Post-stocking movement and survival of hatchery-reared bloater (Coregonus hoyi) reintroduced to Lake Ontario

1. Determining the movement and fate of fishes post-stocking is challenging due to the difficulty in monitoring them, particularly immediately after release. Bloater (Coregonus hoyi; Salmonidae) is a deepwater cisco that has been extirpated from Lake Ontario for several decades and is presently the focus of binational restoration stocking efforts; however, there is limited information to evaluate the efficacy of these efforts. The aim of this study was to examine the initial post-release survival, 3D movement, and behaviour of hatchery-reared bloater stocked in Lake Ontario to expand knowledge of post-stocking ecology of fish and inform stocking practices for deepwater ciscoes.
2. In total, 74 hatchery-reared bloater were tagged with acoustic transmitters with depth and temperature sensors in 2016, 2017, and 2018 and passively monitored on an array of 105 69-kHz acoustic receivers deployed in north-eastern Lake Ontario. Several spatial metrics analysed movements after release to investigate immediate post-stocking survival and behaviour for the first time in a pelagic freshwater forage fish.
3. Estimated survival for tagged bloater was low (≤42%) and detection periods of live bloater ranged from 0.2 to 12.1 days (mean ± SD: 2.9 ± 2.9 days). Following release, tagged bloater dispersed quickly and exhibited an association with deeper water (>40 m). Despite overlap in space use for some bloater, there was no evidence of schooling behaviour. Bloater underwent extensive diel vertical migration from near bottom to within metres of the surface. These results demonstrated that, despite high initial mortality, some hatchery-reared bloater survived the initial stress of release and displayed characteristic behaviour of the species.
4. This study demonstrated the value of acoustic telemetry in restoration efforts and revealed survival and behaviour of bloater that has never been observed at this resolution, providing novel information for the management of reintroduced species. Establishment of a self-sustaining population of bloater will help restore fish native to Lake Ontario thus increasing prey fish diversity, improving ecological integrity and resilience, and serving as a model for the reintroduction and management of other native species throughout the Great Lakes.

     

Real‐time PCR identification of lake whitefish Coregonus clupeaformis in the Laurentian Great Lakes

The purpose of this study was to develop a real‐time PCR assay to specifically identify lake whitefish Coregonus clupeaformis in larval fish assemblages based on a 122 bp amplicon from the mitochondrial genome. The efficiency of the reaction, as calculated from the standard curve, was 90·77% with the standard curve having an r² value of 0·998. Specificity of the assay provided single melt peak in a melt‐curve analysis and amplification of only the target species. The assay successfully identified target DNA in as low as 0·1% proportion of a DNA mixture. This assay was designed on the portable Smart Cycler II platform and can be used in both field and laboratory settings to successfully identify C. clupeaformis.     

Empirical evaluation of phenotype–environment correlation and trait utility with allopatric and sympatric whitefish, Coregonus lavaretus (L.), populations in subarctic lakes

Adaptive phenotypic divergence of sympatric morphs in a single species may have significant evolutionary consequences. In the present study, phenotypic impacts of predator on zooplankton prey populations were compared in two northern Finnish lakes; one with an allopatric whitefish, Coregonus lavaretus (L.), population and the other with three sympatric whitefish populations. First, we examined whether there were phenotypic associations with specific niches in allopatric and sympatric whitefish. Second, trait utility (i.e. number of gillrakers) of allopatric and sympatric whitefish in utilizing a pelagic resource was explored by comparing predator avoidance of prey, prey size in environment, and prey size in predator diet. The allopatric living large sparsely rakered (LSR) whitefish morph, was a generalist using both pelagic and benthic niches. In contrast, sympatric living whitefish morphs were specialized: LSR whitefish was a littoral benthivore, small sparsely rakered whitefish was a profundal benthivore and densely rakered (DR) whitefish was a pelagic planktivore. In the lake with allopatric whitefish, zooplankton prey did not migrate vertically to avoid predation whereas, in the lake with sympatric whitefish, all important prey taxa migrated significantly. Trait utility was observed as significantly smaller size of prey in environment and predator diet in the lake with DR whitefish than in the lake with only LSR whitefish.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 561–572.     

