J. Great Res. 29(1):34Ð40 Internat. Assoc. Res., 2003

The Round Goby ( melanostomus) in Pennsylvania Tributary Streams of Erie

Edward C. Phillips*, Meaghan E. Washek, Aaron W. Hertel, and Brian M. Niebel Biology Department Gannon University 109 University Square Erie, Pennsylvania 16541

ABSTRACT. The round goby (Neogobius melanostomus) has successfully colonized the Great Lakes, where it appears to be out-competing and possibly displacing native fish species. Movement of the round goby into tributary streams of Lake Erie could further jeopardize native species. Sampling was done by electrofishing in six Pennsylvania tributary streams of Lake Erie from June 2000 through October 2001. Round gobies were collected from four of the six streams sampled: Elk Creek, Walnut Creek, Twentymile Creek, and Sixteenmile Creek. The most extensive colonization has occurred in Elk Creek where round gobies comprised 17.1% of the total number of fish where they were present, and occurred as far as 2.25 stream km upstream from the mouth of the creek. Round gobies fed almost exclusively on aquatic , and the most important insects in the diet were chironomid larvae. Female round gobies matured at 1+ years old. Individual fecundity ranged from 86 to 591 eggs, and increased with fish length. The plasticity of the diet, high fecundity, and aggressiveness of the round goby may make it a threat to native species in Pennsylvania tributary streams. INDEX WORDS: Round goby, tributary streams, fecundity, age and growth, diet, Lake Erie.

INTRODUCTION 5,000 eggs, depending on the size of the female The round goby (Neogobius melanostomus) is a (Jude 1997, Corkum et al. 1998). Round goby re- recent, and very successful, invader of the Great productive behavior consists of territory establish- Lakes (Jude 2001). Since its introduction, the round ment and defense by males, nest preparation, goby has been one of the most rapidly colonizing courtship, spawning, and paternal care of eggs and invaders of a number of exotic species present in larvae (MacInnis and Corkum 2000). After - the Great Lakes (Mills et al. 1994). They have ing, males aggressively defend the eggs and spread to all five of the Great Lakes from the St. hatched larvae from potential predators (Wickett Clair River, and are very abundant near-shore resi- and Corkum 1998). dents in a number of locations. The round goby is a Additionally, food competition may exist be- benthic species that prefers a cobble substrate, and tween round gobies and native benthic species uses the cover provided by the interstitial spaces in (French and Jude 2001). Round gobies possess rocky areas to avoid predation by piscivorous fish upper and lower molariform pharyngeal teeth, en- (Jude 2001). abling them to crush and feed on bivalve mollusks, The round goby exhibits a number of characteris- which make up the major portion of their diet in tics that have allowed it to be successful in the their native habitats (Skora and Rzeznik 2001, Si- Great Lakes region. Those characteristics include monovicået al. 2001). The abundance of non-native repeat spawning activity within a season, cavity- zebra (Dreissena polymorpha) and quagga (D. bu- nesting behavior, and an aggressive nature. Female gensis) in the Great Lakes, a food resource round gobies can spawn every 20 days and as many that native fish species are unable to effectively ex- as six times per year, and produce from 100 to ploit, is a likely factor contributing to the popula- tion explosion of round gobies (Ghedotti et al. 1995, Ray and Corkum 1997, Weimer and Sowinski *Corresponding author. E-mail: [email protected] 1999). However, round gobies can be opportunistic

34 The Round Goby in Tributary Streams 35

