2022

Permanent URI for this collectionhttps://hdl.handle.net/1807/109474

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Optimal dynamic spatial closures can improve fishery yield and reduce fishing-induced habitat damage
(Canadian Science Publishing, 2022-12-22) Poulton, Anna Jennifer; Sethi, Suresh A.; Ellner, Stephen P; Smeltz, Timothy Scott
Bottom-towed fishing gears produce significant amounts of seafood globally but can result in seafloor habitat damage. Spatial closures provide an important option for mitigating benthic impacts, but their performance as a fisheries management policy depends on numerous factors, including how fish respond to habitat quality changes. Spatial fisheries management has largely focused on marine protected areas with static locations, overlooking dynamic spatial closures that change through time. To investigate the performance of dynamic closures, we develop a spatial fishery model with fishing-induced habitat damage, where habitat quality can affect both fish productivity and movement. We find that dynamic spatial closures often achieve greater harvest and habitat protection than fixed marine protected areas or conventional non-spatial maximum sustainable yield management, especially under strong habitat-stock interactions. Determining optimal dynamic spatial closures may require considerable information, but we find that simple policies of fixed-schedule rotating closures also perform well. Dynamic spatial closures have received less attention as fisheries management tools, and our results demonstrate their potential value for addressing both harvest and habitat impacts from fishing.
Impeding access to tributary spawning habitat and releasing experimental fall-timed floods increases brown trout immigration into a dam's tailwater
(Canadian Science Publishing, 2022-11-10) Healy, Brian Daniel; Yackulic, Charles B.; Schelly, Robert C.
River ecosystems have been altered by flow regulation and species introductions. Regulated flow regimes often include releases designed to benefit certain species or restore ecosystem processes, and invasive species suppression programs may include efforts to restrict access to spawning habitat. The impacts of these management interventions are often uncertain. Here, we assess hypotheses regarding introduced brown trout (Salmo trutta) movement in a regulated river. We model mark-recapture data in a multistate framework to assess whether movement was affected by the operation of a tributary weir (restricting access to spawning habitat), experimental releases of fall-timed High Flow Experiments (Fall HFEs), or simply increased during the fall, spawning season. Our results suggest that the presence of the weir led to reduced tributary homing and the release of Fall HFEs stimulated upstream movement and straying. Both effects are of a similar magnitude, however the fall HFE effect is more certain. Our results suggest the expansion of an invasive species was stimulated by management interventions, and demonstrate the potential for unanticipated outcomes of restoration in highly altered river ecosystems.
Hierarchical genetic structure in a direct-developing whelk (Buccinum undatum) throughout the western North Atlantic
(Canadian Science Publishing, 2022-09-26) Sturch, William H; D'Aloia, Cassidy
Direct-developing marine species lack a pelagic larval phase and are therefore predicted to have limited dispersal capacity and exhibit strong genetic structure over small spatial scales. Nevertheless, empirical work suggests that developmental mode, alone, cannot always explain realized connectivity patterns. We characterized spatial genetic structure within the western North Atlantic lineage of the waved whelk (Buccinum undatum), a direct-developing gastropod that is the target of an emerging fishery. We genotyped individuals throughout Atlantic Canada using 1,052 single nucleotide polymorphisms (SNPs), documenting strong hierarchical genetic structuring throughout this region. Overall, pairwise genetic structure estimates were high, with two major genetic clusters separating southwestern and northeastern sites. But more complex patterns emerged at smaller spatial scales. Notably, pairs of sites on deeper offshore habitat exhibited panmixia, despite being separated by up to 100 km, whereas inshore and intertidal populations spaced at comparable distances were strongly genetically divergent. Collectively, our multi-scale analyses revealed that direct developers can exhibit genetic patterns that do not conform to simple geographic expectations. Future exploration of potential depth-variable connectivity is warranted, especially among harvested populations.
Drivers of Atlantic herring decline and evidence basis for fisheries closures and rebuilding plans
(Canadian Science Publishing, 2022-11-22) Calder, Ryan; McDermid, Jenni L.; Boudreau, Stephanie A.
