Robert L. McLaughlin

Low-Head Barrier Dams Restrict the Movements of Fishes in Two Lake Ontario Streams

Abstract The Great Lakes Fishery Commission (GLFC) is considering greater use of low-head barrier dams on stream tributaries of the Laurentian Great Lakes to control populations of sea lampreys Petromyzon marinus. The impact of these barriers on nontarget fishes is not known. A mark–recapture study on four Lake Ontario streams examined movements of fishes in streams with (barrier) and without (reference) low-head barriers. A significantly lower proportion of fishes moved across a real barrier on barrier streams than across a hypothetical barrier on reference streams (0.15 versus 0.50, respectively). The impact of the barriers on movement was more pronounced in spring and fall than in summer. However, the likelihood of fishes moving versus not moving between sample segments on either side of a barrier location (but not across the barrier) did not differ significantly between barrier and reference streams. The upstream (longitudinal) decline in species richness was greater for barrier streams than for refer...

Adaptive peaks and alternative foraging tactics in brook charr: evidence of short-term divergent selection for sitting-and-waiting and actively searching

Abstract Some recently emerged brook charr (Salvelinus fontinalis) inhabiting still-water pools along the sides of streams are sedentary and eat crustaceans from the lower portion of the water column. Others are more active and eat insects from the upper portion of the water column. We provide evidence that this divergent foraging behavior reflects short-term divergent selection brought about by intraspecific competition in the presence of alternative food sources. Rates of encounters and interactions between individuals were density dependent, and encounter and interaction events were closely timed with prey capture attempts. In addition, aggressive fish made more foraging attempts per minute than nonaggressive fish. Aggressive fish were also either inactive or very active, while nonaggressive fish exhibited intermediate levels of activity. Growth rate potential, an important component of fitness during the early life stages of brook charr, was assessed using tissue concentrations of RNA and found to be highest for sedentary fish and for active fish making frequent foraging attempts, and lower for fish exhibiting intermediate levels of activity. Our findings support contentions that individual behavior plays an important role during initial steps in the evolution of resource polymorphisms.

Research to Guide Use of Barriers, Traps, and Fishways to Control Sea Lamprey

ABSTRACT This paper provides a rigorous and directed research framework for fostering innovations in the design, implementation, and operation of barriers, traps, and fishways used to control the sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes. It was developed to support the Great Lakes Fishery Commissions milestone pledging to decrease reliance on chemical lampricides and achieve 50% of sea lamprey suppression through alternative control technologies, including barriers and traps. The paper first substantiates the need to develop a long-term research plan for barriers, traps, and fishways by summarizing (i) current management challenges, (ii) the barrier, trap, and fishway options being used to meet these challenges, and (iii) the key uncertainties in our knowledge regarding these options. The paper then proposes a long-term research strategy that envisions a transition from barriers designed to block the upstream spawning migrations of sea lamprey, to barrier and trap combinations that facilitate physical removal of sea lamprey and, in some cases, passage of non-target fishes, to barrier and trap designs that are specific to sea lamprey, transparent to non-target fishes, and safer for operators. Thirteen research needs are identified to support this strategy along with a general work plan on how they can be achieved. The research needs and work plan highlight the exceptional opportunity to develop the Great Lakes basin as a leading, international research center for fish migration and passage, and the development of environmentally friendly barriers.

Low-head Sea Lamprey Barrier Effects on Stream Habitat and Fish Communities in the Great Lakes Basin

