© 2019 Aaron Fisk - Trophic Ecology Laboratory. All rights reserved

Lake Ontario Salmonids 

Background

Lake Ontario contains a diverse community of salmon and trout (salmonids). With six such species overlapping in their distributions, there is potential for competition among species for food resources and suitable habitat. Non-native Chinook salmon (Oncorhynchus tshawytscha), Coho salmon (Oncorhynchus kisutch), brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) have come to provide highly valuable recreational fisheries since their introduction to Lake Ontario in the 1960s. However, these non-native salmonids are sometimes perceived to be in conflict with efforts to restore native salmon and trout – specifically Lake Trout (Salvelinus namaycush) and Atlantic salmon (Salmo salar), owing to concerns about competition for food and suitable habitat. We only have a coarse understanding of the movements and habitat preferences of these species in Lake Ontario, owing to the inherent difficulty in studying fish movements in such a large system. Various research projects surround assessing the movements, and habitat and food resources utilized by Lake Ontario salmonids, however, they revolve around 3 major methodologies: data storage tags, stable isotopes and acoustic telemetry.

Data Storage Tags 

Pop-off data storage tags (pDSTs) first became available for use in freshwater in 2013 and provide a useful tool for collecting high-resolution data on depth and temperature preferences of fish in the wild. These tags (see photo), manufactured by Cefas Technology Ltd., are designed such that they can be externally attached to aquatic animals, record variables of interest at regular intervals, and subsequently pop-off the animal and float to the surface after a pre-programmed period of time. In Lake Ontario, we have now released 118 fish across three years (2014-2016) with externally-attached pDSTs. The tags are programmed to record the fish’s depth and temperature every 70s and to pop off the fish and float to the surface after approximately one year of data collection and storage. The tags do not transmit any information (i.e., they are data loggers, not transmitters), meaning that we rely on tags being found by members of the public and returned to us by mail so that we can download data from the tags for analyses. The bright orange colour of the tags increases the likelihood of them being found when floating on the surface or after having washed up on beaches. In addition to a $100 reward, interested citizens who find and return tags have also been sent ‘report cards’ with an example of the data from the tag they returned. For more information, click here

Relevant Lab Members – Graham Raby (PDF), Sarah Larocque (PhD)

Stable Isotopes 

Stable isotopes are a commonly used approach to infer long-term patterns of diet as opposed to stomach samples that provide a brief snap-shot of an organisms’ diet. Through coordinated sampling efforts binationally, stable isotope samples are collected on salmonids and the lower food web in Lake Ontario (and tributaries) over time. Stable isotopes can assist in the investigation of the trophic structure and overlap in diet among the salmonids. The ability to assess the trophic patterns in the salmonids can occur in both the lake as adults but also in the tributaries at the juvenile life stage. This is of particular interest for native species restoration as well as how diets reflect food web changes (i.e., changes in prey abundance and invasive species). With the aid of stable isotopes we can begin to investigate trophic niche overlap, as well as estimates on dietary proportions of the salmonids of Lake Ontario.

Relevant Lab Members – Sarah Larocque (PhD), James Mumby (MSc – alumni), Scott Colborne (PDF – alumni)

Acoustic Telemetry

Passive acoustic telemetry has been increasingly used to look at fish movements within the Great Lakes. With multiple collaborations and coordination through the GLATOS (Great Lakes Acoustic Telemetry Observation System) network, Lake Ontario has been increasing receiver coverage to better understand fish movements of various species (e.g., see Bloater page). As of 2017, Lake Ontario now has coverage in the western and eastern basins. To better understand the broad-scale movements of the salmonids, there have been a total of 34 salmonids that were angle and tagged (Chinook salmon, Coho salmon, rainbow trout, lake trout) in Lake Ontario (western basin), and 10 hatchery Atlantic salmon tagged and released into Lake Ontario (Bay of Quinte). As receiver coverage increases, as well as the number of tagged salmonids, we will begin to gain an understanding of home range, movement patterns, habitat use, among many other questions. We will also be able to combine the acoustic and data storage tag information to delve into more specific behavioural questions.

Relevant Lab Members – Sarah Larocque (PhD), Silviya Ivanova (PhD)