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Transcription

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2 ., THE FOOD OF LAKE NPGON FSHES n conjunction with the various studies dealing with the food supply of fish in Lake Nipigon as well as with the studies of the distribution and rates of growth of the fish themselves, examinations of the contents of a considerable number of alimentary tracts of several species of fish have been made. The results, as far as it has been possible to bring them together at the present time, are given in the following tables. n the cases of the larger predaceous fish (lake trout, yellow pike perch, and ling), the numbers in the columns give the actual number of fish eaten and a + sign indicates material disintegrated beyond identification and no attempt made to count individuals. n the tables dealing with the other species an attempt has been made to estimate the percentages of the most abundant organisms found, and the numbers in the tables give these estimates. A + sign in these tables indicates occurrence in amounts not estimated, usually representing less than one per cent. The results of the examination of 455 fish are given, distributed as follows: sturgeon 2, northern sucker 6, common sucker 33, minnows 27, round whitefish 29, common whitefish 65, ciscoes 89, lake trout 42, trout perch 23, small mouth black bass 6, yellow pike perch 2, yellow perch 4, ling

3 74 THE FOOD OF LAKE NPGON FSHES THE FOOD OF LAKE NPGON FSHES 75 NORT HERN SUCKER. Catostomus catostomus.g so STURGEON. Acipenser rubicundus '" <:l. e "<:l... <:l sc. j:; j:; <:l Date Length a, UJ Miscellaneous " t: e "<:l. '" CS '" "'CS.:'".:'" '@. 92 in ern.. '". >. >. ;:l >l, ] e, S No Miscelaneous '" '" h!'l c>!'l c>o. Date Length '".: '" '" ;::. No. 92 in ern. S '" co.<:. > c >.. UJ July Misc. 25 (Bryozoa, Canthocam] t: c>!'l 6 tus, Bosmina longirostri. Camptocercus, Acroperus July ' Misc. 2 (Ephemeridae nymph, Tri choptera larva, Dytiscid larva pae, Alona affinis, A. qua, Chironomidae larvae and pupae rangularis, Cbydorus sphaer Tabanid larva). cus, A lonella nana, A. rostrate Ostracoda, Hyallela knickel June Misc. (Trichoptera larva, Chirono midae larvae, Mollusca, Clad bockerii, Hydracarina, ThJ phora). sanura). July Misc. 4 (Diifiugia, Plumatellc June Pontoporeia hoyi 3; misc. 3 (Hydra carina, Corixa, Trichoptera larva Canthocamptus hiemalis, All and pupa, Coleoptera). na affinis, Chydorus sphaen cus, Ostracoda, Hydracarini June 23 large. ' ' Diatoms). " 23 " 2' Misc. 8 (Pectinatella statoblast, Am phipoda, Odonata nymph, Corixc June , Trichoptera larvae, Chironomida e " Misc.l (B osmina, etc.).,, adult, Nostoc, Ulothrix, Clad, phora, Chara, Bryophyta, highe r plant tissues). " 23 " Misc. 5 (Amphipoda, Trichopter a larvae). " 23 " Cyclops. ' July 9 " Aug. 26 " " 26 " Cladophora. " 26 " 95 4.', '. Cladophora. " 26 " 99 Bosmina longirostris, Diatoms, Ul., + thrix, Cladophora. lephemera simulans. 'Hexagenia bilineata, Ephemera simulans, Heptagenia tripunctata. 'Ephemera simulans. 2 " Diatoms. " Filamentous Algae 6; Diatom s 3; nsecta fragments. July Hyallella knickerbockerii C other forms 5 (Arcella, Cen trop yxis, Cyclops, Ostracode Hydracarina, filamentous A, gae, Diatoms). July June , + July 5?, Misc. 2 (Hydracarina, two Pe coptera nymphs, Chironomida e adult, Diatoms). 2 Misc. Rhizopoda, Cyclop: Cliydorus sphaericus, Ostra coda, Corixa, Ulothrix, Clade phora, Diatoms).

