ePIKE - Monitoring of pike with eDNA

Experiments with pike 2019

Laboratory experiment with juvenile pike

The objective of this experiment was to:

1. Obtain eDNA-samples from pike to identify suitable primers (mtDNA, COI and 5S rDNA ITS)
2. Estimate DNA shedding and degradation rates
3. Determine the DNA-biomass relationship under controlled and nearly optimal conditions

Juvenile pike where caught in collaboration with the Swedish Angling Association “Sportfiskarna” in a nearby wetland in June 2019 and transported to aquaria at the institute of freshwater research, SLU, Drottningholm. After an acclimation period, we conducted a small scale experiment where different densities of juvenile pike (0, 1, 3, 9 individuals, 3 replicates each) were incubated in aquaria containing 15L filtered lake water. Water temperature and other environmental variables were monitored continuously. eDNA samples were collected by filtration through a 1.2 µm nitrocellulose filter at seven time points (before the addition of pike, during the incubation and after removal of pike).

Preliminary results from the experiment

Juvenile pike collected from the wild were successfully kept under laboratory conditions (in accordance with ethical permits). Individual isolation in Whitman-Vibert-boxes proved to be an effective method to prevent injuries and cannibalism when several individuals were kept together. The preliminary studies have provided valuable information and practical experience in stress-mitigation and survival of juvenile pike under laboratory conditions. Work analysing eDNA samples from the experiment and design of new 5S rDNA primer pairs is ongoing in collaboration with the Estonian University of Life Sciences in Tartu. .

Literature review

During 2019 we have conducted a comprehensive literature review which will be useful in the development of laboratory protocols and experimental designs.

Experiments with pike 2020

Fieldwork

We conducted a comprehensive collection of eDNA samples from the Stockholm Archipelago during spring. We collected water samples for eDNA analysis from 22 shallow bays during the pike spawning period (March-May). The collection of eDNA was synchronized with the hook-and-line fish survey within the ReFisk project. This will enable the comparison of different sampling methods. All eDNA samples are frozen and will be analysed during 2021. 

Laboratory experiment

During 2020, our team was reinforced by a new Master’s student – Ofír Svensson. At the experimental facility in Drottningholm we conducted a series of outdoor mesocosm experiments where pike of different sizes, ranging a few kg to approximately 10 kg were incubated in natural lake water to determine the DNA-biomass relationship in adult pike. We also studied the effect of pike densities on eDNA shedding and different combinations of filtration setups in order to optimize the sampling and DNA recovery. 

During autumn, we have moved into the lab where we are testing different DNA extraction methods with the aim to find a cost efficient, reliable and effective protocol which will be used to analyze the accumulated samples from mescosm experiments and the field. The winter months will therefore be primarily dedicated to analysis of collected samples, but also to planning!

During 2021 we will conduct yet another field study where we aim to study how the eDNA-signal fluctuates seasonally. More info to come!

Experiments 2021

Fieldwork

On March 17th we installed a fish counter in the wetland Hemmesta sjöäng east of Stockholm. The counter is mounted at the entrance of the wetland where it will count, measure length and film all fishes that moves in and out of the wetland. Link to the counter

During spring, as pike spawn we will besides monitoring the counter also take water samples for eDNA analyses continuously over the entire spring season. By doing so we can investigate if the amount of eDNA in the outflow from the wetland can be used to successfully describe the patterns of the spawning migration. Sampling is done in accordance with techniques we have developed in earlier parts of the project.

The study at Hemmesta is done in collaboration with the Swedish Angler Association and Värmdö county, whom also involve school students to manage the wetland within the project Skolbäcken. We are very happy about these collaborations and the synergistic effects at the local level. We are also grateful to the volunteers that have contributed in different ways. The fish counter comes from TiVA and the management of the website is operated by Fiskevårdsteknik.