Atlantic herring (Clupea harengus) are economically and ecologically significant but have been in decline in Atlantic Canada due to an uncertain combination of environmental recruitment controls, predation, and fishing (commercial fishery and poorly documented bait removals). Fisheries and Oceans Canada partially closed Atlantic mackerel (Scomber scombrus) and herring fisheries in March 2022 amid controversy and disagreement. Here, we develop a conceptual model for natural and anthropogenic controls on herring abundance centered on the southern Gulf of St. Lawrence (sGSL) and evaluate the likely importance of each. We provide the first estimates of the magnitude of bait fishery withdrawals in the sGSL. The decline in sGSL herring is likely driven by natural predation exacerbated by fishing. Bait fishery removals were 182 tonnes in 2021, suggesting that previous estimates for removals of spring-spawning herring were ~30% too low. Fisheries closure is consistent with a precautionary approach given uncertainties and irreversibility of stock collapse. Ecosystemic models are needed but will be difficult to develop given the incomplete understanding of prey substitutability and net effect of interacting environmental processes.
Comparing the performance of three common species distribution modelling frameworks for freshwater environments through application to eel species in New Zealand
(Canadian Science Publishing, 2022-11-14) Charsley, Anthony Rafael; Sibanda, Nokuthaba; Hoyle, Simon; Crow, Shannan
Globally, many freshwater species are depleting and require population-level assessments. Many species distribution modelling frameworks are available for such assessments, but comparisons are needed to understand their predictive performance under different settings. K-fold cross-validation techniques were employed to compare the performance of three commonly used frameworks: machine learning, spatio-temporal modelling, and Gaussian process modelling. Through application to New Zealand populations of Longfin Eel (Anguilla dieffenbachii) and Shortfin Eel (Anguilla australis), area under the receiver operating characteristic curve (AUC) and true skill statistic (TSS) model performance metrics were estimated. All modelling frameworks produced approximately consistent distribution maps but differed in predictive performance. AUC and TSS results indicated that model predictions from the spatio-temporal modelling framework were the most accurate, followed by Gaussian process modelling. However, all modelling frameworks performed similarly when training and test data were spatially independent. In addition to having the best predictive performance, the spatio-temporal modelling framework showed the greatest promise for advancement in population-level assessment and is therefore recommended. The results are useful for freshwater ecologists and resource managers to make informed decisions on the appropriateness of a modelling framework for their research objective.
The influence of stream tributaries to lakes and upstream forest harvest on benthic, lake delta communities
(Canadian Science Publishing, 2022-11-07) Becu, Mariella H. J.; Michalski, Tracy A.; Richardson, John S
Lake deltas (LDs) receive nutrient and energy subsidies from upstream habitats. These inputs can support LD benthic production. However, LDs may also receive impacts from upstream disturbance. Small lakes in coastal British Columbia often have inflow streams from areas with forest harvesting, which is pervasive in this region. Forest harvesting impacts can alter stream production, although downstream impacts on lakes, compared to streams, are less studied and understood. We aimed to test whether benthic LD communities (biofilm and invertebrates) are more productive and/or diverse compared to other communities along the lakeshore (LS) (non-LDs), and whether there are differences in LD communities associated with upstream harvesting. We compared LD communities with upstream riparian areas that were harvested (HLD) or relatively undisturbed (ULD), and LS sites. We found that while community structure was similar across sites, ULDs had higher biofilm and invertebrate standing stocks (1.5- and 2-times higher, respectively) than HLDs and LS sites. Our results suggest subsidies and benthic production were higher at ULDs. These results advance our understanding of forest harvesting disturbance and stream-lake connectivity.