Diel and seasonal patterns of food intake and prey selection by Coregonus sp. in re-oligotrophicated Lake Lucerne, Switzerland

Feeding intensity by whitefish Coregonus sp., in oligotrophic Lake Lucerne in Switzerland was high during dusk when the bulk of potential prey items were in the depth zone occupied by the fish. Diet composition was fairly uniform throughout the day but changed substantially over the seasons. The fish fed opportunistically; differences between seasons reflected changes in prey availability. During the intensive feeding and growing period (May-September), fish were found in the upper 20 m of the lake feeding primarily on cladocerans. Large and non-evasive species, Daphnia spp. and Bythotrephes longimanus , were the most numerous and frequent organisms in the diet during the major part of the growing season. Smaller ( Bosmina spp.) as well as evasive species (cyclopoid copepods) were consumed in large numbers when larger, non-evasive species were rare in the lake. The fish showed strong preference for the least abundant crustacean, B. longimanus , while the most abundant crustaceans, calanoid copepods, were rare in the diet. The fish not only selected particular species but, within each species, selected the larger individuals. Diel vertical migration of the prey items in this lake could be, at least in part, attributed to fish predation pressure. The observed selectivity patterns shown by the fish are explained in terms of prey visibility, escape ability, the overlap in distribution of predators and prey in time and space, the profitability of the prey and the present trophic state of the lake.     

Distribution and habitat of Nitellopsis obtusa (Characeae) in the Laurentian Great Lakes

Nitellopsis obtusa, a macroalga (Characeae) native to Europe and Asia, was found in U.S. waters of the St. Clair-Detroit River system in 1983, thus extending the range of this taxon into the Laurentian Great Lakes about 850 km from the St. Lawrence River where it was first discovered in North America in 1978. Its occurrence only in water frequented by commercial shipping vessels suggests that it is distributed via this mechanism. In the St. Clair-Detroit River system, N. obtusa was collected with a Ponar grab at four locations, and with a grapnel at one additional location. It was the ninth most frequently found macrophyte and it was most abundant at Belle Isle in the Detroit River, where the mean dry-weight biomass in Ponar samples was 0 g m^-2 in June, 37 g m^-2 in August, and 32 g m⁻² in September. Maximum biomass of this taxon in one Ponar grab at this location was 289 g m^-2 in September. The alga occurred primarily in water of relatively low current velocity (11.3 cm s⁻¹) and in association with Vallisneria americana, Myriophyllum spicatum, Potamogeton richardsonii, Najas flexilis, and Elodea canadensis. Contribution 654, Great Lakes Fishery Laboratory, Ann Arbor, MI 48105, USA Contribution 654, Great Lakes Fishery Laboratory, Ann Arbor, MI 48105, USA     

Population ecology, vertical migration and feeding of the Ponto-Caspian invader Hemimysis anomala in a gravel-pit lake connected to the River Rhine

1. The Ponto‐Caspian invader, Hemimysis anomala, was recently found in large numbers in a gravel‐pit lake connected to the Lower Rhine. Mysids were sampled with Perspex traps between September 2002 and April 2003 to study the population dynamics, vertical migration and feeding. 2. The abundance (as catch per unit effort, CPUE) of H. anomala declined from 270 individuals (ind.) trap^?1 (4 h)^?1 in December to below 4 ind. trap^?1 (4 h)^?1 in April. Average lengths ranged from 4.9 mm in autumn to 9.9 mm in March. The length–weight relationship of virgin females changed throughout the sampling period, from a size‐corrected wet weight of 5.1 mg in September to 16.6 mg in April for a female of 7.8 mm. 3. Successive monthly samples taken over 24 h revealed that H. anomala preferred the surface at twilight and night. During dawn the mysids migrated to the middle and bottom layers and were hardly found during day. Diel vertical migration clearly depends on the proximate factor light. 4. Stomach analyses revealed that larger H. anomala preferred zooplankton, whereas small individuals fed more on phytoplankton. The seasonal comparison showed an increasing percentage of zooplankton with increasing length. The proportion of zooplankton in the stomachs of large H. anomala individuals was highest during night and lowest during day. 5. The results suggest that H. anomala may become an important link between primary/secondary production and higher trophic levels in the food web of its new environments at the Lower Rhine.     

