"The invasive rusty crayfish (Orconectes rusticus) and smallmouth bass (Micropterus dolomieu) engage in reciprocal predation during the bass spawning season;. "
It is invasive and more aggressive than most craws. All craws will eat an egg if available and SMB and LMB love craws as a high energy food source.
The effect of craws (density) is a bigger factor on BG and smaller nesting fish who can't eat the craws.
INVASIVE CRAYFISH ORCONECTES RUSTICUS (DECAPODA,CAMBARIDAE) IS A MORE EFFECTIVE PREDATOR OF SUBSTRATENESTING FISH EGGS THAN NATIVE CRAYFISH (O. VIRILIS )
BYJOSHUA W. MORSE, A. K. BALDRIDG and L. W. SARGENT
Oberlin College Department of Biology, Science Center 119 Woodland Street,Oberlin, OH 44047, U.S.A.
Department of Biological Sciences, University of Notre Dame, Galvin Life Sciences Center,Notre Dame, IN 46556,U.S.A.
ABSTRACT Non-indigenous crayﬁsh pose substantial threats to native species, community structure, and ecosystem function in invaded lakes across the globe. The well-documented range expansion of the rusty crayﬁsh Orconectes rusticus is an ideal system to study potential relationships between the attributes that contribute to invasive success, and the ways in which non-indigenous species alterinvaded systems. In Michigan and northern Wisconsin (U.S.A.) lakes whereO. rusticus is replacing its native congener O. virilis it is thought that O. rusticus invasion may account for decreased ﬁshabundance. However, not all of the potential mechanisms that could drive this process have been explored. We examined the hypothesis that O.rusticus are better benthic egg predators than O.virilis,and tested the prediction that O. rusticus would consume substrate bound ﬁsh eggs at a higher rate than its native congener. Support for this hypothesis would suggest that O. rusticus may be able to access a high-energy food source better than O. virilis, and exert predation pressures that could limit the abundance of ﬁsh species which might otherwise limit crayﬁsh populations through top-down control. In laboratory experiments, we determined that O. rusticus exhibit a positive correlation between feeding rate and carapace length not displayed by O. virilis and that larger O. rusticus feed at a higher rate than their native congener. We also found that O. rusticus in laboratory feeding trials engaged in longer feeding events than crayﬁsh foraging in situ in a substrate-spawning ﬁsh nest, a factor which could give O. rusticus an advantage in resource competition with its native congener O. virilis. Collectively, these ﬁndings support the hypothesis that O. rusticus is a better predator of substrate bound ﬁsh eggs than O. virilis, and suggest that direct predation by crayﬁsh may inﬂuence ﬁsh reproduction in lakes where O. rusticus replaces O. virilis