamprey (Petromyzon marinus) is native to rivers on the Atlantic coasts of North America and Europe but are invasive throughout the Great Lakes region. Extensive efforts are ongoing to develop selective passage techniques that will allow native sea lamprey to pass barriers in their native range but that will exclude sea lamprey in their invasive range. Because of the destructive potential of sea lamprey in the Great Lakes, the nature and scope of studies that can be performed within experimentally released invasive sea lamprey is limited. One solution is to conduct experiments with sea lamprey within the native range. Recent work on anadromous sea lamprey in their native range has confirmed that swimming ability could be an attribute by which to sort sea lamprey from other fishes. However, sea lamprey in the native range are larger than the invasive ones, and swimming performance is known to be allometric, which raises concerns about whether and to what extent information gleaned from native sea lamprey can be transferred to the Great Lakes system. Thus, there remains a need to assess the extent to which the native and invasive populations are similar, as well as to quantify any allometric differences in swimming performance. We addressed this need by studying the swimming performance of both native and GL populations using identical apparatus, with the aim of determining the extent of the difference in swimming performance of native and Great Lakes sea lamprey, and to assess whether these differences can be described by a single allometric relationship. \r\nWild anadromous and landlocked sea lamprey were collected in traps during their spring spawning migration in the Connecticut and Cheboygan watersheds, respectively. Fish were tagged with PIT-tags and subjected to swimming performance trials in a custom-made Blazka swim chamber designed to prevent attachment by lampreys. Fish were then measured, photographed, sampled for fat content using non-lethal methods, and euthanized. Following this, we removed the gonads and homogenized the specimens to perform measurements of energy proximate composition. Swimming performance data from both populations were analyzed using the critical swimming speed (Ucrit) methodology, and a time-to-event analytical framework to quantify the relationship between swim speed and time to fatigue (endurance), and how environmental and biological covariates may affect this relationship.\r\nThe two populations of sea lamprey differed in critical swimming speed and endurance. However, the direction and magnitude of effect differed between the two experimental methods: anadromous sea lamprey had a significantly higher Ucrit than landlocked sea lamprey but slightly lower endurance under faster flows. However, our findings suggest that once differences in body length are accounted for, there is relatively little difference in the prolonged and sprinting swimming ability between the two populations. The explanation for these conflicting findings is unknown but may be related to differing behavioral responses to the two methodologies. Further analyses are ongoing, including behavioral and kinematic analysis of trial recordings, and these may help to interpret the data. Besides, we found no evidence of any effect of environmental covariates, including water temperature and diel period (i.e., day or night) on swimming performance using either test methodology.\r\nThe results from this project improve knowledge on sea lamprey swimming ability over their geographic distribution range, which has implications for both conservation and control management programs. They also inform whether and to what extent results obtained with anadromous lamprey are transferable to Great Lakes river systems. \r\n\r\nRESEARCH HIGHLIGHTS:\r\n- The maximum aerobic swimming ability of sea lamprey was higher for the anadromous population than for landlocked population. Some landlocked sea lamprey, however, showed reduced motivation to swim against low velocities, which may explain some of the observed differences between the two populations.\r\n- Endurance swimming in fast flows is similar for anadromous and landlocked sea lamprey once body size is taken into consideration. Endurance is a function of flow velocity, fish body size, and maturation stage but was not affected by water temperature or time of day.\r\n- Anadromous and landlocked sea lamprey have a similar whole body fat content, which declines substantially and at a comparable rate during the spawning season.\r\n- The fat meter does not constitute a reliable non-lethal method to measure fat content in sea lamprey. While the instrument’s measurements captured relative trends in fat content across populations and sexes, as well as a decline over the spawning migration season, the measured values were only weakly correlated to those obtained by whole-body extractions.\r\nTaken together, these results have relevance for control (i.e. hydraulic barrier and trapping) and conservation (i.e. fishway design) of sea lamprey in their invasive and native ranges. Because our findings indicate that body length is the primary driver of differences in swimming ability between anadromous Connecticut River and landlocked Lake Huron sea lamprey, study results from one region can readily be applied to the other by converting flow values to body-lengths-per-second or a similar metric within the 0-2.25 BL/s range tested in this study.\r\n\r\nWhile the primary objectives have been achieved, work on this project is ongoing, with 1 peer reviewed paper in review, another near completion, and multiple presentations scheduled at regional and international conferences.\r\n

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