1. Fig.1 – Fecundity of Great Lakes cisco as a function of length. Fig.2 – Fecundity of Great Lakes salmonids as a function of length 1 Eggs measured 1 – 65 days post spawning (N=1161). 2 Lake trout Sicowet strain Table 1 – Size of eggs from selected Great Lakes coregonids and salmonines. Discussion Although these data are based on an array of studies conducted over a large span of time and in limited regions of the Great Lakes, they suggest that fecundity of ciscoes are much great than that of bloaters, round whitefish, and possibly lake whitefish. Based on recent data and previous published studies (1950’s and 60’s), fecundity of large ciscoes (over 45 cm long) in Lake Michigan appeared to be significantly greater than that for ciscoes from Lake Superior, but not Lake Huron. Fecundity data for ciscoes is very limited (N=14) for Lake Ontario. A few ciscoes have been recently captured in Lake Erie (Cold Water Task Group, 2015), but no data were found on fecundity or egg size for fish from that lake. More data are needed to learn if fecundity for ciscoes in Lakes Erie and Ontario differ from that of the other lakes. Because of their small size at sexual maturity, maximum fecundity for bloaters and round whitefish were low in comparison to ciscoes and lake whitefish. Fecundity of two Great Lakes salmonines (Atlantic salmon and lake trout) were comparable to that of bloaters and round whitefish. Diameters of eggs of coregonids (0.6 to 3.5 mm) were smaller than those for the lake trout and Atlantic salmon (3.4 to 6.9 mm) and tended to be inversely correlated to fecundity of the species we examined. Among the salmonids examined, ciscoes appear to have the highest reproductive potential, making them good candidates for restoration. Results Figure 1 Fecundity for ciscoes ranged from approximately 3,000 to 109,000 eggs for individuals ranging from 21 to 55 cm in total length. Fecundity equations derived for Lakes Michigan, Superior, Huron, and Ontario were: F = 0.0154L t 3.8983, F = 0.1942L t 3.1906, F = 0.0691L t 3.5191, and F = 0.1178L t 3.4557 respectively. ANCOVA and AIC statistical tests showed that a four-lake model fit the data better than a single-lake model for all lakes. All pair-wise comparisons of the length x lake interaction (using the Bonferonni adjustment) between lake populations showed only one significant difference between lakes: Superior vs. Michigan (P<0.05). Figure 2 Fecundity of ciscoes appears somewhat greater than that of lake whitefish and much greater than that of bloaters, round whitefish, lake trout, and Atlantic salmon. Table 1 Diameters of eggs of coregonines (0.6 to 3.5 mm) were smaller than those for the lake trout and Atlantic (3.4 to 6.9 mm). The average diameter of cisco eggs were slightly larger than that of lake whitefish and intermediate in size with those of round whitefish being the largest and those of bloater being the smallest. Eggs of lake trout and Atlantic salmon were considerably larger than that for ciscoes. Introduction Cisco (lake herring, Coregonus artedi Lesueur, formerly Leucichthys artedi), along with lake whitefish (Coregonus clupeaformis) supported major commercial fisheries with cisco an important prey for lake trout (Salvalinus namyacush) in all the Great Lakes and probably for Atlantic salmon (Salmo salar) in Lake Ontario. Other ecologically important coregonids in the Great Lakes include round whitefish (Prosopium cylindraceum) and bloater (Coregonus hoyi). However, overfishing and other factors reduced populations with commercial catches of nearly 50 million pounds (e.g. Lake Erie: 1918) declining to < 2 million by the 1930s and region-wide collapse by the 1960s (Van Oosten 1930). Today, ciscoes are found primarily in Lake Superior and, in reduced numbers, in Lake Huron, with only remnant populations remaining in Lake Michigan, Lake Ontario, and possibly Lake Erie (Stockwell et al. 2009). Fecundity along with egg size are important metrics for understanding adaptive strategies and predicting recovery potential. However, studies on fecundity have been limited to restricted geographic areas within the Great Lakes region. The objectives of this study were to (1) review and summarize fecundity studies on ciscoes, (2) derive fecundity equations