Pierre Dumont

Downstream migration of juvenile European sturgeon Acipenser sturio L. in the Gironde estuary

The European sturgeon (Acipenser sturio) is an endangered diadromous fish species that spawns in the rivers in late spring and early summer. The juveniles spend their first years in the brackish waters (5‰ to 25‰) of the estuary zone before moving out to sea. This study describes the downstream migration pattern of juvenile sturgeon, belonging to the 1994 cohort, the only one born naturally in the Gironde basin, France since the end of the 1980s. During October 1994 to December 1996 the inland section of the Gironde estuary was sampled monthly by trawl (n=818 tows) and all European sturgeon caught (n=381) were marked and released. The first sturgeon of the 1994 cohort (TL=27 cm) were caught in early March 1995 in the zones furthest upstream. During their second fall of life, juveniles gradually acclimatized, and spread over a wide range of salinity conditions. A first incursion into marine water was also observed (at least for a few fish) by the end of the second winter. During this second period, sturgeon showed preference for two particular zones situated at 18 and 38 km, respectively, from the mouth of the estuary. These zones, belonging to two different salinity sectors of the estuary, did not appear to be any different to their neighbors with regards to depth and type of substrate. There were no significant size differences among estuarine zones. Seasonal movements of sturgeon seem to be motivated by a search for warmer temperatures. After a period of early acclimatization of 15 months, juvenile European sturgeon appear to be highly tolerant of salinity variations.

Evaluation of a Gastric Lavage Method for Sturgeons

Abstract Because of their threatened status, sturgeons (Acipenseridae) can no longer be sacrificed for stomach content analysis. We tested a nonlethal method of gastric lavage on Siberian sturgeon Acipenser baeri. The efficiency and harmlessness of the method were tested with four different volumes of food (10, 20, 30, and 40 cm3), each composed of brown shrimp Crangon crangon, Chironomidae, earthworm Lumbriscus terrestris, and sand goby Pomatoschistus minutus. The Siberian sturgeons were force-fed before the gastric lavage was performed. Some prey were recovered from all the sturgeons, and the average food item recovery rate from stomach contents was 67.5%; recovery of brown shrimp and sand goby (78.2%) was greater than that of vermiform items (51.4%). The volume of food had no significant influence on the prey recovery rate. No mortality resulted from the gastric lavage. However, the method is not totally benign because the fish that had undergone gastric lavage averaged significantly greater weight los...

Do native predators feed on non-native prey? The case of round goby in a fluvial piscivorous fish assemblage

ABSTRACT We evaluated whether or not the invasive round goby (Neogobius melanostomus) represents an important prey source for seven native fish predators in Lake St. Pierre (St. Lawrence River, Canada). The frequency of occurrence of round goby in the stomach contents of brown bullhead (Ameiurus nebulosus) and channel catfish (Ictalurus punctatus) was very low (<5%), while for the five other predators, it varied between 22% (yellow perch; Perca flavescens) and 65% (sauger; Sander canadensis). Several competing models linking the probability of occurrence of round goby in stomach contents to variables related to space, physical habitat, biotic interactions and predator size were tested for the five species feeding on round goby. Results indicated that space variables influenced round goby occurrence in stomachs for all species. In addition, physical habitat variables had an influence for sauger and walleye (Sander vitreus); biotic variables had an influence for yellow perch, walleye and sauger; and size had an influence for northern pike (Esox lucius), smallmouth bass (Micropterus dolomieu) and walleye. These results are discussed in light of known biological features of the round goby and native predators studied here and have important implications in terms of understanding round goby invasion success in the Great Lakes-St. Lawrence system.

Is chemical contamination responsible for the decline of the copper redhorse (Moxostoma hubbsi), an endangered fish species, in Canada?

