Genetic population structure of muskellunge (Esox masquinongy) in the Great Lakes

We are in the late stages of preparing this work for publication.  Our abstract, etc. will be posted once they have passed internal review…stay tuned!

Objective: The objective of our study was to determine if inter-population diversity and genetic spatial structure exists among the putative muskellunge populations in the Great Lakes.  Our goal was to quantify this diversity and structure to inform management plans that will be effective at conserving the species’ evolutionary potential.  In addition, we discuss how patterns in genetic structure relate to results of muskellunge movement studies that indicated reproductive homing, and how within-population diversity of muskellunge compares to other freshwater fishes.

Coauthors: Brian Sloss (USGS/UW-Stevens Point) and John Farrell (SUNY-ESF)

First Report of Abundant Rudd Populations in North America

In 2007-2008, we captured thousands of rudd in trap-nets set in the Buffalo Harbor and upper Niagara River.  The nets were set in shallow waters (≤ 2m) during May and June to sample muskellunge for research purposes and to assess the fish community more generally.  To our surprise, the rudd dominated our catches.  We authored a Management Brief that will soon be published in the North American Journal of Fisheries Management to document these populations and motivate future research.

More to follow…

Title:  First Report of Abundant Rudd Populations in North America

Abstract:  Rudd Scardinius erythrophthalmus were first introduced to U.S. waters about a century ago, and its popularity as a bait fish in the 1980s facilitated its spread to at least 21 states and Ontario, Canada.  Several established populations have been identified, but low abundances led to little research and management attention.  Rudd comprised 48.7% of the 14,130 fishes captured in spring trap-netting surveys of the Buffalo Harbor (northeastern Lake Erie) and upper Niagara River during 2007-2008.  Rudd was the most abundant species sampled, captured at 11 of 12 locations, and comprised 23.6% of the total catch in the Buffalo Harbor and 70.3% in the upper Niagara River.  Documented presence and absence in historical reports indicates the rudd became established between 1986 and 1991 in these waters.  Research is needed to understand the effects of rudd on native aquatic resources, especially nearshore macrophyte
assemblages and the fishes they support.

Coauthors: John M. Farrell (SUNY-ESF) and Michael A. Wilkinson (NYSDEC)

Habitat-Fish Assemblage Relations

Here is a title and abstract from a paper we are working on that investigates which habitat variables influence nearshore fish assemblages, and how this relates to predators such as muskellunge.  More details to follow…

Title: Habitat Factors Influencing Fish Assemblages at Nearshore Sites of Two Great Lakes Connecting Channels: Implications for an Apex Predator

Abstract: Nearshore sites of the Great Lakes and their connecting channels provide critical nursery habitat for important piscivores such as muskellunge (Esox masquinongy) and the fishes they prey upon.  However, our poor understanding of habitat-fish assemblage relations compromises our ability to manage and restore these communities.  Therefore, we (1) described assemblages at sites in the Buffalo Harbor (Lake Erie), upper Niagara River, and St. Lawrence River, (2) compared assemblages among sites and water bodies, and (3) determined if differences among assemblages were related to habitats variation.  Mean fish density was almost eight times higher at Niagara River sites than at St. Lawrence River sites and five times higher than at Buffalo Harbor sites.  Sites that had flowing water, coarse substrates, complex aquatic vegetation, and little or no macroalgae were dominated by small-bodied cyprinids, which are typically broadcast spawners and require complex habitats for refugia from predation.  Conversely, lentic sites with fine substrates, sparse vegetation, and dense macroalgae were dominated by larger-bodied centrarchids and yellow perch (Perca flavescens) whose reproductive strategies and anti-predator adaptations allow them to persist in such habitats.  Young-of-the-year muskellunge typically avoid feeding on centrarchids and yellow perch, so habitats that support abundant small-bodied fishes should provide better nursery conditions and promote stronger year-class formation.