4 76 THE FOOD OF LAKE NPGON FSHES COMMON SUCKER, Catostomus commersonii.s '" & E e No. Date Length OJ OJ OJ Miscellaneous 92. n em. f.!;:;>.l:;;>.l:; "" '" '" '" '" '". ;c! C c \.,jo:l R.,t:: h (,.,) (). <:. June Ostracoda 2; Hydracarina 5; other forms 7 (Cyclops, Canthocamptus, Alona affinis, Chydorus sphaericus, Hyallela knickerbockerii, Diatoms). 2 July Misc. 6 (Canthocamptus, Eurycercus lamellatus, Acroperus harpae, Alona affinis, Chydorus sphaericus, Ostracoda, Hydracarina, Corixa, Ulothrix, Bulbochaete, Diatom s). July Misc. 5 (Centropyxis, Canthocamptus, Alona quadrangularis, Cliydorus sphaericus, Ostracoda, Hydracarina, Diatoms). 5 June Hyallela hnickerbockerii 35; other forms 5 (Cyclops, Callth ocarn p iu s, Plecoptero nymphs, Ephemerido» nymphs, Corixa, Diatoms). July Misc. 4 (Canthocamptus, Bosmina, Eurycercus lamellatus, Alona affinis, Ostracoda, Hydracarina, Corixa, Chirononw: doe pupae, Ulothrix, Diatoms). 8 July app Hydracarilla 4; Ephemeridae nymph (Caenis). 2 Aug Misc. (Hydracorina, Chironomus pupa). THE FOOD OF LAKE NPGON FSHES 77 The stomach contents of a large number of small suckers have been examined. The following list of organisms found in 3 specimens, averaging 2.8 em. in length, taken July 27 in a seine, will illustrate the type of food and the variety of forms found: AlgaeOscillatoria, Melosira, Pinnularia, Navicula, Stauroneis, Amphora, Cocconema, Achnanthes, Surirella, Epithemia, Desmidium, Closterium, Docidium, Staurastrum, Micrasterias, Euastrum, Cosmarium, Oocystis. ProtozoaArcella, Centropyxis, Lecquereusia, Difflugia, cyphoderia, Sphenoderia, Euglypha. RotatoriaKeratella cochlearis, Euchlanis, Lecane luna, Lecane leontina, Lecane sp., Monostyla lunaris, Trichocera, Gastropus stylijer. Oligochaetapodal spines. CopepodaCyclops. Cladoce.raLatona setijera, Daphnia, Bosmina longiros.tris, Eurycercus lamellatus, Kurzia latissima, Acroperus harpae, Alona guttata, A. affinis, Graptoleberis testudinaria, Rynchotalona jalcata, Pleuroxus denticulatus, Chydorus sphaericus, Alonella nana, A. excise, A. exigua, Monospiius dispar. Ostracodaseveral species. Hydracarina nsectaephemeridae nymph, Chironomidae larvae, dipterous pupae. MNNOWS( Cyprinidae) Spottail minnow, Notropis hudsonius Twelve individuals, 5 to 7 em. in length, were taken, on July 2, in a seine close to the dock at the village of Macdiarmid. Bryozoaone statoblast, probably of Pectinatella. Cladoceraa few Bosmina longirostris, Acroperus harpae, Alona sp., many Chydorus sphaericus, a few Polyphemus pediculus. ostracodaf ragmen ts. Arachnidaone watermite and two spiders. nsectaone mayfly nymph, one mayfly subimago, a few Corixa nymphs, several chironomid pupae and adults. MolluscaSnail shell fragments.

