Estuary Fish Inventory Network – Data Information
Terrain
The inventory of ichthyology communities found in both the fluvial and middle estuary is performed by means of fixed traps used for eel fishing. Depending on the sites, the sampling period begins approximately in late April and usually runs until late October. In addition, at the beginning of the sampling period, a thermograph is installed in order to record the water temperature throughout the extent of the data collection period (except at the St. Nicolas site1). Once or twice a day, a sampler visits the fixed trap during low tide in order to count the number of fish caught in the fishing rig. The sampler also identifies the fish species before setting them free. Each week (every two weeks for the Saint-Nicolas station), a certain tide is chosen during which the sampler collects and freezes all the fish captured for laboratory analysis.
1 Data for temperature readings from the Saint-Nicolas site is provided by the water filtration plant of the city of Lévis.
History of weir fishing
The invention of weir fisheries dates back to a very distant time (Roy et al. 1977). In fact, in Canada, it is apparent that long before the first Europeans arrived, indigenous peoples already used this method of fishing. As early as the 1600s, both historians and explorers mentioned in their travel accounts the observation of such devices among Native Americans. It is believed that during the 17th century, the first French settlers while settling along the south shore of the St. Lawrence were quick to build and erect weir fisheries in order to exploit the riches the St. Lawrence and its tributaries had to offer. Over time, more and more families also established themselves on the banks of the St. Lawrence in order to live from fishing. Originally, the netting leaders forming the weir fishery were made of interlaced willow or alder creating a barrier preventing fish from escaping. For practical reasons, over the past 50 years, weir fisheries have gradually given way to the usage of fixed hatches; the latter being comprised of a metallic mesh or a wall like net lining. Nowadays, some fishing rigs, which have been operated from father to son, are still operational along the shorelines of the St. Lawrence.
Description and operation of the fixed trap
Every summer, stationary traps positioned at a perpendicular angle to the shore are installed within the intertidal zone. These fishing rigs, which have existed for centuries, are used to capture the American eel during its migration. Furthermore, these devices also allow for the capture of a wide variety of fish.
From a technical standpoint, the fixed traps are formed of one or more netting leaders and one or more containment boxes. They are positioned alternately in a zigzag pattern forming a funnel for each containment box (see adjoining figure). When the tides rise, in tow with the current, the fish follow the mesh linings of the fishing rigs and find themselves trapped inside the containment boxes where they are later recovered by fishermen.
Laboratory analysis
During the assessment phase, the data transmitted by the samplers are first verified and validated in a laboratory setting, then, depending on species (see chart below), biometric data such as length and weight are compiled. Some calcified structures are collected in order for specimen age analysis (scales, gill covers, otoliths, etc. [see photo below]). Gender as well as maturity stages are also determined for some of the specimens collected. In addition, the observation of specimen pathologies (deformities, erosions, lesions and tumors [see photo below]) is documented and sent to a veterinary laboratory for analysis. Each year, in collaboration with the ministère du Développement durable, de l’Environnement de la Faune et des Parcs, a specimen listing is established beforehand and used for the analysis of fish tissue in order to detect the presence of such contaminants as PCBs and heavy metals.
All data collected in the field and in the laboratory are entered into a database created specifically for that purpose. Subsequently, these data are used to, among others things, assess the specific composition of each of the sites as well as the relative abundance of fish encountered at different locations. The relative abundance in this case represents the measure of the total number of individuals of a given species compared to the total catch in a covered territory.
All data collected in the field and in the laboratory are entered into a database created specifically for that purpose. Subsequently, these data are used to, among others things, assess the specific composition of each of the sites as well as the relative abundance of fish encountered at different locations. The relative abundance in this case represents the measure of the total number of individuals of a given species compared to the total catch in a covered territory.
Conclusion
After only four years of operations, the EFIN has made it possible to inventory hundreds of thousands of fish, once or twice daily, on four different sites, covering a wide spatiotemporal window. It has also allowed to measure the status of fish within the St. Lawrence Estuary communities, assess species diversity, profile the different communities of interest for sportfishing (age and size structures), as well as help to estimate their abundance fluctuations in a continuous and standardized manner.
Description of sampling stations
In recent decades, eel stocks of the St. Lawrence Estuary have dramatically declined, to such a level that the Quebec government decided to implement a voluntary retirement program for fishing outfits. Since the reacquisition of the fishing rights campaign, launched in 2009 by the Ministère des Ressources Naturelles du Québec (MRNF), only about forty fishing outfits are still authorised to fish.
The Cap-Santé station, which is located on the north shore of the St. Lawrence, was formerly operated by a commercial fisherman who forsook his rights to renew his eel fishing license in 2009. The station is now operated by a wildlife technician hired by the MRNF.
The scientific fishing station in Saint-Nicolas is owned and operated by the Aquarium du Québec. This fishery, in operation since 1964 and located on the south shore of the St. Lawrence just upstream from the Pierre Laporte Bridge, has allowed gathering of important amounts of data annually regarding the St. Lawrence fish communities.
Sampling operations for the Saint-Irénée and Rivière-Ouelle stations are performed by commercial fishermen (eel and/or herring and capelin …) who conduct inventories for the daily catches found within their own fishing outfits. Both stations are located respectively on the north and south shores of the St. Lawrence.