Hybridization of Cyprinus carpio and Carassius auratus,the first two exotic species in the lower Laurentian Great Lakes

Synopsis A preliminary comparison of Cyprinus carpio × Carassius auratus hybrids with the parent species is made by means of hybrid indices for 29 morphometric and 19 meristic characters. Of these 48 characters 29 were intermediate, seven were identical with one of the parents and 12 were extreme. Marked osteological differences in the crania of the parent species were noted as possible diagnostic characters for the identification of hybrids.Note     

Potential changes to the biology and challenges to the management of invasive sea lamprey Petromyzon marinus in the Laurentian Great Lakes due to climate change

Control programs are implemented to mitigate the damage caused by invasive species worldwide. In the highly invaded Great Lakes, the climate is expected to become warmer with more extreme weather and variable precipitation, resulting in shorter iced‐over periods and variable tributary flows as well as changes to pH and river hydrology and hydrogeomorphology. We review how climate change influences physiology, behavior, and demography of a damaging invasive species, sea lamprey (Petromyzon marinus), in the Great Lakes, and the consequences for sea lamprey control efforts. Sea lamprey control relies on surveys to monitor abundance of larval sea lamprey in Great Lakes tributaries. The abundance of parasitic, juvenile sea lampreys in the lakes is calculated by surveying wounding rates on lake trout (Salvelinus namaycush), and trap surveys are used to enumerate adult spawning runs. Chemical control using lampricides (i.e., lamprey pesticides) to target larval sea lamprey and barriers to prevent adult lamprey from reaching spawning grounds are the most important tools used for sea lamprey population control. We describe how climate change could affect larval survival in rivers, growth and maturation in lakes, phenology and the spawning migration as adults return to rivers, and the overall abundance and distribution of sea lamprey in the Great Lakes. Our review suggests that Great Lakes sea lamprey may benefit from climate change with longer growing seasons, more rapid growth, and greater access to spawning habitat, but uncertainties remain about the future availability and suitability of larval habitats. Consideration of the biology of invasive species and adaptation of the timing, intensity, and frequency of control efforts is critical to the management of biological invasions in a changing world, such as sea lamprey in the Great Lakes.     

Neutral markers, ecologically relevant traits, and the structure of genetic variation in Daphnia

Zooplankton, Daphnia in particular, are increasingly used as model organisms to investigate general evolutionary biological questions. I here discuss some recent insights into the patterns and processes determining genetic diversity within and genetic differentiation among natural populations of cyclically parthenogenetic Daphnia. I focus on three aspects: (1) the interplay of phenotypic plasticity and genetic polymorphism in explaining variability in ecologically relevant traits, (2) the patterns of genetic variation revealed by neutral markers and ecologically relevant traits, and (3) the evolutionary ecological importance of hybridization events in Daphnia. The need for studies on the evolutionary ecology of sexual reproduction and dispersal via ephippial eggs in Daphnia is stressed.     

Estimating phosphorus retention of existing and restored coastal wetlands in a tributary watershed of the Laurentian Great Lakes in Michigan,USA

Simulation modeling with uncertainty analysis was applied to the question of nonpoint source pollution control through extensive wetland restoration. The model was applied to the Quanicassee River basin, a tributary stream to Saginaw Bay on Lake Huron in northeastern Michigan, USA. An estimate of the role of the existing 695 ha of riverside and lake-side wetlands in the lower Quanicassee River basin suggests that they retain 1.2 metric tons of phosphorus per year (mt P/yr), or 2.5% of the total phosphorus load from the basin. A simple Vollenweider-type model of phosphorus retention by created wetlands, calibrated with 3-years of data from two wetland sites in Midwestern USA, was used to estimate the effect of major wetland restoration in the basin. For a wetland restoration project involving 15% of the Quanicassee River basin or 3,120 ha of wetlands, an estimated 33 mt P/yr could be retained, assuming a proper hydrologic connection between the wetlands and the river. This would represent a reduction of two-thirds of the existing phosphorus load to the Bay from the Quanicassee River basin. Large-scale wetland restoration appears to be a viable management practice for controlling phosphorus and other nonpoint source pollution from entering Saginaw Bay. It is an alternative that meets two major resource goals – developing wetland habitat and controlling pollution to the Great Lakes.     