5 78 THE FOOD OF LAKE NPGON FSHES Couesius plumbeus Fifteen individuals, 4.2 to 7.4 em. in length, were taken on July 2, in a seine close to the dock at the village of Macdiarmid. Cladoceraconsiderable numbers of Chydorus sphaericus. nsectaone ephemerid or plecopteran nymph, corixids, one beetle, one chironornid larva, one chironomid adult, one Lucillia caesar, several ants. ROUND WHTEFSH. Coregonus quadrilateralis '" <:l.&'" <:l "<:l.. :: :: <:l Date Length '" '" " Miscellaneous "'Q) ;! Q) ;! Q) '"' o: No. 92 in ern. '" :..,. >.. ;:l h (.) (.). 2 Aug. 4 5.D Corixa nymphs ; Ephemeridae nymphs. June M ysis relicta 3; P ontoporeia hoyi ; Corixa 5; other forms (Ostracoda, Hydracarina, small beetle, filamentous Algae). July Chironomidae adults 5; Ostracoda. June " July Aug. 58. app Ostracoda 5; small Homoptera; Algae. 8 " Other forms 3 (Cyclops, Daphnia pulex, Bosmina, Drepanothrix, Alona aifinis, A. quadrangularis, A. costate, Eurycercus lamellatus, Acroperus harpae, Chydorus sphaericus, Ostracoda, Hydracarina, Trichopterc pupa, filamentous Algae, Diatoms). June Ephemeridae nymphs (Ephemerella) 2; Odonata nymph ; Hemiptera. 4 8 THE FOOD OF LAKE NPGON FSHES 79 COMMON WHTEFSH, Coregonus clupeaformis sc <:l e '" <:l '<:l ;! e "<:l "<:l '"... <:l e "<:l e Date Length '" '" " Miscellaneous ;! Q) ;!Q) '" " '"' ".t '" Q) ;::! <:l o: 92 in cm. "': ). :.. >. >.s '"'. ", '" G5. tl., q h Aug Chironomidae adults 5; other forms 5 (Cyclops, Bosmina, longirostris, A croperus harpae, Arachnida, Hemiptera ' Coleoptera, Formicina). July Misc. 4 (Bosmina longirostris Corixa).... " Misc. 5 (Plumatella, A mpbipoda, Plecoptera nymph, Melosira). " app Hemiptera 5; Ephemeridae nymphs (Caenis) 5; Chironomidae adults 2. Aug app M ysis relicta 9; other forms (Diapto, mus, Cyclops, Canthoccmptus, Latona setijera, Bosmina longirostris). June Aug. 56. app Misc. (Hemiptera, dipterous adult). Aug app Bosmina longirostris. July " " u Ephemeridae nymphs (Hexagenia, Caenis) 45; Corixa 5; Trichoptera pupae 5; other forms 5 (Cyclops, Bosmina, nsecta fragments, Cladophora, tu atoms).

6 COMMON WHTEFSHCont., e " <j e <j e "<l "<l.... <j sc <j "'" '" '" Miscellaneous OJ!:: OJ OJ ;:! 92 in cm..g. {; Ol '" Ol, ",,,,. >. >.a h;. :; v'" Vo. No. Date Length s a [uly app.] [july One Leucichthys (cisco) 45; Misc. (Canthocam ptus; Corixa). [june Coleoptera adult, Chironomidae adult. Misc.4 (Mysis relicta, Formicina). [june [One Pygosteus pungitius (ninespined stickleback) and other fish remains 75; other forms 5 (Plumatella, Ephemeridae nymph, Corisa, Cladophora, Diatoms). " Canihocamptus hiemalis, Diaptomus sicilis. [july Algae and higher plants 2. June '3 4 July Ephemeridae nymphs (Heptagenia) [Aug Two Miller's Thumbs and one other fish unident. 98; Eph e meridae nymphs. [june jl:lemiptera 4;. ColeoP: tera 45; Dzptera 4, Formicina 3. [july Misc. (Rotatoria, lDiatoms. Aug Four Pygosteus pungitius (ninespined sticklebacks) and other fish remains Bosmina longirostris, Plecopter nymph, Ephemerdae nymphs (HePtagenia) Cori:JC a, dipterous adult, Diatoms). Jul y 5? Aug. 6? Coleoptera 4. THE FOOD OF LAKE NPGON FSHES 8 CSCOES, Leucichtbys, sc ;:! " e e "<l "<l e. <j ".., <:l ;:! Date Length ". '"!:: '" Miscellaneous OJ!:: OJ '"!:: ;:!. c'. '" N 92 in em, "<l '" oj ;: oj ). ". >.. <:l ""',. o.l o.looo/ v 6:5.. July Misc. (Cyclops, Amphipoda, Hydracarina, Ephemeridce (Ephemerella nymphs, Heptagenic subimago), Corisa, Trichoptera adult, dipterous adult. " Aug Diaptomus ; Cyclops 3; other forms 4 (Daphnia longispina, Bosmina longirostris, Chydorus sphaericus, Hydracarina, dipterous adults). June Misc. 3 (Hydracarina, Formicina). Chalcid, " Misc. 5 (Bryozoa, Hymenoptera, M ollusca, Diatoms). " " July app..... Aug. 46. app Cyclops. June July " Cyclops. " Mollusca. June Ostracoda. July Fragments winged terrestrial insects (Ephemeridae, Hemiptera, Trichoptera, Lepidoptera, Coleoptera, Dip/era, menoptera). June " Aug app Diaptomus. June One small caterpillar. July " June July " app June Hy