The copper redhorse (Catostomidae: Moxostoma hubbsi) is an endangered fish species whose worldwide distribution is limited to the St. Lawrence River and three of its tributaries, in Canada. Severe reproductive impairment and lack of successful recruitment reported in this species have been hypothetically associated with water pollution. In order to obtain an initial description of contamination levels in copper redhorse, seven accidentally-killed specimens from the Richelieu River were analyzed for trace metals, organochlorine pesticides, chlorobenzenes, PAHs, PCBs, dioxins and furans. Fish varied between 9 and 33 years of age, which corresponds to mature individuals. The levels of contaminants analyzed in different body tissues were close to and often lower than levels reported in other catostomid fish species from nearby locations within the St. Lawrence River basin. Concentrations of total mercury, cadmium and co-planar PCBs increased with fish age. The types and concentrations of contaminants found suggested that the Richelieu River spawning population of copper redhorse would migrate and spend time in the St. Lawrence River. Concentrations of many contaminants were often highest in gonadal tissues, but levels were much lower than reported in the literature as causing reproductive impairment or egg and fry mortality in fish. Further research is needed to assess the potential link between contaminants and reproductive failure in this endangered fish species.

First record of migrating silver American eels (Anguilla rostrata) in the St. Lawrence Estuary originating from a stocking program

ABSTRACT In fall 2009, six migrating silver American eels (Anguilla rostrata) originating from a stocking program were caught in the brackish waters of the St. Lawrence Estuary. These maturing eels were all females with gonads developed at a similar stage as other migrating eels in the estuary. Fluorescent Oxytetracycline marks observed on the otoliths allowed us to assert without any doubt that they came from glass eels caught in Nova Scotia and stocked 4 years earlier in the Richelieu River, 500 km upstream from the recapture location. Their length varied between 570 and 668 mm, which is within the size range of naturally recruited female silver eels in Nova Scotia, while silver eel are most generally longer than 80 cm in the St. Lawrence estuary. Their growth rate was also exceptionally fast. This direct observation is the first evidence that American eels stocked as glass eels can migrate seaward at least as far as the estuary in synchrony with naturally recruited female silver eels en route to their spawning grounds in the Sargasso Sea.

Assessment of Fat Reserves Adequacy in the First Migrant Silver American Eels of a Large-Scale Stocking Experiment

AbstractAn experimental stocking program in the St. Lawrence River–Lake Ontario system provided a unique opportunity to compare reproductive fitness of migrant silver American Eels Anguilla rostrata from the stocking program (SM) and wild migrants (WM), both of which were grown in the same location. Body size, muscle lipid stores, oocyte development, and morphometric indices of silvering were compared between SM and WM eels captured in the St. Lawrence River estuary. Migrant eels from the stocking program were smaller than wild migrants from the estuary, but their size was similar to migrating wild silver American Eels from their site of original capture on the Atlantic coast of New Brunswick and Nova Scotia. A bioenergetic model was used to estimate the costs of migration and reproduction and the duration of migration. The adequacy of the measured lipid reserves to meet these estimated energetic costs was assessed for SM and WM eels. Gonad maturation and stage of silvering for SM eels were less advanced ...

Swimming activity and energetic costs of adult lake sturgeon during fishway passage.

ABSTRACT Fish migrations through riverine systems can be energetically demanding, and the presence of fishways to facilitate upstream passage can add an additional energetic cost that may directly affect fitness. Successful fishway passage is a function of the ability of fish to select appropriate paths and swimming strategies that do not exceed their swimming capacity. Triaxial accelerometers were used to estimate the energetic expenditure of adult lake sturgeon (Acipenser fulvescens) swimming through a vertical slot fishway, to determine whether individual behaviour or path selection, resulting in differences in cumulative energy use, explain fishway passage success. Most individuals attempted to pass the fishway (n=30/44; 68%), although successful passage only occurred for a subset of those attempting (n=7/30; 23%). High-speed swimming was rarely observed during upstream passage through fishway basins, and was of short duration. Two turning basins delayed passage, subsequently resulting in a higher energetic cost. The rate at which energy was expended did not differ among successful and unsuccessful individuals, although successful sturgeon exhibited higher costs of transport (42.75 versus 25.85 J kg−1 m−1). Energy expenditure metrics were not predictive of successful fishway passage, leading us to conclude that other endogenous or exogenous factors influence passage success. In a practical application of field measurements of energy expenditure, we demonstrate that fishway passage through a structure designed to facilitate migration does result in an energetic loss for lake sturgeon (3249–16,331 J kg−1), equivalent to individuals travelling 5.8–28.2 km in a lentic system. Highlighted Article: Adult sturgeon energy use during fishway passage reveals location-specific differences in energy use and variable overall net energy costs.