of contemporary populations, and (3) compare cisco fecundity and egg size to that of other species of salmonids in the Great Lakes. Methods We reviewed studies that reported fecundity (# of eggs/female) and egg size of cisco and other Great Lakes coregonids and salmonines. Some of the 480 fecundity values ciscoes obtained represent means of multiple females. Co-authors Myers and Yule collected ciscoes at five sites in Lake Superior, two in Lake Huron, and one in Lake Michigan to determine fecundity (F) equations (F = aL t b ) where L t is total length in centimeters, and ‘a’ and ‘b’ are best-fit parameters. Fecundity equations were also developed for bloater, lake whitefish, round whitefish, and lake trout based on data in the literature. Fecundity data for Atlantic salmon (Salmo salar) were obtained from Roger Greil (Lake Superior Fish Hatchery Lower Lake Superior University Aquatic Research Laboratory, Sault Ste. Marie, MI). The statistical program R was used to compute analysis of covariance (ANCOVA), and Akaike’s Information Criterion (AIC) was used to compare a single model (fecundity vs. total length) for all lakes using 480 females against a four-lake model. We also tested for statistical significance of all possible pairings for the four lakes using the Bonferroni adjusted significance level. Average egg size data was obtained from the literature and 1,161 eggs we obtained from ciscoes that were captured in Chaumont Bay at the eastern end of Lake Ontario between 2011 to 2015. Abstract Understanding fecundity of Great Lakes cisco is fundamental to their management. We summarized published (1938 – 1964) studies of egg production by ciscoes from the Great Lakes. Fecundity data from these studies were combined with data the we collected (2008 - 2015) and used to compute fecundity (F = a L t b ) as a function of fish total length (L t ). Best fit cisco fecundity equations for Lakes Superior, Michigan, Huron, and Ontario were, F = 0.1942L t 3.1906, F = 0.0154L t 3.8983, F = 0.0691L t 3.5191, and F = 0.1178L t 3.4557, respectively. and was F = 0.0572L t 3.5475 for all lakes combined. Models were also developed for lake whitefish (F = 0.002L t 4.1287 ), and bloater (F=0.7332L t 2.7982 ). Fecundity of two Great Lakes salmonines (Atlantic salmon and lake trout) were comparable to that of bloaters and round whitefish, but were larger were larger at maturity. Diameters of eggs of coregonids (0.6 to 3.5 mm) were smaller than those for the lake trout and Atlantic salmon (3.4 to 6.9 mm). Among the coregonids we examined, ciscoes appear to have the highest reproductive potential, making them good candidates for restoration. James D. McKenna, H. George Ketola, Jared T. Myers 1, Daniel L. Yule 2, and Marc A. Chalupnicki US Geological Survey, Great Lakes Science Center, Tunison Laboratory of Aquatic Science, Cortland, NY 1 Graduate student, Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 2 USGS Great Lakes Science Center, Lake Superior Biological Station, Ashland, WI Comparison of fecundity and egg size of cisco (Coregonus artedi) to other salmonids in the Great Lakes Acknowledgment: We thank Jean Adams (US Geological Survey, Ann Arbor, MI) for her assistance with statistical analyses.. Lake Michigan F = 0.0154L 3.8983 R² = 0.87 Lake Ontario F = 0.1178L 3.4557 R² = 0.94 Lake Superior F = 0.1942L 3.1906 R² = 0.75 Lake Huron F = 0.0691L 3.5191 R² = 0.53 LakeSpecies Egg Dia. mm (Range) Ref. # Eriecisco2.0 (1.8 – 2.1)10 Ontariocisco 1 2.5 (1.5 – 3.4)This Study lake whitefish8.6 mg (SD=1.36)9 Michiganbloater1.3 (0.6 – 2.1)6 lake whitefish2.8 (2.3 – 3.0)1, 8 lake trout5.2 (4.9 – 5.6)1, 10 Huronlake whitefish7.4 mg (SD=1.69)9 Superiorbloater1.9 (1.8 – 2.1)1, 8, 5 round whitefish3.2 (2.9 – 3.5)1, 8 lake trout4.6 (3.8 – 5.4)7 lake trout 2 4.6 (3.4 – 5.4)7 ChamplainAtlantic salmon5.7 (5.1 – 6.9)This study Source data Lake Michigan – (N=114) Smith (1956) Myers (2010) Lake Superior – (N=230) Dryer & Beil (1964) Myers (2010) Lake Huron – (N=122) Myers (2010) Lake Ontario – (N=14) Stone (1938) Shaded area represents 95% C.I. References Cited (1) Auer, N. A. 1982. Identification of larval fishes of the Great Lakes basin with emphasis on the Lake Michigan drainage. 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