feeders and feed on a variety of invertebrates, fish was being generated during each sampling period. eggs, fish larvae, and adult fish (Carman 2002, After determining the upstream endpoint of round Weimer and Sowinski 1999, Miller 1986), which in- goby colonization the distance in stream km was creases the potential for competition between round measured using the odometer feature of a Garmin gobies and native benthic fish species (French and GPS unit while walking the streambed. The latitude Jude 2001). and longitude of the upstream endpoint was Round goby abundance is well documented in recorded so that future round goby movements the Great Lakes (Jude 2001). However, except for could be assessed. the Detroit, St. Clair, and Flint rivers (Carman Most collected fishes were preserved in a 10% 2002, Jude 2001), little is known about the extent to formalin solution. All gamefish, such as rainbow which round gobies have colonized Great Lakes trout (Oncorhynchus mykiss), brown trout (Salmo tributaries. The primary objective of this study was trutta), and (Micropterus to determine the extent to which round gobies have dolomieui) were released, but the number collected colonized the Pennsylvania tributaries of Lake Erie. was recorded. Preserved fish were returned to the Diets of round gobies were analyzed to determine if laboratory where they were identified to species there is a potential for food competition between and counted. Round gobies were also weighed and round gobies and native species. Additionally, age, measured, and their stomach contents removed for size distribution, and fecundity of round gobies in- diet analysis. Scale samples were taken from each habiting tributary streams were assessed to deter- round goby so that age determinations could be mine how these factors compared with similar made. Fish abundance was calculated for each observations of round gobies in other bodies of species in each stream as catch per unit effort water. (CPUE). Catch per unit effort was calculated as the number of fish captured per hr of electrofishing ef- fort. The relative number of fish of each species in METHODS each stream was also calculated. Sampling by electrofishing was done in six tribu- Fish were measured (total length) to the nearest tary streams of Lake Erie. Twentymile Creek, Six- mm, and weighed to the nearest 0.01g. The length- teenmile Creek, Twelvemile Creek, Walnut Creek, weight relationship for round gobies was calculated Elk Creek, and Conneaut Creek were sampled from using the equation: ln W = a′ + b (ln L). Scales June 2000 through October 2001. All streams were were removed from the area near the tip of the pec- sampled using a battery powered backpack elec- toral fin of each round goby and mounted between troshocker. Sampling was conducted from the two microscope slides. Annuli were counted to de- mouth of each stream (except Conneaut Creek, termine age. where the mouth enters Lake Erie in Ohio) up- Diets were assessed by removing the stomachs of stream until round gobies were no longer encoun- preserved fish. Organisms contained in stomachs tered, and that endpoint was recorded using GPS. were identified and counted. Food items of each Sampling was then continued for at least 0.8 stream taxonomic group were then measured by alcohol km beyond the endpoint to be sure that the endpoint displacement in either a 5-mL graduated cylinder or was correctly identified. Additionally, streams were a 2-mL pipet to determine the volume of each type sampled at sites farther upstream to determine if of food item. Relative numbers (% N), relative vol- there were any disjunct populations of round gob- ume (% V), and the relative frequency (% F) (num- ies, which could have been introduced by bait- ber of fish containing that food item) of food items bucket transfer. The upstream sampling sites were in the stomach of each fish were calculated. From areas with relatively easy access where gobies these data, the index of relative importance (IRI) would most likely be introduced. Upstream sites (Pinkas et al. 1971) for each food item was calcu- where round gobies were not collected were sam- lated for each size group of fish using: IRI = (%N pled for a distance of at least 0.8 stream km. Sam- +%V) % F. Values of IRI can range from 0 to pling time at each site in each stream was variable 20,000, with higher values representing food items because of variation in stream size. Streams were of greater importance. Fish were divided into four sampled in an upstream direction by making a size classes (< 45 mm, 45 to 59 mm, 60 to 74 mm, crossing pattern in each stream to cover the water ≥ 76 mm) to determine if diet changed with fish as efficiently as possible. The electroshocker size. Fish with empty stomachs were excluded from recorded the time (in seconds) that electric current the analysis. 36 Phillips et al.

