State and Tribal natural resource agencies provided in-kind contribution of staff hours, expenses, and equipment for the collection of fish stomachs from multiple length classes captured in their scheduled fish surveys, and stomach samples were frozen for subsequent laboratory analyses. Predator fish diets were analyzed at laboratories at Northern Michigan University (NMU) and Marquette Fisheries Research Station (MIDNR); prey fish diets were analyzed at the laboratory at Lake Superior State University. Unidentifiable larval and juvenile coregonines were taxonomically identified using Single Nucleotide Polymorphism genetic techniques.

The Minnesota DNR also collected diets from some predator fish via a cooperative angling program (the P3). We (Minnesota DNR) recognized quickly that some species would be underrepresented in the lake wide analyses because some species are rarely captured in our standardized lake survey assessments in Minnesota waters (e.g., Chinook, Coho, and Pink salmon). Who catches more salmonids than Minnesota DNR? ANGLERS! And so- the P3 was born! This study is still ongoing and much of the data and sample summaries are being worked on as we speak. The lake-wide results (Sitar et al.) should be summarized and available by December 2023.

P3 sample collection summary and interesting diet items: 2020-2023

A total of 4,515 fish carcasses were donated by volunteer P3 anglers over the last three years. From that, 4,408 stomachs from 15 different fish species were in good shape (i.e., not cut open or had diets removed), pre-processed (inventoried and bagged), and sent to NMU for diet analyses. The most samples were provided from the open-water season in 2021 (3,615), with less in 2022 (705) because we prioritized a “target sample list” based on the number, shore zone, and size-group of each species we needed to reach target sample sizes. Awesome work folks! The number of fish stomachs (diets) extracted from fish donated by anglers for the Minnesota DNR’s Predator Prey Project far exceeded expectation!

At least 68 individual anglers volunteered for the P3 project over the past three years, of which 66% (45) contributed at least one sample for this study. Participants were a mix of local charter captains and individual anglers. The most samples were provided by volunteer Angler ID 22, who had contributed 858 stomach samples over three years! The second most was volunteer Angler ID 61 with 480 total samples; this was not just one individual angler, but a bunch of anglers who harvested fish during the Silver Bay Salmon Classic in 2021 and 2022; the Minnesota DNR attended these events and collected samples at the cleaning station at Silver Bay Marina. A summary of carcasses provided by Angler ID is shown in Table 3.

Lake Superior Cisco: History is happening NOW!

Anyone who knows Lake Superior can understand how important prey are to predators in what seems to be a relatively infertile environment – and also how FEW prey there are in relation to the size of the waterbody! One of the most important prey for predator fish in Lake Superior is Cisco (also known as Tullibee or Lake Herring). I like to think of Cisco as Snickers bars – delicious snacks full of things that will make you fat and happy! Lake wide efforts to monitor the Lake Superior Cisco populations lake wide over time (via trawling on the RV Kiyi) has found that recruitment (number of small fish to replace the big ones) is an issue. Why? That story is complicated and one for another day.

Trawling data from the RV Kiyi in 2022 found that Cisco, particularly small-sized fish, are more abundant than we have seen in many DECADES! All previous diet studies have occurred in years when Cisco were much less abundant (or close to non-existent!). Therefore, we feel it is vitally important to continue with the Predator Prey Project in 2023 and help us understand what happens to this big year-class of Cisco over time. Will they survive? If not, what ate them- and when and where?