A scientific basis for restoring fish spawning habitat in the St. Clair and Detroit Rivers of the Laurentian Great Lakes

Loss of functional habitat in riverine systems is a global fisheries issue. Few studies, however, describe the decision‐making approach taken to abate loss of fish spawning habitat. Numerous habitat restoration efforts are underway and documentation of successful restoration techniques for spawning habitat of desirable fish species in large rivers connecting the Laurentian Great Lakes are reported here. In 2003, to compensate for the loss of fish spawning habitat in the St. Clair and Detroit Rivers that connect the Great Lakes Huron and Erie, an international partnership of state, federal, and academic scientists began restoring fish spawning habitat in both of these rivers. Using an adaptive management approach, we created 1,100 m² of productive fish spawning habitat near Belle Isle in the Detroit River in 2004; 3,300 m² of fish spawning habitat near Fighting Island in the Detroit River in 2008; and 4,000 m² of fish spawning habitat in the Middle Channel of the St. Clair River in 2012. Here, we describe the adaptive‐feedback management approach that we used to guide our decision making during all phases of spawning habitat restoration, including problem identification, team building, hypothesis development, strategy development, prioritization of physical and biological imperatives, project implementation, habitat construction, monitoring of fish use of the constructed spawning habitats, and communication of research results. Numerous scientific and economic lessons learned from 10 years of planning, building, and assessing fish use of these three fish spawning habitat restoration projects are summarized in this article.     

Effects of cyclic and constant hydrostatic pressure on norepinephrine and epinephrine levels in the brain of flounder

The effects of cyclic and constant hydrostatic pressure on the norepinephrine and epinephrine content in discrete regions of the brain of European flounder Platichthys flesus were studied. After a 14 day exposure to cyclic hydrostatic pressure with a tidal period of 12·4 h and with a maximum peak of 800 kPa (range 200–800 kPa of absolute hydrostatic pressure), fish showed a highly significant decrease in norepinephrine content when compared to control animals held at constant atmospheric pressure. No changes were detected in fish submitted to a constant hydrostatic pressure of 800 kPa.     

Diel migration and vertical distribution of Cladocera in Lake D. Helvecio (Minas Gerais,Brazil)

Six genera of Clad ocera (Diaphanosoma, Daphnia, Ceriodaphnia, Moina, Bosmina, Bosminopsis), each of them usually with only one species were found in Lake D. Helvecio, a natural valley lake located in the eastern part of Brazil. Diurnal migratory movements of the organisms observed in this lake showed a different pattern in different species. Closely related species, which explore the same food source, live in different layers, thus avoiding interspecific competition. The migratory behaviour of the species was studied mainly in relation to temperature and oxygen distribution in the lake. Thus, analyses were made in the summer (January, 1978) when a strong stratification occurs with the establishment of a thermocline and an oxycline. Comparisons were made also with the data obtained in winter (July, 1978), when a complete mixing of water occurs.     

Sediment toxicity testing in two areas of concern of the Laurentian Great Lakes: Toronto (Ontario) and Toledo (Ohio) Harbours

The impact of elutriated sediment-associated contaminants from Toronto and Toledo Harbours on ultraplankton (5–20 µm) and microplankton/netplankton (> 20 µm) carbon assimilation rates was determined using Algal Fractionation Bioassays (AFBs). All of the Toronto elutriate caused significant inhibition of ultraplankton carbon assimilation. The Toronto Site 2 elutriate caused the greatest significant inhibition (38 percent, p < 0.001) with a 20 percent dose of standard elutriate. Similarly, all Toledo elutriates caused significant inhibition of ultraplankton productivity. Toledo Site 2 elutriate was the most toxic with the 20 percent elutriate dose (35 percent, p < 0.001).The treatment of elutriates with Chelex-100 resin was used to remove dissolved free metal ions which, in some samples, resulted in the recovery of ¹⁴C assimilation. This was attributed to the elimination of the toxic effects of dissolved metals removed by the Chelex treatment. Residual toxicity after the Chelex treatment was ascribed to the high PCB levels observed in the sediment samples taken from both harbours and possibly to other organic contaminants. Due to the extreme sensitivity of the technique, an EC25 is proposed as an early warning indicator for applied use by regulatory agencies. Our procedure has been included amongst a battery of tests recommended by the International Joint Commission for monitoring areas of concern in the Laurentian Great Lakes.     