Coauthor: John M. Farrell

Contaminants in Rudd

Here is a title and abstract from a paper we are working on examining contaminant levels in rudd.  More details to follow…

Title: Low Concentrations of Contaminants in an Invasive, Macrophyte-eating Cyprinid, the Rudd

Abstract: The invasive, macrophyte-eating rudd (Scardinius erythrophthalmus) is relatively abundant in the Buffalo Harbor (Lake Erie) and upper Niagara River, a Great Lakes Area of Concern.  Because aquatic macrophytes have been shown to sequester toxic metals, we hypothesized that rudd were acquiring contaminants through their diet.  Therefore, we examined rudd and nine other fish species from various trophic levels for a suite of contaminants.  We found that rudd contained low concentrations of mercury (mean = 0.033 μg/g), total polychlorinated biphenyls (mean = 0.081 μg/g), and total dichlorodiphenyltrichloroethane (mean = 0.005 μg/g), and that concentrations were lower than those found in all other species examined.  Concentrations of aldrin, heptachlor, hexachlorobenzene, hexachlorocyclohexanes, mirex, and total chlordanes were less than the method detection limit for all rudd examined.  Consequently, we reject our hypothesis that rudd were assimilating significant concentrations of toxic substances by feeding on macrophytes.  However, tests of contaminant concentrations in macrophytes are needed to determine if rudd are relocating contaminants by feeding on macrophytes.

Coauthors: John M. Farrell (SUNY-ESF), Michael A. Wilkinson (NYSDEC), Lawrence C. Skinner (NYSDEC, retired), and Anthony J. Gudlewski (NYSDEC)

Feeding Ecology and Population Structure of the Invasive Rudd in the Buffalo Harbor and Upper Niagara River

Here is the title and abstract of a paper we are working on regarding the invasive rudd.  More details to follow…

Title:  Feeding ecology and population structure of an invasive cyprinid, the rudd, in the Buffalo Harbor (Lake Erie) and upper Niagara River

Abstract: The rudd Scardinius erythrophthalmus Linnaeus, an invasive cyprinid, was the most abundant fish in trap-net catches in the Buffalo Harbor and upper Niagara River during May and June 2007-2008 (49% of total catch), causing concern about their potential effects on the ecosystem.  Therefore, we conducted a study in 2009 to examine rudd feeding ecology, condition, and growth, used data from 2007-2010 standardized seining surveys to quantify reproductive success at sites with different flow conditions.  Rudds were mostly herbivorous; they consumed aquatic macrophytes in summer and supplemented their diet with algae and fish during spring and fall.  The percentage of rudds that contained food and the weight of food as a percentage of total body weight indicated that feeding intensity was positively correlated with water temperature, but
significantly reduced during spawning.  Rudd condition and growth were greater than available estimates from other populations, suggesting increases in abundance and range expansion are possible.  Furthermore, reproduction was successful at lotic sites but very poor at sites that lacked measureable flow, so the paradigm of optimal rudd habitat and water bodies vulnerable to invasion should be expanded to include lotic systems.  The rudd possesses several adaptations that make it a successful invader, including the ability to consume macrophytes that are underutilized by most native north temperate freshwater fishes in North America.  Research is needed to understand how herbivory by rudd populations affects native aquatic communities.

Coauthors: John M. Farrell (SUNY-ESF) and Michael A. Wilkinson (NYSDEC)

Emerald Shiner Migrations

Emerald shiners are small minnows native to North America.  They feed primarily on zooplankton, especially cladocerans (Hartman et al. 1992).  Every year in spring/early summer, adult emerald shiners migrate downstream from Lake Erie into the upper Niagara River to spawn.  During late summer, their young move upstream back to the lake, in numbers that are simply amazing.  I was lucky enough to witness this on 4 August 2010, when young-of-the-year emerald shiners swam past us in a steady parade the entire time we were sampling – for the better part of an hour.  Then we caught thousands of them in our seine.  Check out the photos below.   How important must these little fish be to the ecosystem?

Young-of-the-year emerald shiners

Emerald shiners caught in our seine

Reference

Harman, K. J., Vondracek, B., Parrish, D. L., and K. M. Muth.  1992.  Diets of emerald and spottail shiners and potential interactions with other western Lake Erie planktivorous fishes.  Journal of Great Lakes Research 18(1): 43-50.

Peer-reviewed Journal Articles

Here is a list of publications I have coauthored.  A PDF of the walleye paper is available through my Great Lakes Fishery Commission link.   Scroll down to Technical Reports and click on Status of Walleye in the Great Lakes: Proceedings of the 2006 Symposium; our contribution starts on page 15.  Send me an email if you want a PDF of another paper.

Kapuscinski, K. L., Farrell, J. M., and M. A. Wilkinson.  In Press.  First report of abundant rudd populations in North America.  North American Journal of
Fisheries Management

Kapuscinski, K. L., Zorn, T. G., Schneeberger, P. J., O’Neal, R. P., and B. T. Eggold.  2010.  The status of Lake Michigan walleye stocks.  In Status of walleye in the Great Lakes: proceedings of the 2006 Symposium. Great Lakes Fishery Commission Technical Report 69. pp. 15-70.