TABLE 1. Catch per hr (CPUE) and relative abundance (% of total number collected) of fish elec- troshocked from Pennsylvania tributary streams of Lake Erie, 2000 and 2001. Common names assigned according to Robins et al. (1991). 20mile Walnut 16mile Conneaut 12mile Elk Creek Creek Creek Creek Creek Creek Common Name CPUE % CPUE % CPUE % CPUE % CPUE % CPUE % Round Goby 137.1 17.1 103.8 30.4 42.6 12.7 13.7 1.5 Rainbow Darter 238.1 29.6 94.3 27.7 47.5 14.2 90.6 9.2 163.0 25.7 Fantail Darter 16.2 2.0 28.3 8.3 8.2 2.4 100.0 10.1 88.9 14.1 Johnny Darter 1.9 0.2 8.6 1.1 8.3 2.4 18.2 5.4 610.3 68.3 3.1 0.3 Greenside Darter 206.3 20.8 Mottled 3.8 0.5 1.2 0.3 0.8 0.3 57.8 9.0 Northern Hog Sucker 10.5 1.3 3.5 1.0 3.3 1.0 Rainbow Trout 11.4 1.4 23.6 6.9 5.7 1.7 68.6 7.7 69.1 10.9 Brown Trout 1.0 0.1 Bluegill 6.7 0.8 11.5 3.4 Pumpkinseed 2.9 0.3 Rock Bass 2.9 0.3 4.1 1.2 118.8 12.0 1.2 0.2 1.2 0.2 Smallmouth Bass 9.5 1.2 36.6 4.1 Sea Lamprey 1.6 0.5 Stonecat 1.0 0.1 2.5 0.7 6.3 0.6 Yellow Bullhead 0.8 0.3 Brown Bullhead 12.4 2.0 Minnows 352.4 43.7 77.8 22.9 188.4 56.25 146.3 18.4 465.6 47.0 240.7 37.9 Total hr fished 6.1 5.6 5.3 2.2 2.1 2.6 Total fish collected 1,227 771 842 606 517 513

Fecundity was determined by removing the bedrock, where they occupied horizontal ledges in ovaries from gravid females, and then counting the the bedrock. eggs. The relationship between fish length and The second greatest catch of round gobies oc- number of eggs was analyzed using simple linear curred from Twentymile Creek, where 104 round regression: ln number of eggs = a′ + b (ln L). gobies were collected per hour of electrofishing. In Twentymile Creek round gobies made up 30.4% of RESULTS fish collected, where round gobies occurred. Round Round gobies were collected from four of the six gobies occurred 0.64 stream km upstream from the mouth of Twentymile Creek (N42¡15.571′ and streams sampled (Table 1). Catch per hr of round ′ gobies was greatest in Elk Creek where 137 round W079¡46.635 ). Round gobies were collected pri- gobies were collected per hr of electrofishing. marily from stream areas with moderate flow and a Where present, round gobies made up 17.1% of the gravel/rock substrate. fish present in Elk Creek. Round gobies were col- The third greatest catch of round gobies occurred lected as far as 2.25 stream km upstream from the from Walnut Creek where 43 round gobies were mouth of Elk Creek (N42¡01.229′ and collected per hour of electrofishing. Round gobies W080¡21.683′). Although no quantitative data were made up 12.7% of fish collected where round gob- collected about which areas of Elk Creek were most ies occurred. Round gobies were collected as far as heavily colonized, round gobies were collected 0.48 stream km upstream from the mouth of Walnut from all stream habitats. They appeared to be most Creek (N42¡04.421′ and W080¡14.075′). Round abundant in areas with moderate flow, which con- gobies were collected primarily from areas with tained gravel and larger rocks. However, round go- moderate flow and a gravel/rock substrate. bies were also collected from shallow riffle areas Round gobies were also collected from Sixteen- containing primarily gravel and from areas of mile Creek at a rate of 14 round gobies per hour of The Round Goby in Tributary Streams 37