7 82 THE FOOD OF LAKE NPGON FSHES LAKE TROUT, Cristovomer namaycusb Nine Date Length spined Trout Miller's Fish No. 92 n em. Ciseoes stiekle perch Thumbs Ling remains backs June 4 2. (6.5 em.) (6.5 cm.) 23. (6.5 em.) 28 3l. 2 + July (6 em.) June (7em.l 4 July 4 5.(?) ( crn.) Aug (37 em.) 2 (23 em.) 2 2 (3 em.) (3 em.) (3 em.) 3 2 (23 em.) + 2 Aug (37em). (42em) THE FOOD OF LAKE NPGON FSHES 83 TROUT PERCH, Percopsis omisco maycus Food of 23 individuals em. in length were taken net set in the Pustagone river. '" '". July 2 in a trap e '" e e <l e "'" "'" "'".,. e.,. c i: i: No. "'". t; <J) c <:> c i:c: Miscellaneous e C OJ ;: OJ ;: OJ " e,, '"'oj C oj C oj ::; i: '"'E. >. > ;.,, o. f.:.lo: (.)oj h (.) Corixidae Cladocera (Ophryoxus gracilis, Chydorus sphaericus) Gyrinid larvae ; Haliplid beetles Algal filaments Dipterous larva Algal filaments; Cladocera (Alona sp.?) Plecoptera nymphs (pupae) Diatoms (Surirella, Navicula) Diatoms (Surirella, Epithemia) A pp Cladocera (Eurycercus lamellatus). Two genera of Ostracoda were represented, namely, Cypria and Candona. Three genera of Ephemeridae were represented, nmely Ephemera, Heptagenia snd Tricorythus. All small dpterous pupae have been considered as Chironomidae, although in some cases the fragmentary state made identification uncertain.

8 84 THE FOOD OF LAKE NPGON FSHES SMALL MOUTH BLACK BASS, Micropterus dolomieu Copepoda Cladocera nsecta ui., sc <::l e c "" <::l 'OJ <::l Date Length '" Epischura '" ec.. ;!." E " t) <::l No. 92 n em. :.:: lacustris <:> <:> '". "" <::l <:i,, o. '}i ;! '" ;! '" c: <::l., ", <:> '"!i E.". >." '". '" '"» d. VJt3 c: '> '>. July " " " YELLOW PKE PERCH, Stizostedion vitreum No. Date Length Ciseoes Ninespined Miller's Fish remain 92 in em. sticklebacks Thumbs Aug July " " " " " " Aug " July " 5 5. (?) (7. Oem.) +. YELLOW PERCH, Perea flauescens Copepoda Cladocera nsecta., " '" ;: <j <::l <::l Date Length t.). en e s:: en <:> <:> <:> o 92 em.. e e ;: t c E Q) c ;! '" ;! '" en t;.s '.s.,.s E' g "'.c <::> No. ; 'i ].!!l ti».<:> '> '.l>4 c:'' G 6 dg Clo.,,,,,,_._._._. AU g June ' ' 7 July ' " 'The Ephemerulae nymphs were Callibaetis sp.? 'The fish were the ninespined stickleback (P'ygosteus pungitius).., f9 THE FOOD OF LAKE NPGON FSHES 85 No. Date Length 92 in em. Jl LNG, Lota moculosa en. '" '" c: ro sc e e u. en en '@..D ",<::l.".". E " c,. ;: <:> <:>.. 'c. c u en t, <:><:> "'!. od l Q) c.". '" Q) Ciscoes ':' ::::::J Q).!< ::J ::Er. c ""'. Z r<.,>'" July " " Aug 'i "" " 8 ".. " " 23 " 2 " " " " " 5 " " " " " " 2 + " " 8 " " 9rne} 3.5 em. " " 4 " " 2{ and} 3 em. " ". 2 " " 2 " " (25 em.) " " 5 " " 5 " " 2 2 " " 3 " ". (3 em.) " " + " ". " ". " " " " 2 3 and} 4 em. " " 4. " ". 2!!!!! 2 " " 3%\ 95% \ + \2%

