Evidence of Natural Reproduction by Planted Lake Trout in Lake Michigan

J. Great Lakes Res. 7(1):57-61 Internat. Assoc. Great Lakes Res. 1981

NOTE EVIDENCE OF NATURAL REPRODUCTION BY PLANTED LAKE TROUT IN LAKE MICHIGAN

David J. Jude, Sharon A. Klinger, and Michael D. Enk Great Lakes Research Division Institute of Science and Technology University of Michigan Ann Arbor, MI48109

ABSTRACT. Lake trout (Salvelinus namaycush)fry were captured in southeastern Lake Michiganfor the first time since the species was reintroduced from hatchery stocks in 1965. Spawning apparently occurred infa1l1979 on newly placed limestone riprap covering recently constructedpowerplant intake and discharge pipelines. Eggs presumably hatched in late February-March, 1980, and57fry (22-43 mm total length) were collected April-June, 1980, and three fry (55-62 mm) were collected in August, 1980.

monitoring samples have been far too low to indicate significant natural reproduction. In our studies from 1973 to 1980 (unpublished data, Great Lakes Research Division) less than 3% of the lake trout collected were unclipped, while lake trout collected in fall, 1980, near Saugatuck and Port Washington by the V.S. Fish and Wildlife Service exhibited a 1.6% unclipped rate (unpublished data, Great Lakes Fishery Laboratory, Ann Arbor, MI). Most unclipped trout are still thought to be of hatchery origin; they were either unclipped at the hatchery or clips were regenerated and subsequently overlooked when fish were examined.

INTRODUCTION Historically, lake trout (Salvelinus namaycush) was one of the most valuable commercial species in the upper Great Lakes (Smith 1968). Sea lamprey predation and overfishing are thought to have virtually eliminated native lake trout from Lake Michigan by the early 1950s (Van Oosten 1946; Smith 1968, 1972; Christie 1974). By the early 1960s, efforts coordinated by the Great Lakes Fishery Commission brought sea lamprey populations under control (Crowe 1975) and commercial fishing for lake trout was banned in Lake Michigan (State of Michigan 1966). Since 1965, over 34 million fin-clipped lake trout yearlings (about 2 million annually) have been stocked in Lake Michigan in an effort to reestablish self-sustaining populations (Peck 1979; A. Ballert, personal communication, Great Lakes Commission, Ann Arbor, MI). No lake trout fry have ever been collected, except in Grand Traverse Bay (Figure 1) (Stauffer 1978a, 1979b; Wagner 1980), despite the fact that mature lake trout in spawning and postspawning condition have been captured over known spawning reefs (Peck 1979), that eggs have been collected from these reefs (Peck 1979), and that eggs collected from reefs and directly from Lake Michigan lake trout have successfully hatched (Stauffer 1979a; J. Dorr, personal communication, Great Lakes Research Division, V niversity of Michigan, Ann Arbor, MI). The incidental occurrences of unclipped juvenile and adult lake trout in lakewide assessment and power plant

MATERIALS AND METHODS All sampling occurred near the J. H. Campbell Power Plant, southeastern Lake Michigan, near Port Sheldon, Michigan (Figure 1) where new offshore intake and discharge pipelines were built. Approximately 1296 m of pipeline was covered with 10- to 20-cm diameter crushed limestone, 594 m of which was overlaid with an incomplete layer of 1.2to 1.5-m diameter, 900-kg limestone boulders. An additional length of 360 m had a complete 1.5-m layer of large riprap covering a base of crushed limestone. Width of the rock covering ranged from 8 to 68 m. Rocky substrate was therefore available at all depth contours from shore to 11 m. Sampling was performed during day and night once per month, April through November, along two transects extending perpendicularly from shore, one in the immediate vicinity of the plant (north

57

58

JUDE, KLINGER, and ENK

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I

,"

t I N

\

( c« ,

I

o

Meters I I 400 800

I 1200

I (\ (

Wis.

III.

E

!!?

Benton Harbor St. Joseph

E

~

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en

EE

CD C\I

( . C. Cook Plant) Mich.

Ind.