Broad- to fine-scale population genetic patterning in the smallmouth bass Micropterus dolomieu across the Laurentian Great Lakes and beyond: an interplay of behaviour and geography

Analysis of population genetic relationships reveals the signatures of current processes such as spawning behaviour and migration, as well as those of historical events including vicariance and climate change. This study examines these signatures through testing broad‐ to fine‐scale genetic patterns among smallmouth bass Micropterus dolomieu spawning populations across their native Great Lakes range and outgroup areas, with fine‐scale concentration in Lake Erie. Our primary hypotheses include whether genetic patterns result from behavioural and/or geographical isolation, specifically: (i) Are spawning groups in interconnected waterways genetically separable? (ii) What is the degree of isolation across and among lakes, basins, and tributaries? (iii) Do genetic divergences correspond to geographical distances? and (iv) Are historical colonization patterns from glacial refugia retained? Variation at eight nuclear microsatellite DNA loci are analysed for 666 smallmouth bass from 28 locations, including 425 individuals in Lake Erie; as well as Lakes Superior, Huron, and Ontario, and outgroups from the Mississippi, Ohio, St. Lawrence, and Hudson River drainages. Results reveal marked genetic differences among lake and river populations, as well as surprisingly high divergences among closely spaced riverine sites. Results do not fit an isolation‐by‐geographical‐distance prediction for fine‐scale genetic patterns, but show weak correspondence across large geographical scales. Genetic relationships thus are consistent with hypotheses regarding divergent origins through vicariance in glacial refugia, followed by colonization pathways establishing modern‐day Great Lakes populations, and maintenance through behavioural site fidelity. Conservation management practices thus should preserve genetic identity and unique characters among smallmouth bass populations.     

In situ grazing pressure and diel vertical migration of female Calanus euxinus in the Black Sea

Gut pigment and abundance of the female Calanus euxinus (Hulsemann) weremeasured from several water layers (defined by density values), with3–5 h intervals during 30 h and 21 h at a station in the southwesternBlack Sea in April and in September 1995, respectively. The female C.euxinus was observed to begin migration to the upper phytoplankton-richlayer approximately 3 or 4 hours before the sunset. Only a fraction of thefemale Calanus population (0.2% in April and 3.6% inSeptember) did not migrate but remained at the depth of the oxygen minimumzone during the nighttime. The migrating population was determined to havespent 7.5 h in the euphotic zone in April and 10.5 h in September. Thegrazing rate of female Calanus euxinus was measured from the gut contentdata collected from the layers which contain the euphotic zone. Thepercentage of primary production grazed by the female C. euxinus wascalculated as 14.5% in April and 9.5% in September. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contrasting migration behaviour of Daphnia pulicaria and D. galeata x hyalina, in avoidance of predation by 0+perch (Perca fluviatilis)

In spring and early summer, a small population of the large-bodied Daphnia pulicaria coexists with a much larger population of the medium-sized hybrid Daphnia galeata × hyalina in the epilimnion of Lake Maarsseveen (The Netherlands). When large shoals of juvenile perch (Perca fluviatilis) appear in the open water, both species start to migrate vertically. Since D. pulicaria has a larger body-size than D. galeata × hyalina, and is therefore competitive dominant over the hybrid, it is unlikely that both species interact via their common food resource, but they react both to fish predation. However, since they differ in size, and therefore in vulnerability for fish predation, both species adopt different strategies. The smaller bodied, and less vulnerable D. galeata × hyalina exhibits diel vertical migration ascending to the surface at dusk, and staying there during the night. In this way, benefiting from the higher temperatures of the surface layers. In contrast, the large-bodied, and more vulnerable D. pulicaria selects the deep cold hypolimnion water layers as refuge against fish predation. In this way it benefits from a safe habitat, free from fish predators, but on the other hand suffers from low water temperatures, which decrease its fitness. It is likely that the relatively higher temperature in the upper water layers serves as a proximate factor for the downward migration of D. pulicaria.     