TABLE 2. Diets of round gobies collected from four Pennsylvania Lake Erie tributaries during 2000 and 2001. Diet is shown for four size classes. % F = the percentage of fish containing that food item, % N = % composition by number, %V = % composition by volume, IRI = index of relative importance = (% N + % V) % F. Some columns of % N and % V do not add to 100% because of rounding error. 30Ð44 mm (N = 72) 45Ð59 mm (N = 123) 60Ð74 mm (N = 76) ≥ 75 mm (N = 49) Food Item %F %N %V IRI %F %N %V IRI %F %N %V IRI %F %N %V IRI Diptera Chironomidae 94 84 64 13,912 92 84 56 12,880 78 83 53 10,608 78 63 40 8,034 Ephemeroptera Caenidae 31 8 21 899 32 7 19 832 38 5 17 836 65 14 15 1,885 Baetidae 15 2 9 165 14 1 4 70 22 2 4 132 Heptageniidae 5 1 4 25 16 2 11 208 55 11 31 2,310 Trichoptera Hydropsychidae 9 2 9 99 7 1 5 42 14 1 7 112 55 4 4 440 Hydroptilidae 6 3 3 54 17 4 3 119 22 4 3 154 Limnephilidae 22 3 3 132 Plecoptera Perlidae 20 1 2 60 Other 12 3 3 33 16 2 5 16 25 5 6 42 22 2 1 66

electrofishing. Round gobies only made up 1.5% of served is described by the equation: lnW = -11.632 fish collected in Sixteenmile Creek. Round goby + 3.095 (lnL). catch was low because fish were collected only Round goby diets were analyzed based on four from a pool a few meters above the mouth. There- size classes (N = 329 fish, 9 empty) and fish of all fore no GPS coordinates were recorded for round size classes fed almost exclusively on benthic goby movement into Sixteenmile Creek. macroinvertebrates, primarily aquatic insects (Table Round gobies were not collected from 2). In general, chironomid larvae and pupae (data Twelvemile Creek or Conneaut Creek. Additionally, combined) were the most important food items for no disjunct populations of round gobies were col- all four size classes, but round gobies > 75 mm relied lected in upstream areas of any of the sampled less heavily on chironomids than round gobies in the streams. In addition to the fish listed in Table 1, the smaller size classes. Round gobies < 45 mm fed pri- minnows (Cyprinidae) most commonly collected marily on chironomids (IRI = 13,912), and had the during this study were: river chub (Nocomis micro- narrowest diet breadth of the size classes with only pogon), central stoneroller (Campostoma seven different food items found. Round gobies in the size class 45 to 59 mm also fed most heavily on anomalum), common shiner (Notropis cornutus), chironomids (IRI = 12,880), but had a wider diet sand shiner (Notropis stramineus), mimic shiner breadth feeding on 12 different food items. Round (Notropis volucellus), longnose dace (Rhinichthys gobies in the size class 60 to 74 mm again had simi- cataractae), blacknose dace (Rhinichthys atratu- lar diets, feeding mainly on chironomids (IRI = lus), and bluntnose minnow (Pimephales notatus). 10,608). Round gobies in this size class had the Round goby total length ranged from 22 to 112 greatest diet breadth feeding on 13 different food mm, and weight ranged from 0.15 to 17.58 g. Based items. Fish in the fourth size class, > 75 mm, also fed on aging fish by counting scale annuli, four age mainly on chironomids (IRI = 8,034) but had a more groups were collected: 0+, 1+, 2+, and 3+. Age balanced diet, based on IRI, than fish from smaller groups had considerable length overlap, but the size classes. Fish in this size class also fed relatively mean length (± SE) of each group was: 0+: 44.2 heavily on Heptageniidae and Caenidae. Other prey mm (± 1.7), 1+: 67.9 mm (± 1.9), 2+: 79.8 mm (± items in the diets of round gobies not listed in Table 3.2), and 3+: 93.5 mm (± 5.1). All four age 3+ fish 2 included Tipulidae, Elmidae, Ptilodactylidae, were females. Fish in the other size groups were Psephenidae, and Dytiscidae larvae, Formicidae comprised of both males and females. The length- adults, water mites, and fish eggs. No adult or larval weigh relationship (r2 = 0.980, P < 0.0001) ob- fish were found in any stomachs. 38 Phillips et al.