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6000

FIG. 1. Map ofLake Michigan with inset showing study area, location of transects, riprap area(---- =10- t020-cm diameter crushed limestone, = 1.2- to 1.5-m boulders), and stations where one or more lake trout fry were captured ( .... ), April-August 1980.

transect) and the other located 3.1 km south (south transect). A larval fish sled (Yocum and Tesar 1980) equipped with a 0.363-mm mesh plankton net was towed along the bottom at 1-, 1.5-,3-,6-,9-,12-, and 15-m depth contours at both transects; bottom trawling for juvenile and adult fish was performed at depths of 3,6,9, 12, and 15 m at the south transect, and at 6 and 9 m at the north transect. The trawl was a semi-balloon, nylon otter trawl with a 4.9-m headrope and a 5.8-m footrope. The body, cod end,

and cod end innerliner of the net were composed of 1.9-, 1.6-, and 0.63-cm bar mesh, respectively. RESULTS AND DISCUSSION Lake trout fry (two fish, 26 and 27 mm total length) were first collected on 21 April, 1980, by the larval fish sled in 12 and 15 m of water in the area of new riprap at the north transect (Table 1). During 19-22 May, 1980, lake trout fry were widely dispersed, being collected by trawl (47 fish, 22-35 mm) and sled

59

NOTE-LAKE TROUT REPRODUCTION IN LAKE MICHIGAN

TABLE 1. Date, location, and total length ranges for lake trout fry collected during 1980 in Lake Michigan near Port Sheldon, Michigan.

Date 21 Apr 19-22 May

Gear Sled Trawl

Transect North North

Sled

North

Trawl

Station Depth (m) 12-15

South

17 lun

Trawl

South

19 Aug

Trawl

South

Total

(5 fish, 23-31 mm) from depths of 3 to 15 m at the north transect and 6 to 15 m at the south transect. Larvae apparently were restricted to deep water after May, since three fry (37-43 mm) were trawled on 17 June from the 12- and 15-m contours, and on 19 August another three fry (55-62 mm) were trawled at 15 m. Most fry (50 of 60 fish) were captured during night sampling. Lake trout hatch at about 15 mm (Daly, Hacker, and Wiegert 1969). Newly hatched lake trout contributed to the Great Lakes Regional Fish Larvae Collection (Dorr and Jude, in press) by Michigan's Marquette Fish Hatchery had mean lengths of 18.1 mm 1day after hatching and 20.8 mm 2 days after hatching. Compared with known-age Lake Michigan and Marquette Hatchery lake trout reared at the U.S. Fish and Wildlife Service Great Lakes Fishery Laboratory in Ann Arbor, fry we collected were estimated to have hatched in late February-March, 1980. As of fall 1979, when lake trout were moving inshore to spawn, an extensive area of rocky substrate covering the Campbell Plant's new Unit 3 offshore intake and discharge structures was available to the fish at all depths to 11 m (Figure 1). In contrast, most of the inshore zone of southeastern Lake Michigan is characterized by sandy substrate. Lake trout are apparently very selective in choosing spawning habitat (DeRoche 1969). They spawn in areas with rocky reefs and shoals, although seemingly suitable habitat sometimes shows no evidence of lake trout spawning. Deep cracks and

9 6-9 9 3-15 6-15 6-15 15 12 15 15

Diel Period Night Day Night Day Night Day Night Day Night Day Night

Fish collected Length Range (mm) No. 2 1 21 I

4 4 21 2 1 2 1 60

26-27 23 22-34 30 23-31 30~34

25-35 37-43 41 60-62 55 22-62

crevices in the substrate, such as provided by the Campbell Plant riprap, appear to be important factors for survival and subsequent hatching of eggs (DeRoche 1969, Stauffer and Wagner 1979). During fall 1979 we gillnetted 84 ripe or spent lake trout at both transects (Jude et ai. 1980). In November, the month of peak spawning activity, most adult lake trout were collected in the vicinity of the rock-covered structures. Lake trout eggs were found in the stomach of a round whitefish, providing further evidence of lake trout spawning in the area. Appearance of lake trout fry at the south transect, 3.1 km south of the area in which we believe they hatched, suggests either extensive movement by these fish or drifting with currents, or both. Young lake trout apparently disperse gradually and at random after hatching, then move offshore to deeper water after the yolk sac is absorbed and feeding has begun at a length of about 25 mm (Eschmeyer 1957, DeRoche 1969, Stauffer 1978b). During June, we caught lake trout fry only at 12and 15-m depths. No lake trout fry were collected in July when water temperatures were 16.0-23.0° C. However, in August, three fry were collected at 15 m where water temperatures were 7.0-7.5° C because of an upwelling of cooler hypolimnetic water. These observations indicate that some lake trout fry were inhabiting the hypolimnion in the general vicinity of the spawning site 6 mo after hatching. Several hypotheses for lack of natural reproduction in the past have been advanced:

60

JUDE, KLINGER, and ENK

1) Hatchery personnel planted most lake trout at accessible shoreline sites to which trout later home as spawning adults. Unfortunately, these sites provide no suitable spawning substrate; deposited eggs are subjected to wave and ice scour or sedimentation (Rybicki and Keller 1978). We have observed high densities of ripe and spent lake trout in nearshore areas of southeastern Lake Michigan during the fall spawning season (Jude et ai. 1979a, 1979b). However, in northern Lake Michigan, a substantial number of adult hatchery trout that return to shoreline planting sites are straying onto traditional nearshore spawning reefs (Peck 1979). 2) Toxic accumulations of contaminants (PCB, DDT, dieldrin, etc.) in eggs inhibited development or killed larvae when they absorbed the yolk sac. However, successful rearing of Lake Michigan lake trout eggs in Lake Michigan and in the laboratory casts serious doubt on this hypothesis (Stauffer 1979a). 3) Eggs laid were destroyed by fish or crayfish predation or were suffocated by excessive deposition of sediment and organic debris caused by increased erosion and eutrophication in the Lake Michigan basin over recent years. Although some studies have found little significant predation on lake trout eggs and fry (Peck 1979, Stauffer and Wagner 1979), protection afforded eggs and larvae by the many deep interstices of the Campbell Plant riprap may have contributed to successful lake trout spawning. Also, little sedimentation had occurred over the riprap by late fall 1979. Successful spawning near the Campbell Plant was probably related to the newly placed riprap. We have made similar monthly collections for 8 yr (Jude et ai. 1975, 1979b) at the Donald C. Cook Plant (about 100 km south; Figure 1) and have never captured lake trout fry, although ripe-running trout are regularly observed and collected during fall in the vicinity of the intake and discharge structure riprap. We have also found lake trout eggs in fish stomachs and onshore after a severe November storm (Jude et ai. 1979b). In Lake Superior, where both hatchery and remnant native stocks of lake trout exist, successful reproduction occurred over newly laid 5- to 46-cm crushed limestone covering a power plant discharge pipe in 2-9 m of water (Stauffer 1978a, 1979b). Lake trout show considerable alongshore movement in shallow water during the fall spawning season (Jude et ai. 1975). Because riprap at the Campbell Plant extended from very shallow water continuously to a depth of approximately 11 m, lake

trout homing to shallow water in this area of Lake Michigan and moving along shore would have intersected this ideal spawning substrate. ACKNOWLEDGMENTS This project was funded by Consumers Power Company, Jackson, Michigan. We thank R. Bailey and R. Miller, Museum of Zoology, University of Michigan, and M. Mac, USFWS Great Lakes Fishery Laboratory, for verifying our fry identification, and S. Corey for map illustration. Field work was performed by G. Heufelder, N. Auer, H. Tin, T. Rutecki, P. Schneeberger, and C. Madenjian. S. Spigarelli, D. Coble, and F. Tesar provided critical reviews. Contribution Number 304, Great Lakes Research Division, University of Michigan. REFERENCES Christie, W. J. 1974. Changes in the fish species composition of the Great Lakes. J. Fish. Res. Board Can. 31 :827-854. Crowe, W. R. 1975. Great Lakes Fishery Commission: history, program, and progress. Great Lakes Fish. Comm. Ann Arbor, MI Daly, R., Hacker, V. A., and Wiegert, L. 1969. The lake trout: its life history, ecology and management. Pub!. No. 233-69. Wis. Dept. Nat. Res., Madison, WI DeRoche, S. E. 1969. Observations on the spawning habits and early life history of lake trout. Prog. FishCult. 31:109-113. Dorr, J. A. III, and Jude, D. J. In press. Organization and status of a cooperative Great Lakes regional fish larvae collection. J. Great Lakes Res. Eschmeyer, P. H. 1957. The lake trout (Salvelinus namaycush). Fishery Leaflet 441. U.S. Dept. of InteriOl:, Fish and Wildlife Service. Washington, D.C. Jude, D. J., Tesar, F. J., Dorr III, J. A., Miller, T. J., Rago, P. J., and Stewart, D. J. 1975. Inshore Lake Michigan fish populations near the D. C. Cook Nuclear Power Plant, 1973. Spec. Rep. No. 52. Great Lakes Res. Div., Univ. Mich., Ann Arbor, MI _ _ _ _ , Heufelder, G. R., Tin, H. T" Auer, N. A., Klinger, S. A., Schneeberger, P. J., Madenjian, C. P., and Rago, P. J. 1979a. Adult, juvenile and larvalfish in the vicinity of the J. H. Campbell Power Plant, eastern Lake Michigan, 1978. Spec. Rep. No. 73. Great Lakes Res. Div., Univ. Mich., Ann Arbor, MI _ _ _ _ , Tesar, F. J., Tomlinson, J. c., Miller, T. J., Thurber, N. J., Godun, G. G., and Dorr III, J. A. 1979b. Inshore Lake Michigan fish populations near the D. C. Cook Nuclear Power Plant during preoperational years-1973, 1974. Spec. Rep. No. 71. Great Lakes Res. Div., Univ. Mich., Ann Arbor, MI