Emerald ash borer invasion of riparian forests alters organic matter and bacterial subsidies to south Michigan headwater streams
(Canadian Science Publishing, 2022-09-27) Larson, Courtney Elizabeth; Engelken, Patrick; McCullough, Deborah G.; Benbow, Mark Eric
Emerald ash borer (EAB), has killed millions of ash trees in the United States and Canada, yet impacts on terrestrial-aquatic linkages are largely unknown. Ash tree death along streams creates canopy gaps, increasing light to riparian plants and potentially affecting organic matter subsidies. Six EAB-related canopy gaps along streams across a gradient of timing of EAB invasion in Michigan were characterized for characterized coarse woody debris (CWM), terrestrial and aquatic leaf litter and their associated bacterial communities, and macroinvertebrates upstream, downstream, and at the center of the gap. Stream sites downstream of EAB-related canopy gaps had significantly lower dissolved oxygen and macroinvertebrate diversity than sites upstream and at the gaps. Yet there was no difference in CWM or aquatic leaf litter, likely due to downstream movement of organic matter from upstream riparian sources. Low abundance bacterial amplicon sequence variants unique to gap or forest were detected in leaves and leaf litter, suggesting EAB-related canopy gaps altered leaf associated bacterial communities. Overall, EAB invasion indirectly impacted some variables, while organic matter dynamics were resistant to change.
Modeling coho salmon (Oncorhynchus kisutch) population response to streamflow and water temperature extremes
(Canadian Science Publishing, 2022-09-09) Bellmore, J. Ryan; Sergeant, Christopher J; Bellmore, Rebecca A.; Falke, Jeff A.; Fellman, Jason B.
Models that assess the vulnerability of freshwater species to shifting environmental conditions do not always account for short-duration extremes, which are increasingly common. Life cycle models for Pacific salmon (Oncorhynchus spp.) generally focus on average conditions that fish experience during each life stage, yet many floods, low flows, and elevated water temperatures only last days to weeks. We developed a process-based life cycle model that links coho salmon (O. kisutch) abundance to daily streamflow and thermal regimes to assess: 1) How does salmon abundance respond to short-duration floods, low flows, and high temperatures in glacier-, snow-, and rain-fed streams? 2) How does the temporal resolution of flow and temperature data influence these responses? Our simulations indicate that short-duration extremes can reduce salmon abundance in some contexts. However, after daily flow and temperature data were aggregated into weekly and monthly averages, the impact of extreme events on populations declined. Our analysis demonstrates that novel modeling frameworks that capture daily variability in flow and temperature are needed to examine impacts of extreme events on Pacific salmon.
Bet-hedging bigmouth buffalo (Ictiobus cyprinellus) recruit episodically over a 127-year timeframe in Saskatchewan
(Canadian Science Publishing, 2022-10-14) Lackmann, Alec R.; Sereda, Jeff; Pollock, Mike; Bryshun, Reid; Chupik, Michelle; McCallum, Katlin; Villeneuve, James; Bielak-Lackmann, Ewelina S.; Clark, Mark E.
The bigmouth buffalo (Ictiobus cyprinellus) is an iconic freshwater fish native to North America that is in decline. Recent studies have revealed bigmouth buffalo exhibit a slow pace of life, yet demographic information on bigmouth buffalo outside of North Dakota and Minnesota is lacking. We used otoliths to investigate population demographics of bigmouth buffalo in Canada, and also monitored bigmouth buffalo spawning frequency and reproductive success in the wild. From a sample of 52 fish collected during 2018 – 2021 we found bigmouth buffalo from the Qu’Appelle system more than 125 years old. Only 13 year classes ranging from 1894 – 1997 were evident with only one year class since 1948, indicating recruitment has been episodic. During the past decade (2013 – 2022) bigmouth buffalo have spawned only once (May of 2013) in Buffalo Pound Lake. This spawning effort culminated in recruitment failure because the water-level recession rate was too rapid. Our findings indicate that bigmouth buffalo spawning attempts as well as recruitment occur within a narrow range of water-level fluctuations that may rarely occur, which is enabled by their supercentenarian lifespan, and has direct implications for the conservation of this species.