Female round gobies became mature at 1+ years current locations will allow the monitoring of future old. The mean length of gravid females was 66 mm round goby movements. (range 54 to 112 mm). Mean fecundity was 177 The plasticity of the round goby diet may be a (range 86 to 591 eggs). The relationship (r2 = 0.87, factor in its successful colonization of the Great P < 0.0001) between length and fecundity is ex- Lakes region. Round gobies generally prefer to feed plained by the equation: ln number of eggs = -6.06 on mollusks (primarily zebra mussels) where they + 2.79 (lnL) (where L = total length in mm). are available (Ghedotti et al. 1995, Ray and Corkum 1997, Weimer and Sowinski 1999, Si- DISCUSSION monovic et al. 2001, Skora and Rzeznik 2001). However, in a study of the St. Clair River, Michi- While round gobies made up a substantial pro- gan, French and Jude (2001) found that round gob- portion of the fish collected (30.4% in Twentymile ies fed mainly on zebra mussels in deep water, but Creek, 17.1% in Elk Creek, 12.7% in Walnut fed on other macroinvertebrates in shallower water. Creek) in Pennsylvania tributary streams, Carman In this study, along with other studies conducted in (2002) found that they made up 79% of the fish col- waters that do not contain zebra mussels (Carman lected from the Flint River, Michigan. The differ- 2002), round gobies were found to readily change ence in round goby composition between the two their diets to include primarily non-mollusk benthic areas could be a result of greater overall fish diver- invertebrates. In the Flint River, Michigan, Carman sity in the Pennsylvania tributaries, and/or less (2002) found that round gobies fed primarily on human impact on the Pennsylvania tributaries. chironomid larvae, which is very similar to the Elk Creek is the largest of the tributary streams findings in this study in Pennsylvania tributary studied and it contains few physical obstacles to streams. Round goby diets from Pennsylvania tribu- colonization. Therefore it is currently the stream tary streams of Lake Erie, however, were very dif- most likely to be colonized farther upstream by ferent from the diets of round gobies collected from round gobies. General habitat preference of round Lake Erie. Weimer and Sowinski (1999) found that gobies was relatively similar in each Pennsylvania round gobies in Lake Erie fed predominantly on tributary stream, with round gobies preferring rocky zebra mussels and zooplankton, with larger fish re- areas with moderate flow. However, unlike in Elk lying more heavily on zebra mussels and smaller Creek, round gobies were rarely collected from fish relying more heavily on zooplankton. In the areas of bedrock in Walnut Creek or Twentymile tributary streams sampled in this study all size Creek, possibly because the bedrock areas in those classes of round gobies fed most heavily on chi- streams were much shallower and contained fewer ronomids and almost exclusively on non-mollusk ledges than bedrock areas in Elk Creek. These shal- benthic macroinvertebrates; whereas, in Lake Erie low bedrock areas may be acting as a physical bar- only approximately 30% of round gobies fed on rier to the movement of round gobies farther chironomids (Weimer and Sowinski 1999). upstream in Twentymile and Walnut Creeks. Far- Round goby fecundity was previously studied in ther progression of gobies in Twentymile Creek ap- the Detroit River by MacInnis and Corkum (2000), pears to also be blocked by two small water falls. and results from that study were very similar to our Round goby abundance is relatively high directly findings in Pennsylvania tributary streams. In both below the water falls and no round gobies were col- areas, females were mature at 1 year old, which dif- lected above the water falls. fers