Comparative Physiology and Relative Swimming Performance of Three Redhorse (Moxostoma spp.) Species: Associations with Fishway Passage Success*

Our understanding of biological criteria to inform fish passage design is limited, partially due to the lack of understanding of biological motivators, cues, and constraints, as well as a lack of biological performance evaluations of structures once they are built. The Vianney-Legendre vertical slot fishway on the Richelieu River, Quebec, Canada, passes large numbers of migrating redhorse (Moxostoma spp.) upriver to spawning grounds each year. We evaluated the physiological capacity and relative swimming ability of three redhorse species (Moxostoma anisurum, Moxostoma carinatum, Moxostoma macrolepidotum; silver, river, and shorthead redhorse, respectively) to determine how these biotic factors relate to variation in fishway passage success and duration. Shorthead redhorse had higher maximum metabolic rates and were faster swimmers than silver and river redhorse at their species-specific peak migration temperatures. Blood lactate and glucose concentrations recovered more quickly for river redhorse than for silver and shorthead redhorse, and river redhorse placed second in terms of metabolic recovery and swim speed. Interestingly, fish sampled from the top of the fishway had nearly identical lactate, glucose, and pH values compared to control fish. Using passive integrated transponders in 2010 and 2012, we observed that passage success and duration were highly variable among redhorse species and were not consistent among years, suggesting that other factors such as water temperature and river flows may modulate passage success. Clearly, additional research is needed to understand how organismal performance, environmental conditions, and other factors (including abundance of conspecifics and other comigrants) interact with fishway features to dictate which fish will be successful and to inform research of future fishways. Our research suggests that there may be an opportunity for a rapid assessment approach where fish chased to exhaustion to determine maximal values of physiological disturbance are compared to fish sampled from the top of the fishway, which could reveal which species (or sizes of fish) are approaching or exceeding their physiological capacity during passage.

Introduced Salmonids: Where are They Going in Quebec Watersheds of the Saint-Laurent River?

Abstract Salmonid fish (Salmonidae) are among the most important sport and commercial species in North America. Numerous attempts to extend their range have been made over the past 100 years. In Canada, Quebec was among the first provinces to be involved in such attempts. Rainbow trout (Salmo gairdneri), brown trout (S. trutta), cutthroat trout (S. clarki), kokanee (Oncorhyncus nerka), Arctic grayling (Thymallus arcticus) and huchen (Hucho hucho) were experimentally introduced in various lakes and rivers of the southern part of the province. Some of these species, along with pink (O. gorbuscha), chinook (O. kisutch), and coho salmon (O. tshawytscha), were also stocked intensively in neighbouring states and provinces. Rainbow, brown, and cutthroat trout species are now established in southern Quebec. Present data also indicate that rainbow and, to a lesser extent, brown trout gradually increased in numerous rivers flowing into the Gulf of Saint-Laurent, along the North Shore and the Gaspe Peninsula. Pink s...

Parasites of Illegally Introduced Tench (Tinca tinca) in the Richelieu River, Quebec, Canada

Abstract The tench (Tinca tinca) was introduced illegally into Quebec, Canada, in aquaculture operations in 1986. The fish escaped into the Richelieu River in the early 1990s and has since established a reproducing population. Nine of 10 fish sampled in 2000 were infected with parasites, including Raphidascaris acus (80%), Ergasilus megaceros (60%), larval Valipora campylancristrota (20%) and larval Proteocephalidae (20%). The tench were infected with fewer parasite species than those in its native range, in accordance with the enemy escape hypothesis. The copepod E. megaceros is a new Canadian record, with tench being a new host record. Intensity of E. megaceros was positively related to fish weight. It is suggested that V. campylancristrota, a potentially pathogenic metacestode, may be an introduced species that arrived with the tench, although other possible sources of introduction are discussed. The concomittant introduction of the fish and the parasite V. campylancristota may pose a threat to the copper redhorse (Moxostoma hubbsi), an endangered species found almost exclusively in the Richelieu River.