Kapuscinski, K. L., Belonger, B. J., Fajfer, S., and T. J. Lychwick.  2007.  Population dynamics of muskellunge in Wisconsin waters of Green Bay, Lake Michigan, 1989–2005.  Environmental Biology of Fishes 79:27-36.

Kapuscinski, K. L., Hansen, M. J., and S. T. Schram.  2005.  Movements of Lake Trout in U.S. Waters of Lake Superior, 1973-2001.  North American Journal of Fisheries Management 25:696-708.

Diets of Young-of-the-year Muskellunge

Coauthors

Dr. John M. Farrell (SUNY-ESF) and Dr. Brent A. Murry (Central Michigan University) contributed to the data collection, analysis, and authorship of a journal article that will be peer reviewed and published on this subject matter.  However, they had not input on this blog, so any errors below are my own.

Management Problem / Ecological Questions

Our ability to conserve muskellunge is compromised because several questions about their feeding ecology remain unanswered.  For example, it is difficult to protect or restore optimal nursery habitats if we don’t know what fishes muskellunge rely upon for food during their first growing season.  Therefore, we analyzed data collected on young-of-the-year (YOY) muskellunge from St. Lawrence and upper Niagara River nursery habitats to answer three important questions.  First, do diets of muskellunge reared in lentic (still-water) and lotic (flowing-water) nursery habitats differ?  Second, do muskellunge feed selectively on different prey fishes, especially recently introduced prey (e.g. round goby)?  Third, do muskellunge select prey based on length?

Methods

We captured YOY muskellunge by seining and electrofishing, and extracted stomach contents via gastric lavage (stomach flushing).

 

Flushing out stomach contents

 

 

Retrieving prey fish with tweezers

 

 

Banded killifish retrieved from muskellunge stomach

 

All muskellunge were measured for total length and released.  Prey fish recovered from muskellunge stomachs were identified and measured for total length when possible (some were digested).

We compared the diets of muskellunge from the St. Lawrence and Niagara Rivers based on the percent composition by number and weight of different prey types.  We also compared the proportion of prey fish in the diet to that in the field (seine catches) to determine if muskellunge fed selectively.  Finally, we determined if prey were selected based on size by comparing the length of muskellunge and their prey.

Results

Banded killifish was the most important prey type in the St. Lawrence River (44% by number, 50% by weight) and the second most important in the upper Niagara River (27% by number, 23% by weight).

 

Banded killifish

 

Native minnows were the most important prey type in the Niagara River (31% by number, 33%) and second most important in the St. Lawrence River (15% by number, 11% by weight).  Darters were also important in both rivers.

Muskellunge from both habitats preyed selectively upon banded killifish, darters, and non-native round goby, and non-native minnows (carp/goldfish) were selected in lotic habitats; sunfish (pumpkinseed, bluegill, and bass) and native minnows were consumed at lower proportions than were available.

Prey length ranged from 6% to 58% of muskellunge length, and increased with muskellunge length in both habitats.

Conclusions

YOY muskellunge in both rivers fed heavily on a single species, the banded killifish.

The presence of round goby in diets of YOY muskellunge from the St. Lawrence and Niagara Rivers in 2009 is the first record of this occurrence.  It is uncertain whether predation on round goby will benefit muskellunge populations via energetic gain or harm them via disease related mortality.

 

Round goby

 

YOY muskellunge typically selected elongated, soft-rayed fishes as prey and avoided deep-bodied, spiny-rayed fishes like pumpkinseeds and yellow perch.

 

Spottail shiner (photo by Konrad Schmidt)

 

Which would you rather try to swallow whole, the shiner above or the yellow perch below?  Consider the body shapes and whether or not the fin rays are spiny.

 

Yellow perch (photo by M. Gautreau)

 

Consistent patterns in selective feeding by muskellunge were observed across habitats, and selection for non-native prey suggests that muskellunge broadened their diet in response to some introduced fishes (round goby) but not others (rudd).

Management Implications

How do we manage for healthy populations of the prey fish important to YOY muskellunge (banded killifish, minnows, & darters)?  These species prefer habitats with clean substrates and healthy aquatic vegetation, so we should protect nearshore areas from dredging and shoreline development, and support management practices that reduce silt loads (e.g. storm water retention, restoring riparian habitats, etc.).