Territories within groups: the dynamic competition of drift-feeding juvenile Chinook Salmon in 3-dimensional space
(Canadian Science Publishing, 2022-08-09) Neuswanger, Jason R; Rosenberger, Amanda E; Wipfli, Mark S; Hughes, Nicholas F
Salmonid populations are often regulated by territorial competition among juveniles for food and space. In the canonical view, salmonid territories are spaced horizontally across the river bottom in a 2-D mosaic. However, some juveniles instead feed in tight, three-dimensional (3-D) social groups. To investigate whether territoriality is possible within such groups, we applied a new concept—the momentary home range—to quantify the size, exclusivity, and temporal dynamics of 3-D space use by juvenile Chinook Salmon (Oncorhynchus tshawytscha) in the Chena River, Alaska. Individual strategies spanned a broad continuum of exclusivity and stationarity. However, some of the largest, most dominant fish in each group aggressively defended stationary, exclusive feeding spaces and thus were unambiguously territorial. Transient floaters entered and left the group quickly. A majority of fish were not aggressive but nevertheless occupied exclusive, stationary spaces that probably function as territories with regard to resource distribution and population regulation. The presence of territoriality within social groups, in a 3-D configuration, expands the known domain of this important behavior.
Atlantic salmon of wild and hatchery origin have different migration patterns
(Canadian Science Publishing, 2022-11-14) Iden Nilsen, Cecilie; Vollset, Knut Wiik; Velle, Gaute; Barlaup, Bjørn T.; Normann, Eirik Straume; Stöger, Elisabeth; Lennox, Robert J.
Hatcheries are frequently used to support or restore threatened Atlantic salmon populations. However, little is known about how rearing affects behaviour and fitness of hatchery adults that return to the river to spawn. We used acoustic telemetry to compare migration patterns exhibited by hatchery- (N=16) and wild (N=12) Atlantic salmon spawners within a river system in Norway. Hatchery Atlantic salmon in this study were released as smolts and were identified by their missing adipose fin upon return to rivers after 1+ winters spent at sea. Hatchery origin Atlantic salmon displayed aberrant reverse movement behaviour, by moving with frequent reversals between the river and the fjord, a behaviour that was not observed in any wild Atlantic salmon. No difference in survival and outmigration timing after spawning was found for the two groups. The observed effect of hatchery origin on behavior may have implications for stock assessments made to assess the progress of restoration in the river, particularly if behavioural differences impact catchability or detections of returning adult salmon. The consequences of different movement patterns are uncertain, however, movements are energetically costly and may ultimately impact the fitness of hatchery Atlantic salmon.
Interactions between life history and the environment on changing growth rates of Chinook salmon
(Canadian Science Publishing, 2022-12-05) Buckner, Jack H; Satterthwaite, William H; Nelson, Benjamin W; Ward, Eric J.
Fish in all the world’s oceans exhibit variable body size and growth over time, with some species or populations exhibiting long-term declines in size. These patterns can be caused by a range of biotic, abiotic, and anthropogenic factors and impact the productivity of harvested populations. Within a given species, individuals often exhibit a range of life-history strategies that may cause some groups to be buffered against change. One of the most studied declines in size at age has been in populations of salmon; Chinook salmon in the Northeast Pacific Ocean are the largest bodied salmon species and have experienced long-term declines in size. Using long-term monitoring data, we develop novel size and growth models to link observed changes in Chinook size to life history traits and environmental variability. Our results identify three distinct trends in size across the 48 stocks in our study. Differences among populations were correlated with ocean distribution, migration timing, and freshwater residence. We provide evidence that trends are driven by interannual variation in certain oceanographic processes and competition with pink salmon.
Lost in translation: understanding divergent perspectives on a depleted fish stock
(Canadian Science Publishing, 2022-11-07) Dean, Micah J.; Hoffman, William S; Buchan, Nicholas C; Scyphers, Steven B; Grabowski, Jonathan H
Fishers commonly disagree with stock assessment results, particularly when a stock declines and strict harvest controls become necessary. Such regulations alter fisher perceptions of stock dynamics, contributing to a divergence in perspectives. Some assessments have inconsistent terminal year values (retrospective patterns) which fuels distrust in scientific advice. When assessment and fishery perspectives disagree, independent surveys can help identify biases and interpret discrepancies. We examine fishery trends and assessment results for Atlantic cod in the Gulf of Maine, a stock which has declined for decades. Trends were compared to a scientific-industry cooperative trawl survey and a telephone survey of fisher perceptions. Trawl survey results generally corroborate the assessment perspective on population scale and decline, yet suggest a different view of the age structure. Fisher perceptions were at odds with the assessment and trawl survey and likely resulted from regulations that altered fisher behavior, causing catch rates to increase while the stock declined. Divergent perspectives may be an unavoidable consequence of fishery management, yet acknowledging the underlying mechanisms might help avoid future conflict.