Abstract Low-head barriers are used to block adult sea lamprey ( Petromyzon marinus ) from upstream spawning habitat. However, these barriers may impact stream fish communities through restriction of fish movement and habitat alteration. During the summer of 1996, the fish community and habitat conditions in twenty-four stream pairs were sampled across the Great Lakes basin. Seven of these stream pairs were re-sampled in 1997. Each pair consisted of a barrier stream with a low-head barrier and a reference stream without a low-head barrier. On average, barrier streams were significantly deeper (df = 179, P = 0.0018) and wider (df = 179, P = 0.0236) than reference streams, but temperature and substrate were similar (df = 183, P = 0.9027; df = 179, P = 0.999). Barrier streams contained approximately four more fish species on average than reference streams. However, streams with lowhead barriers showed a greater upstream decline in species richness compared to reference streams with a net loss of 2.4 species. Barrier streams also showed a peak in richness directly downstream of the barriers, indicating that these barriers block fish movement upstream. Using Sorensons similarity index (based on presence/absence), a comparison of fish community assemblages above and below low-head barriers was not significantly different than upstream and downstream sites on reference streams (n = 96, P > 0.05), implying they have relatively little effect on overall fish assemblage composition. Differences in the frequency of occurrence and abundance between barrier and reference streams was apparent for some species, suggesting their sensitivity to barriers.

Balancing Aquatic Habitat Fragmentation and Control of Invasive Species: Enhancing Selective Fish Passage at Sea Lamprey Control Barriers

Abstract Barriers to prevent spawning migrations of sea lampreys Petromyzon marinus remain an important component of an integrated sea lamprey management program in the Laurentian Great Lakes. Concerns about effects on nontarget fishes have led to the construction of specially designed vertical-slot trap-and-sort fishways to mitigate potential barrier effects. To improve passage at these fishways, we used passive integrated transponder technology to assess the performance of two fishways located on low-head sea lamprey barriers. Fishways on the Big Carp River (which flows into Lake Superior) and Cobourg Brook (which flows into Lake Ontario) were assessed for attraction efficiency, trap attraction and retention, and passage efficiency. Based on the results of these assessments, fishways were modified by increasing the trap volume and altering the funnel characteristics to reduce escapement from the trap and then reassessed. Attraction efficiency for all tagged fish was high (≥80%) at both sites in all year...

Relative Importance of Water Temperature, Water Level, and Lunar Cycle to Migratory Activity in Spawning-Phase Sea Lampreys in Lake Ontario

Abstract We analyzed historical trapping records from six Lake Ontario tributaries to (1) compare the relative importance of water temperature, water level, and lunar cycle to migratory activity in upstream-migrating sea lampreys Petromyzon marinus and (2) determine whether the relative importance of these variables differs among streams. We found significant stream-dependent differences in the relative importance of the environmental variables. Water temperature was the best predictor of migratory activity in all six streams. The seasonal distribution of migratory activity was related to mean stream temperature, with an estimated peak migration temperature of approximately 15°C. Changes in stream temperature were equally as important. Migratory activity was stimulated when mean stream temperature increased between consecutive days and was suppressed when mean stream temperature decreased between consecutive days. Water level was a reliable predictor of migratory activity only in the two smallest streams....

UNDERSTANDING UNCERTAINTY IN THE EFFECT OF LOW-HEAD DAMS ON FISHES OF GREAT LAKES TRIBUTARIES

Small dams represent one of the most widespread human influences on riverscapes. Greater understanding of how these structures affect aquatic organisms is needed to ensure that decisions regarding their construction and removal strike an appropriate balance between components of human and ecosystem services. Within the basin of the Laurentian Great Lakes, the effects that in-stream barriers (dams) used to control the non-native, parasitic sea lamprey (Petromyzon marinus) on the diversity of non-target fishes is a significant concern for fishery managers. A previous study indicated that upstream changes in the species richness of non-target fishes observed in 24 streams with a sea lamprey barrier relative to paired reference streams (a measure of effect size) was variable across the basin. We examined the degree to which the variance in effect size could be attributed to imprecision in the field sampling protocol used to estimate effect sizes, differences in catchment-scale landscape attributes between barrier and reference streams within pairs, and differences in landscape attributes at different spatial scales among barrier streams. Simulation modeling and analyses of repeated field measurements made for a subset of streams demonstrated that a large variance in effect size is expected for the field sampling design and that estimates of effect size measured for individual barrier streams are imprecise. Regression models and multimodel inference methods based on Akaikes Information Criterion provided less support for hypotheses linking effect size to landscape attributes. Mean effect size, adjusted for the influences of landscape characteristics within and across stream pairs, provides the most reliable and least biased estimate of the effect of sea lamprey barriers on the richness of nontarget fish species. With the information currently available, landscape characteristics of catchments cannot be used to help decision makers anticipate effects sizes for candidate streams being considered for future barrier construction. Our findings will help fishery managers in the Laurentian Great Lakes make more informed decisions regarding the use and placement of sea lamprey barriers and achieve their objective of delivering an integrated pest management plan for sea lamprey control that is environmentally and economically sound and socially acceptable.

