From FishBase

Food items reported for Perca flavescens
n = 14
Food I Food II Food III Food name Country Predator Stage
zoobenthos benth. crust. amphipods unidentified amphipods Canada recruits/juv.
zoobenthos insects insects unidentified anisopteran nymphs Canada recruits/juv.
zoobenthos insects insects unidentified chironomid larvae Canada recruits/juv.
zoobenthos insects insects unidentified chironomid pupae Canada recruits/juv.
zooplankton plank. crust. cladocerans unidentified cladocerans Canada recruits/juv.
zoobenthos benth. crust. n.a./other benth. crustaceans unidentified crustaceans Canada juv./adults
zoobenthos benth. crust. n.a./other benth. crustaceans unidentified decapods Canada recruits/juv.
zoobenthos insects insects unidentified dipterans Canada recruits/juv.
zoobenthos insects insects unidentified ephemeropteran nymphs Canada recruits/juv.
nekton finfish bony fish unidentified fish Canada juv./adults
zoobenthos benth. crust. isopods unidentified isopods Canada recruits/juv.
zoobenthos mollusks n.a./other mollusks unidentified mollusks Canada juv./adults
zoobenthos benth. crust. ostracods unidentified ostracods Canada recruits/juv.
zoobenthos insects insects unidentified zygopteran nymphs Canada recruits/juv.
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Yes on crawfish and small BG. PB mag has article on crawfish as a problem for fish recruitment. IIRC there is a study indicating that craws can't do much harm to YP ribbons.

Transactions of the American Fisheries Society 146:173–180, 2017
© American Fisheries Society 2017
ISSN: 0002-8487 print / 1548-8659 online

Predators Reject Yellow Perch Egg Skeins
L. Zoe Almeida
Samuel C. Guffey and Tyler A. Krieg
Tomas O. Höök

Abstract
Despite the high rate of egg mortality due to predation,
few teleost fishes utilize external casings for protecting their
eggs. The gelatinous egg matrix, or skein, produced by Yellow
Perch Perca flavescens may provide a variety of benefits
including deterring egg predators. This study explored the
chemical components of the skein in addition to testing the
preferences of two common egg predators, Round Goby
Neogobius melanostomus and calico crayfish Orconectes
immunis, when presented with three potential egg prey:
Yellow Perch eggs in the skein, Yellow Perch eggs without
the skein, and Fathead Minnow Pimephales promelas eggs.
Preliminary analyses showed that the skein may contain a
variety of potentially noxious components, including piperideine
and the galactose-specific lectin, nattectin. In preference
trials, Yellow Perch eggs in the skein were often approached
first; however, both predators preferred Yellow Perch eggs
with the skein removed and Fathead Minnow eggs rather
than Yellow Perch eggs in the skein. Further experiments
demonstrated that crayfish spent less time attempting to consume
Yellow Perch eggs in the skein after prior exposure to
the skein (day 1: 11.0 min ± 1.3 [mean ± SE]; day 2: 7.6 min ±
1.4), reducing time spent damaging the eggs. These results
indicate that the skein may help protect eggs from predation

In the first experiment,
Round Gobies attempted to consume Yellow Perch eggs
in the skein, but they never succeeded because they rejected
the skein soon after it entered their mouths. After their first
attempt, individual Round Gobies never again put the Yellow
Perch eggs with the skein in their mouths.

The crayfish responses in both experiments indicate that structural
aspects of the skein may deter successful predation. Similar to the Round Goby, crayfish often initially approached and attempted
to consume the Yellow Perch eggs in the skein. Crayfish would
struggle with the skein, attempting to consume the eggs embedded
in the skein. They rarely succeeded, but they also did not have an
immediate rejection response like Round Goby. Because of this,
the Yellow Perch eggs were not consumed, but eggs were
damaged. Many eggs were burst but still embedded within the
skein matrix. After repeated attempts, crayfish reduced the time
spent manipulating the eggs, which may limit long-term losses of
damaged eggs.

Last edited by ewest; 01/13/23 11:42 AM.