from European populations of round gobies Round gobies were not collected from which mature at 2 to 3 years old (Miller 1984, Twelvemile Creek or the Pennsylvania reaches of Miller 1986). The length of gravid females from the Conneaut Creek. However, round gobies have been Detroit River ranged from 42 to 92 mm (standard collected from the lower reaches of Conneaut length) (mean = 60 mm) which is similar to the Creek, Ohio (D. Jude, personal communication, findings in this study of a range of 54 to 112 mm University of Michigan, Ann Arbor, MI). No dis- (total length) (mean = 66 mm). Individual fecundity junct populations of round gobies were found in in the Detroit River ranged from 84 to 606 eggs, any upstream reaches of the tributary streams, and in Pennsylvania tributary streams it ranged which indicates that thus far no round gobies have from 86 to 591 eggs. been introduced by “bait-bucket transfer.” It is pos- Although this study did not focus directly on sible that further progression will occur into Penn- round goby spawning in tributary streams there is sylvania tributary streams over time, and the evidence that spawning is occurring there. A num- The Round Goby in Tributary Streams 39 ber of males that showed spawning/nest guarding REFERENCES colors were collected from Elk Creek, Twentymile Carman, S. 2002. Temporal feeding variation in riverine Creek, and Walnut Creek. This, coupled with the round gobies. M.S. thesis, Loyola University, Chicago collection of a relatively large number of gravid fe- IL. males in the streams, indicates that round gobies are Charlebois, P.M., Marsden, J.E., Goettal, R.G., Wolfe, probably spawning there. This could lead to a much R.K., Jude, D.J., and Rudnicka, S. 1997. The round more dramatic colonization of tributary streams in goby Neogobius melanostomus (Pallus): a review of the future, because much of the colonization suc- European and North American literature. Illinois- Indiana Sea Grant Program and Illinois Natural His- cess of round gobies has been attributed to their tory Survey. INHS Special Publication No. 20. ability to spawn multiple times per year. MacInnis Corkum, L.D., MacInnis, A.J., and Wickett, R.G. 1998. and Corkum (2000) estimated that females spawn Reproductive habits of round gobies. Great Lakes three times per year in the Detroit River, and that Res. Rev. 3:13Ð20. absolute individual fecundity ranges from 252 to Dubs, D.O.L., and Corkum, L.D. 1996. Behavioral inter- 1,818 eggs per round goby female. Similar annual actions between round gobies (Neogobius melanosto- fecundity, coupled with fertilization and hatching mus) and mottled (Cottus bairdi). J. Great rates as high as 95% (Charlebois et al. 1997) could Lakes Res. 22:838Ð844. produce dramatic increases in round goby density French, J.R.P. III, and Jude, D.J. 2001. Diets and diet overlap of nonindigenous gobies and small benthic in Pennsylvania tributary streams. native fishes co-inhabiting the St. Clair River, Michi- The aggressiveness of the round goby may allow gan. J. Great Lakes Res. 27:300Ð311. it to displace less aggressive native species, such as Ghedotti, M.J., Simhula, J.C., and Smith, G.R. 1995. the mottled sculpin (Cottus bairdi), that have simi- Zebra predation by round gobies in the labora- lar habitat requirements (Hoekstra and Janssen tory. J. Great Lakes Res. 21:665Ð669. 