Dispersal strategies, secondary range expansion and invasion genetics of the nonindigenous round goby, Neogobius melanostomus, in Great Lakes tributaries

Dispersal strategies are important mechanisms underlying the spatial distribution and colonizing ability of all mobile species. In the current study, we use highly polymorphic microsatellite markers to evaluate local dispersal and colonization dynamics of the round goby (Neogobius melanostomus), an aquatic invader expanding its range from lake to river environments in its introduced North American range. Genetic structure, genotype assignment and genetic diversity were compared among 1262 round gobies from 20 river and four lake sites in three Great Lakes tributaries. Our results indicate that a combination of short-distance diffusion and long-distance dispersal, collectively referred to as 'stratified dispersal', is facilitating river colonization. Colonization proceeded upstream yearly (approximately 500 m/year; 2005-2009) in one of two temporal replicates while genetic structure was temporally stable. Contiguous dispersal from the lake was observed in all three rivers with a substantial portion of river fish (7.3%) identified as migrants. Genotype assignment indicated a separate introduction occurred upstream of the invasion front in one river. Genetic diversity was similar and relatively high among lake and recently colonized river populations, indicating that founder effects are mitigated through a dual-dispersal strategy. The remarkable success of round goby as an aquatic invader stresses the need for better diffusion models of secondary range expansion for presumably sessile invasive species.     

Assemblage structure,vertical distributions and stable-isotope compositions of anguilliform leptocephali in the Gulf of Mexico

In August 2007, October 2008 and September–October 2010, 241 Tucker trawl and plankton net tows were conducted at the surface to depths of 1377 m at six locations in the northern and eastern Gulf of Mexico (GOM) to document leptocephalus diversity and determine how assemblage structure, larval size, abundance and isotopic signatures differ across the region and with depth. Overall, 2696 leptocephali representing 59 distinct taxa from 10 families were collected. Five families accounted for 96% of the total catch with Congridae and Ophichthidae being the most abundant. The top four most abundant species composed 59% of the total catch and included: Ariosoma balearicum, Paraconger caudilimbatus, Rhynchoconger flavus and Ophichthus gomesii. Four anguilliform species not previously documented in the GOM as adults or leptocephali were collected in this study, including Monopenchelys acuta, Quassiremus ascensionis, Saurenchelys stylura and one leptocephalus only known from its larval stage, Leptocephalus proboscideus. Leptocephalus catches were significantly greater at night than during the day. Catches at night were concentrated in the upper 200 m of the water column and significantly declined with increasing depth. Leptocephali abundances and assemblages were significantly different between sites on the upper continental slope (c. 500 m depth) and sites on the middle to lower continental slope (c. 1500–2300 m). Sites on the lower continental slope had a mixture of deep-sea demersal, bathypelagic and coastal species, whereas upper-slope sites contained several numerically dominant species (e.g., A. balearicum, P. caudilimbatus) that probably spawn over the continental shelf and upper slope of the GOM. Standard lengths of the four dominant species differed between sites and years, indicating heterochronic reproduction and potential larval source pools within and outside of the GOM. Stable-isotope analyses (δ¹³C and δ¹⁵N) conducted on 185 specimens from six families revealed that leptocephali had a wide range of isotopic values at the family and size-class levels. Species in the families Muraenidae, Congridae and Ophichthidae had similar δ¹⁵N values compared with the broad range of δ¹⁵N values seen in the deep-sea families Nemichthyidae, Nettastomatidae and Synaphobranchidae. Stable-isotope values were variably related to length, with δ¹⁵N values being positively size correlated in ophichthids and δ¹³C values being negatively size correlated in A. balearicum and P. caudilimbatus. Results suggest that leptocephali feed in various water depths and masses, and on different components of POM, which could lead to niche partitioning. Ecological aspects of these important members of the plankton community provide insight into larval connectivity in the GOM as well as the early life history of Anguilliformes.