1 9 6 5 Yellow Perch Predation on Bythotrephes cederstroemi in Little Bay de Noc and Big Bay de Noc, Lake Michigan, 1988 Philip J. Schneeberger Fisheries Research Report No. 1965 December 20, 1989 MICHIGAN DEPARTMENT OF NATURAL RESOURCES FISHERIES DIVISION Fisheries Research Report No. 1965 December 20, 1989 YELLOW PERCH PREDATION ON BYTHOTREPHES CEDERSTROEMI IN LITTLE BAY DE NOC AND BIG BAY DE NOC, I.AKE MICHIGAN, 1988 Philip J. Schneeberger 1 A contribution from Dingell-Johnson Project F-53-R, Michigan. Michigan Department of Natural Resources Fisheries Research Reporl No. 1965, 1989 Yellow Perch Predation on Bythotrephes cederstroemi in Little Bay de Noc and Big Bay de Noc, Lake Michigan, 1988 Philip J. Schneeberger Michigan Department of Natural Resources Marquette Fisheries Research Station 488 Cherry Creek Road Marquette, Michigan 49855 Abstract.--Stomach contents were examined from 1,164 yellow perch (Percajlavescens) collected from Little Bay de Noc and Big Bay de Noc, Lake Michigan, June through October, 1988. Diet through August consisted of several different taxa considered typical for yellow perch. During September and October, 124 perch (76 to 213 mm total length) contained 1-120 (mean = 16.7) of the exotic cladoceran Bythotrephes cederstroemi. Of 39 other fish species examined, only rock bass (Amb/oplites rupestris) was found to have ingested Bythotrephes. Trout-perch (Percopsis omiscomaycus) had considerable dietary overlap with yellow perch, but no trout-perch was found to have eaten B. cederstroemi. The overall proportion of yellow perch preying on B. cederstroemi was higher in Little Bay de Noc (32%) than in Big Bay de Noc (4%). Within individual fall net samples, from O to 72% of the yellow perch contained Bythotrephes. Yellow perch appeared to prefer B. cederstroemi (when available) over other food items that had comprised their diet earlier in the year and continued to be available during the fall. Many age-0 yellow perch were large enough by September to consume Bythotrephes, but 1- to 4-year-old fish may have been more efficient in handling the cladoceran. If B. cederstroemi become abundant prior to September in subsequent years, age-0 perch may not be of sufficient size to prey on them. Bythotrephes cederstroemi is a predaceous by 1987 (B. Belonger, personal cladoceran which recently invaded and spread communication, Wisconsin Department of throughout all of the Great Lakes. Natural Resources, Marinette, Wisconsin) but Previously restricted to a northern and prior to this report were not known to central Palearctic distribution (Lehman 1987), inhabit northern Green Bay. Evans (1988) B. cederstroemi was reported first in Lake hypothesized that the apparent ease with Huron in 1984 (Bur et al. 1986); which B. cederstroemi became established in documentation of its presence in the other the Great Lakes may relate in part to Great Lakes was complete within 3 year (Bur reduced predation on the near-surface et al. 1986, Lange and Cap 1986, Lehman plankton community as alewife (Alosa 1987, Cullis and Johnson 1988). B. pseudoharengus) have become relatively less cederstroemi are known to have invaded abundant in the 1980s (Jude and Tesar 1985, southern Green Bay, Lake Michigan, at least Hartman 1988). 1 B. cederstroemi typically hatch in spring length) sampled from Lake Michigan in and increase parthenogenetically as October 1986 had an average of 3.7 (range iteroparous females during the summer. 1-15) B. cederstroemi in their stomachs (Evans Each female is capable of producing several 1988), quantitative ingestion rates of B. broods. In the fall B. cederstroemi switch to cederstroemi by fish either in Europe or the gametogenic reproduction to produce resting Great Lakes are lacking. This study gives eggs, which lay dormant through the winter seasonal, quantitative, and size-related (Evans 1988, Lehman 1988). information on yellow perch predation on B. B. cederstroemi are voracious predators. cederstroemi in northern Green Bay. In Lake Michigan, the main prey items during the summer are herbivorous Cladocera, including dominant grazers Methods (Lehman 1987). The potential for Bythotrephes to reduce zooplankton Field work was performed in the assemblages could affect fish communities, Michigan waters of Green Bay in Little Bay because many small and young-of-the-year de Noc and Big Bay de Noc (Figure 1). Fish fish rely on this grazing community for food were collected each month from June (Lehman 1987, Barnhisel in review). There through October, 1988. Trawls, experimental is concern that these fish may not be able to gill nets, and seines were used in water 0.3- switch to eating B. cederstroemi because to 16.7 m deep in an attempt to capture all Bythotrephes have terminal spines that species and sizes of fish. Trawl haul duration typically exceed individual body lengths by was 10 min; gill net sets were 24 hours; seine threefold (Barnhisel in review). Caudal haul distance was 20 to 30 m. Fish were spines may