NOTE-LAKE TROUT REPRODUCTION IN LAKE MICHIGAN - - - - , Heufelder, G. R., Auer, N. A., Tin, H. T., Klinger, S. A., Schneeberger, P. J., Madenjian, C. P., Rutecki, T. L., and Godun, G. G. 1980. Adult, juvenile, and larval fish populations in the vicinity of the J. H. Campbell Power Plant, eastern Lake Michigan, 1979. Spec. Rep. No. 79. Great Lakes Res. Div., Univ. Mich., Ann Arbor, MI Peck, J. W. 1979. Utilization oftraditional spawning reefs by hatchery lake trout in the upper Great Lakes. Fish. Res. Rep. No. 1871. Mich. Dept. Nat. Res. Fish. Div., Lansing, MI Rybicki, R. W., and Keller, M. 1978. The lake trout resource in Michigan waters of Lake Michigan, 1970-1976. Fish. Res. Rep. No. 1863. Mich. Dept. Nat. Res. Fish. Div., Lansing, MI Smith, S. H. 1968. Species succession and fishery· exploitation in the Great Lakes. J. Fish. Res. Board Can. 25:667-693. - -__ . 1972. Factors of ecologic succession in oligotrophic fish communities of the Laurentian Great Lakes. J. Fish. Res. Board Can. 29:717-730. State of Michigan. 1966. Cumulative supplement of 1963 revisions of laws relating to conservation, Rule 299.791, p. 53. Stauffer, T. M. 1978a. Develop methods of capture and assess early survival of young lake trout in Lakes

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Superior and Michigan, pp. 243-249. In DingellJohnson Ann. Prog. Rep. F-35-R-4. Mich. Dept. Nat. Res. Fish. Div., Lansing, MI _ _ _ _ . 1978b. Behavior of age-O and age-l lake trout under laboratory conditions. Fish. Res. Rep. No. 1857. Mich. Dept. Nat. Res. Fish. Div., Lansing, MI _ _ _ _ . 1979a. Effects of DDT and PCB's on survival of lake trout eggs and fry in a hatchery and in Lake Michigan, 1973-1976. Trans. Amer. Fish. Soc. 108: 178-186. _ _ _ _ . 1979b. Develop methods of capture and assess early survival of young lake trout in Lakes Superior and Michigan, pp. 147-150. In DingellJohnson Ann. Prog. Rep. F-35-R-5. Mich. Dept. Nat. Res. Fish. Div., Lansing, MI _ _ _ _ , and Wagner, W. C. 1979. Fish predation on lake trout eggs and fry in the Great Lakes, 1973-1978. Fish. Res. Rep. No. 1864. Mich. Dept. Nat. Res. Fish. Div., Lansing, MI Van Oosten, J. 1946. A definition of depletion of fish stocks. Trans. Amer. Fish. Soc. 76:283-289. Wagner, W. C. 1980. Reproduction of planted lake trout in Lake Michigan. Fish. Res. Rep. No. 1885. Mich. Dept. Nat. Res. Fish. Div., Lansing, MI Yocum, W. L., and Tesar, F. J. 1980. Sled for sampling benthic fish larvae. Prog. Fish-Cult. 42:118-119.