Inverse method applied to autonomous broadband hydroacoustic survey detects higher densities of zooplankton in near-surface aggregations than vessel-based net survey
(Canadian Science Publishing, 2022-10-27) Dunn, Muriel; Pedersen, Geir; Basedow, Sünnje L.; Daase, Malin; Falk-Petersen, Stig; Bachelot, Loïc; Camus, Lionel; Geoffroy, Maxime
Throughout all oceans, aggregations of zooplankton and ichthyoplankton appear as horizontal sound scattering layers (SSLs) when detected with active acoustic techniques. Quantifying the composition and density of these layers is prone to sampling biases. We conducted a net and trawl survey of the epipelagic fauna in northern Norway (70˚N) in June 2018 while an autonomous surface vehicle equipped with a broadband echosounder (283-383 kHz) surveyed the same region. Densities from the autonomous hydroacoustic survey were calculated using forward estimates from the relative density from the net and trawl, and inversion estimates with statistical data-fitting. All four methods (net, trawl, acoustic forward and inverse methods) identified that copepods dominated the epipelagic SSL, while pteropods, amphipods and fish larvae were present in low densities. The density estimates calculated with the inverse method were higher for mobile zooplankton, such as euphausiid larvae, than with the other methods. We concluded that the inverse method applied to broadband autonomous acoustic surveys can improve density estimates of epipelagic organisms by diminishing avoidance biases and increasing the spatio-temporal resolution of ship-based surveys.
Economic Diversity of Maine's American Lobster Fishery
(Canadian Science Publishing, 2022-12-19) Dayton, Alexa M.; Tokunaga, Kanae
Maine’s coastal communities critically depend on the American Lobster fishery, which is now exposed to ocean warming. There is uncertainty about the future robustness of the stock and the economic performance of the fleet appears vulnerable. This research characterizes economic heterogeneity in Maine’s fishing fleet using latent class stochastic profit frontier analysis. We explore the diversity of business models and examine how they were associated with the economic performance of the fleet in the pre-warming period. The study uses unique firm-level data that captures the operational and economic information of the harvesters in the year 2010, the year before the reported environmental change in the Gulf of Maine. Our findings indicate economic efficiencies differed based on their choice of business models and found technical upgrades generally contributed to improved economic performance in the pre-warming period. Reported societal benefits associated with employment levels have characterized the lobster production environment over firm-level efficiency. This research establishes a critically important baseline for future comparison and quantification of policy reforms within the U.S. lobster fishery.
Nature or nurture: A genetic basis for the behavioral selection of depth in siscowet and lean lake charr (Salvelinus namaycush) ecomorphs
(Canadian Science Publishing, 2022-11-14) Goetz, Frederick; Sitar, Shawn P; Seider, Michael; Jasonowicz, Andrew
Leans and siscowets are lake charr ecomorphs in Lake Superior that exhibit distinct depth selection behavior in the wild with leans occupying shallow (
Effects of freshwater residence time on reproductive success in anadromous alewife (Alosa pseudoharengus): climate change implications
(Canadian Science Publishing, 2022-11-07) Marjadi, Meghna N.; Roy, Allison H; Devine, Matthew T; Gahagan, Benjamin I.; Jordaan, Adrian; Whiteley, Andrew R; Rosset, Julianne
Earlier spring warming and anadromous fish migrations prompted by climate change are linked to shorter freshwater residency. Impacts of phenological change on anadromous fish populations are poorly understood with limited studies focused on iteroparous non-salmonids. We assessed freshwater residence time and reproductive success in an iteroparous clupeid, alewife (Alosa pseudoharengus) using a pedigree analysis and otolith-based spawning dates from captured juveniles. The primary objectives were to 1) estimate adult spawning duration in a freshwater pond (freshwater residence time) and 2) evaluate adult freshwater residence time, arrival date, length, sex, and reproductive success across two years in one system. Estimated freshwater residence times varied widely (1-64 days), and longer residence times were associated with earlier arrival dates, higher reproductive success, and more mating events. Longer freshwater residence times may allow alewife to spawn with more mates, produce more gametes, and experience a range of spawning and nursery conditions. Plasticity in alewife freshwater residence time could support earlier and shorter migration periods, but may result in lower reproductive output if adults spend less time in freshwater ponds.