affect B. cederstroemi buoyancy measured and examined in the field or whole (Zozulya and Mordukhai-Boltovskoi 1977) but specimens were preserved in 10% formalin may also serve as deterrents to potential for examination in the lab. predators (Evans 1988, Barnhisel in review). Stomachs from 1,164 yellow perch (64 B. cederstroemi are readily ingested by to 297 mm total length) and 606 stomachs many juvenile and adult fish. In northern from 39 other species were examined. Europe, B. cederstroemi are important in the Twenty-five fairly general stomach content diets of several fish species (Lindstrom 1955, categories were differentiated and empty Berg and Grimaldi 1966, Nilsson and Pejler stomachs were also recorded. Food items 1973, Nilsson 1979). In the Great Lakes, B. were enumerated for each stomach and cederstroemi have been found in the stomachs summaries were generated to allow of yellow perch (Perea flavescens), white examination of diet by species, season, bay, perch (Morone americana ), white bass (M and size of fish. Other summaries listed chrysops ), walleye (Stizostedion vitreum) (Bur combinations of multiple food items in et al. 1986), deepwater sculpin individual stomachs. (Myoxocephalus thompsoni) (Evans 1988), chinook salmon ( Oncorhynchus tshawytscha ), pink salmon (0. gorbuscha) ( Cullis and Results Johnson 1988), lake trout (Salvelinus namaycush) (R. Schorfhaar, personal Most ( 66%) of the yellow perch communication, Michigan Department of examined in this study were captured by trawl Natural Resources, Marquette, Michigan), (Table 1). Of the others, approximately 21 % rock bass (Ambloplites rupestris) (this report) were caught in gill nets and 12% in seines. and alewife (Schneeberger, unpublished data). Trawls and seines tended to catch smaller Aside from the report that 9 of 10 perch while gill nets caught the largest deepwater sculpin (24 to 153 mm total specimens. 2 Yellow perch consumed several taxa, items that both species had been preying most of which were eaten throughout the upon earlier in the year (Table 4). No study period by a wide size range of fish trout-perch (N = 295; mean TL = 87 mm; (Table 2). B. cederstroemi was a new food length range = 30-137 mm) was found item, which appeared in perch stomachs in containing B. cederstroemi. September and October. B. cederstroemi Consumption of B. cederstroemi were numerically more abundant in yellow occurred in both bays during September and perch stomachs than any other food item October, but the overall percentage of yellow even though Bythotrephes were consumed perch preying on Bythotrephes was much only during the last 2 months of sampling higher in Little Bay de Noc (32%) than in while other top food items were ingested Big Bay de Noc (4%). Frequencies of throughout the study period (Table 2). occurrence of food items other than B. Yellow perch between 76 and 213 mm total cederstroemi were also different for yellow length were found to have ingested B. perch in each bay (Table 5), but perch cederstroemi. Individual fish consumed from length-at-age was not significantly different 1 to 120 (mean = 16.7) Bythotrephes (Table between bays (Table 6). Within individual 2). net samples collected during September and Overall, 28% of the yellow perch that October, the proportion of yellow perch ate B. cederstroemi were under 100 mm and eating B. cederstroemi ranged from 18 to 72% 89% were smaller than 140 mm (Table 3). in Little Bay de Noc and from O to 19% in A regression of fish length on the number Big Bay de Noc. of Bythotrephes consumed was not significant (r = 0.06), but the mean number of Discussion Bythotrephes ingested by perch larger than 99 mm total length (20.8) was significantly larger Diet information collected in this study (P<0.05) than the mean for smaller fish was coherent despite the combining of data (6.4). Of the fish that had eaten B. from three different types of sampling gear. cederstroemi, most (79%) contained no other Hayward et al. (1989) demonstrated that food item in their stomachs while 21 % had point estimates of food consumption by eaten one or two other food types along with yellow perch were biased when fish were Bythotrephes. Seven yellow perch which had caught in gill nets because passive gear eaten B. cederstroemi were found to have tended to collect the most active fish that considerable masses of tangled spines in their were more likely to have been feeding; trawls intestines. Intestinal perforations were not were better at collecting the full spectrum of observed. active and quiescent fish. Diet studies of fish Although 39 species besides yellow caught in gill nets are also confounded perch were caught during the course of this because digestion of food progresses during study, only 15 were collected during the the time of capture (Eggers 1977). September-October period. Of these, rock Seventy-nine percent of the yellow perch bass was the only other species found to have stomach data in the present study came from eaten B.