Foraging behaviour and brain morphology in recently emerged brook charr, Salvelinus fontinalis

Recently emerged brook charr (Salvelinus fontinalis) foraging in still-water pools along the sides of streams are either active, feeding on insects from the upper portion of the water column away from the stream bank, or sedentary, feeding on crustaceans emerging from the hyporheic zone near the stream bank. We tested whether the frequency of movement displayed by individual brook charr searching for prey in the field was related to the relative volume of the telencephalon, a brain region involved with movement and space use in fishes. Movement of individuals searching for prey was quantified in the field, individuals were captured and volumes of the telencephalon and of the olfactory bulbs, a brain region neighbouring the telencephalon but not implicated in space use, were measured. Individuals with larger telencephalon volumes moved more frequently on average while searching for prey in the field than did individuals with smaller telencephalon volumes. The frequency of movement was unrelated to differences in the volume of the olfactory bulbs, suggesting that the relationship between telencephalon volume and movement was not a consequence of differences in overall brain size. Demonstrating a correlation between foraging behaviour and brain morphology for brook charr exhibiting different foraging tactics suggests that diversification in brain structure and function could be important aspects of the foraging specialization believed to occur during early stages in the evolution and development of resource polymorphisms.

Achieving the Benefits of Sea Lamprey Control While Minimizing Effects on Nontarget Species: Conceptual Synthesis and Proposed Policy

Managers of the fishery within the Laurentian Great Lakes basin consistently strive to minimize potential nontarget environmental effects of methods used to control nonnative sea lampreys (Petromyzon marinus). This paper develops a framework for achieving the benefits of sea lamprey control while minimizing effects on nontarget species. It is a synthesis of discussions held by a working group assigned this task during the Sea Lamprey International Symposium II. The first part of the paper examines conceptually how inclusion of effects on nontarget species in the decision-support system used by the Great Lakes Fishery Commission (GLFC) can affect overall control costs and treatment success. The second part summarizes reasons why the identification and interpretation of nontarget effects are challenging and complicated. The last part proposes an initial, lake-wide policy framework the GLFC and its agents could use to guide the accommodations made to reduce nontarget effects. The framework seeks to achieve the lake-wide benefits of sea lamprey control while accommodating lake-wide and regional effects on species other than the sea lamprey.

Tissue concentrations of RNA and protein for juvenile brook trout (Salvelinus fontinalis): lagged responses to fluctuations in food availability.

To be useful as short-term indices of nutritional status when food availability varies, wet weight-at-length and tissue concentrations of nucleic acids and protein must covary closely with a fishs recent feeding history. We measured changes in these indices for young brook trout (Salvelinus fontinalis) (fork length: 20–34 mm) reared under alternating, 4 to 5 d periods of food provisioning and food deprivation. Weight-at-length corresponded closely with current feeding conditions, being higher when the trout were fed than when they were deprived. Concentrations of RNA and protein, however, did not correspond closely with current feeding conditions. Instead, there were significant carry-over effects whereby responses to feeding conditions experienced in one treatment period were not exhibited until the following treatment period. Food provisioning had positive carry-over effects on concentrations of RNA and protein while food deprivation had negative carry-over effects. Consequently, food-deprived trout sometimes had higher concentrations of RNA and protein than well fed trout. Since wild fish may experience short-term fluctuations in food availability, lagged responses in concentrations of nucleic acids or protein like those reported here could hamper attempts to use these biochemical measures to assess the nutritional status of juvenile fish in the field.