9 86 THE FOOD OF LAKE NPGON FSHES LNG, Lota maculosa (continued) ",.<:i.5., o c C (,). <:l '@.,..,.. '".,,.<:i.. ;; E E " Ciseoes., :::::::., '" '" No. Date E ;:., (,)., v32 ::E,.<:i. 92., c (,) :::,.<:i.l o '".. Z r ::: in C/) r.., '" '" Aug (23 em.) " ". (2 em.) " ". 2 " ". 5 " ". " ". " ". 3!!! " " 3 " ". 2 + " ". 4 " " " " " " " " " "... + " " " " " " " " " " " " " " " " " "..... % " % 75% % 3% July 4 large. 3 ( em.) Little need be added in amplification of the data given in the tables, but mention may be made of a few outstanding points.. Gill net records show that the northern sucker inhabits deeper water than does the common sucker. The food studies substantiate this fact, in that, as a rule, higher percentages of Pontoporeia occurred in the northern sucker than in the common. t appears also that the older individ., THE FOOD OF LAKE NPGON FSHES 87 uals of the common sucker feed at greater depths than do the younger. 2: Somewhat similar conclusions may be drawn respecting the whitefishes. According to the gill net records, the round whitefish does not extend to as great depths as does the common whitefish, and its food, according to the table, is obtained in comparatively shallow water. The data do not show definitely that the older individuals of the common whitefish feed altogether at greater depths than do the younger. This would be expected where the data is not extensive, because large individuals are often taken in shallow water. t is evident that the common whitefish has serious competitors for food in the suckers, since the latter are bottom feeders and are very abundant in the lake. 3. The ciscoes, although very abundant, come into very little competition with other fish as regards food, in that they are open water plankton feeders, subsisting largely upon Mysis relicta and Limnocalanus. On the other hand they are fed upon extensively by the lake trout. 4. The outstanding item of food of the lake trout is ciscoes. n Lake Nipigon, where the operation of gill nets of 4! inch mesh only is permitted, the number of ciscoes taken is relatively small, and those which are taken are at present sent to the market as whitefish. n view of this fact and since the lake trout is of such great commercial importance, the feeding of the latter upon the ciscoes is not to be deplored. t has been a matter of some surprise that no whitefish have as yet been found in the lake trout stomachs, and if further investigation substantiates this condition, a very fortunate state of affairs will be shown to exist.. 5. The food of the trout perch was evidently obtained n the river. 6. The importance of the ninespined stickleback (Py?osteus pungitius) in the food of the yellow pike perch is nteresting and is possibly correlated with the small numbers of minnows occurring in the lake.. 7. The chief competitor of the lake trout is no doubt the hng, since it apparently feeds largely upon ciscoes. The

10 88 THE FOOD OF LAKE PGO FSHES absence of fish of commercial value in its diet is important. t is interesting to note that five individuals had fed UPon Mysis relicta. The amounts of the latter were so large as to preclude the possibility of their having been contained in cisco stomachs and, in fact, in three cases no other material could be detected. 8. The fish examined fall more or less definitely into the following groups as regards food :() predaceouslake trout, yellow pike perch, ling; (2) bottom feederssturgeon, northern sucker, common sucker, round whitefish, common whitefish; (3) open water plankton feedersciscoes; (4) shallow water plankton and insect feedersyoung common suckers, minnows, young small mouth black bass, young yellow perch; (5) insect feederstrout perch. UNVERSTY OF TORONTO STUDES PUBLCATONS OF THE ONTARO FSHERES RESEARCH LABORATORY No. 7 THE LMNOLOGY OF LAKE NPGON N 922 BY WLBERT A. CLEME S OF l'he DEPARTMENT OF BOLOGY UNVERSTY OF TORONTO TORONTO THE UNVERSTY LBRARY 923