1985, Jude et al. 1995, Dubs and Corkum 1996, Hoekstra, D.M., and Janssen, J. 1985. Non-visual feed- Janssen and Jude 2001). Dubs and Corkum (1996) ing behavior of the mottled sculpin in Lake Michigan. found that round gobies aggressively drove mottled Environ. Biol. Fish. 12:111Ð117. sculpins from their shelters. Round gobies also in- Janssen, J., and Jude, D.J. 2001. Recruitment failure of mottled sculpin Cottus bairdi in Calumet Harbor, terfere with nest-guarding male mottled sculpins southern Lake Michigan, induced by the newly intro- which exposes the nest to egg predation, which was duced round goby Neogobius melanostomus. J. Great the case in Calumet Harbor, where mottled sculpin Lakes Res. 27:319Ð328. recruitment failure contributed to dominance by Jude, D.J. 1997. Round gobies: cyberfish of the third round gobies (Janssen and Jude 2001). In Lake Erie millennium. Great Lakes Res. Rev. 3:27Ð34. tributary streams it was found that mottled sculpins ——— . 2001. Round and tubenose gobies:10 years with were absent from, or had very low densities in, the latest Great Lakes phantom menace. Dreissena streams invaded by round gobies (Elk Creek, Wal- 11:1Ð14. nut Creek, Twentymile Creek). However, in ——— , Janssen, J., and Crawford, G. 1995. Ecology, dis- tribution, and impact of the newly introduced round Twelvemile Creek, which contained no round gob- and tubenose gobies on the biota of the Detroit and St. ies and had good mottled sculpin habitat, relatively Clair Rivers. In The Lake Huron ecosystem: ecology, high numbers of mottled sculpins were collected. fisheries, and management, eds. M. Munawar, T. These data suggest that round gobies may be dis- Edsall, and J. Leach., pp. 447Ð460. Ecovision World placing mottled sculpins in tributary streams. How- Monograph Series, S.P.B. Academic Publishing, The ever, there are no background data describing Netherlands. sculpin densities and distributions prior to the round MacInnis, A.J., and Corkum, L.D. 2000. Fecundity and goby invasion. Further monitoring of streams such reproductive season of the round goby Neogobius as Twelvemile Creek may provide insight into in- melanostomus in the upper Detroit River. Trans. Am. Fish. Soc. 129:136Ð144. teractions between round gobies and mottled Miller, P.J. 1984. The tokology of gobioid fishes. In Fish sculpins in Great Lake tributary streams. reproductive strategies and tactics, eds. G.W. Potts and R.J. Wooten., pp. 119Ð153. London: Academic ACKNOWLEDGMENTS Press. ——— . 1986. . In Fishes of the Northeastern We thank the Pennsylvania Sea Grant and Gan- Atlantic and the Mediterranean, eds. P.J.P. White- non University for grants, which supported this re- head, M.L. Bauchot, J.C. Hureau, J. Neilson, and E. search. Tortonese., pp. 1019Ð1085. UNESCO, Paris. 40 Phillips et al.

Mills, E.L., Leach, J.H., Carlton, J.T., and Secor, C.L. River basin, Yugoslavia. J. Great Lakes Res. 1994. Exotic species and the integrity of the Great 27:281Ð289. Lakes. Bioscience 44:666Ð667. Skora, K.E., and Rzeznik, J. 2001. Observations on diet Pinkas, L., Oliphant, M.S., and Iverson, I.L.K. 1971. Food composition of Neogobius melanostomus Pallas 1811 habits of albacore, bluefin tuna, and bonito in Califor- (Gobiidae, Pisces) in the Gulf of Gdansk (). nia waters. Calif. Dep. Fish Game Fish Bull. 152. J. Great Lakes Res. 27:290Ð299. Ray, W.J., and Corkum, L.D. 1997. Predation of zebra Weimer, M., and Sowinski, M. 1999. Diet of the round mussels by round gobies, Neogobius melanostomus. goby (Neogobius melanostomus) in Lake Erie. Dreis- Environ. Biol. Fish. 50:267Ð273. sena 10:7Ð12. Robins, C.R., Bailey, R.M., Bond, C.E., Brooker, J.R., Wickett, R., and Corkum, L.D. 1998. Nest defense by Lachner, E.A., Lea, R.N., and Scott, W.B. 1991. the non-indigenous fish, the round goby, Neogobius Common and scientific names of fishes from the melanostomus (Gobiidae), on a shipwreck in western United States and Canada. 5th ed. Amer. Fish. Soc. Lake Erie. Can. Field-Naturalist 112:653Ð656. Spec. Publ. 20:1Ð183. Simonovicå, P., Paunovicå, M,. and Popovicå, S. 2001. Submitted: 9 February 2002 Morphology, feeding, and reproduction of the round Accepted: 18 September 2002 goby, Neogobius melanostomus (Pallus), in the Editorial handling: John Janssen