Tributary streams provide migratory fish with access to floodplain habitats in a regulated river: evidence from alligator gar, Atractosteus spatula
(Canadian Science Publishing, 2022-10-14) Roberts, Hayden; Acre, Matthew R; Claus, Maximiliaan; Kappen, Florian; Winemiller, Kirk O; Daugherty, Daniel; Perkin, Josh
Migratory fishes with periodic life history strategies are sensitive to river regulation. Populations of these fishes may persist in highly regulated rivers by using tributaries that provide access to intermittently connected spawning and early life stage habitat in floodplains. We analyzed system hydrology and associated movement of a long-lived periodic strategist, the alligator gar (Atractosteus spatula), in the Brazos River, Texas. We hypothesized that: 1) flow regulation on the mainstem has resulted in the reduction of flood pulses, but tributaries have been less altered; and 2) alligator gar migrate into tributaries during high flows and temperatures. Our analysis revealed that flood pulses were reduced in the mainstem but not in an adjacent, less regulated tributary where floodplain-inundating pulses now outnumber those in the mainstem. Using data from tagged fish, we derived statistical models predicting greater occurrence of alligator gar in tributaries when water temperature exceeded 25° C and mainstem discharge exceeded 400 cms. These results emphasize that movement into less regulated tributaries can mitigate impacts of river regulation on mainstem river populations of alligator gar.
Benefits of stocking fewer, but larger individuals with implications for native fish recovery
(Canadian Science Publishing, 2022-10-24) Fonken, Dale; M Conner, Mary M; Walsworth, Timothy E.; Thompson, Paul
Artificial propagation is commonly used to reduce extinction risk for native, imperiled fish species. Thus, identifying stocking strategies that most effectively augment adult abundance is a critical aspect of successful adaptive management. The threatened June Sucker (Chasmistes liorus), endemic to Utah Lake, Utah, USA, experienced major declines in abundance following extensive ecosystem degredation. Over 800,000 June Sucker were stocked from hatcheries, grow-out ponds, and refuge populations from 1990-2019 across a range of sizes and seasons. Here, we evaluated post-stocking survival of June Sucker using a Cormack-Jolly-Seber Model with three covariates: size at stocking, origin, and season. Survival was positively correlated with size at stocking, with evidence of a possible size-selective predation threshold between 200-300mm, and spring stocking appeared to produce higher survival rates than summer or fall. We also compared cost and benefit for stocking hatchery origin June Sucker at different sizes, finding that stocking fewer, but larger (age-2) individuals was more cost-effective than stocking more, but smaller (age-1) individuals. Our results highlight operational changes that can help maximize efficacy of native fish hatchery programs.
Developing a Framework to Estimate Dynamic Reference Points for American Lobster Using a Thermally Explicit Spawning Stock Biomass / Recruitment Relationship
(Canadian Science Publishing, 2022-06-21) Hodgdon, Cameron Tyler; Shank, Burton; Chen, Yong
Management of marine species often relies on biological reference points (BRPs): threshold and target indicators that trigger management actions. These BRPs are usually based on the biology of the species and rarely consider environmental effects. Under climate change, this is problematic as many biological/physiological relationships are assumed temporally static. This spurious assumption can lead to inaccurate management practices. To combat this problem, recent research highlights the importance of developing temporally dynamic BRPs. This paper sees the development of a dynamic BRP calculator to inform management of levels of spawning biomass necessary to sustain the desired future levels of recruitment given forecasted climate scenarios. We test this calculator on American lobster of the Gulf of Maine and Georges’ Bank. Results for lobster indicate a temperature-driven, but complex, spawning biomass/recruitment relationship. Increased warming scenarios appear to yield overall higher recruitment per spawning biomass and dynamic BRPs calculated under these scenarios reveal that smaller population levels can sustain management-desired recruitment levels. This study highlights the importance of developing dynamic BRPs for fisheries management in a changing environment.

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