EPA/600/A-97/089


                                                                           Whittier   1
                   Development of IBI metrics for lakes in southern New England

                                    Thomas R. Whittier
                                 Dynamac International, Inc.
                                     200 SW 35th St.
                                   Corvallis, OR 97333
                                 whittier@heart.cor.epa.gov
                                      541-754-4455

 I.     INTRODUCTION
 2.     IMPEDIMENTS TO DEVELOPING LAKE IBIS
 2.1    SCOPE OF ASSESSMENT
 2.2    SAMPLING ISSUES
 2.3    PUBLIC PERCEPTIONS AND MANAGEMENT OF LAKES
 2.4    ECOLOGICAL FACTORS
 3.     METHODS
 3.1    SAMPLE DESIGN & FIELD METHODS
 3.2    QUANTITATIVE METHODS
 4.     RESULTS
 4.1    SPECIES RICHNESS METRICS
 4.2    TROPHIC COMPOSITION METRICS
 5.     DISCUSSION

 Submitted as a chapter in Assessing the sustainability and biological integrity of water resource quality using
 fish assemblage. Thomas P. Simon (ed). CRC Press. Boca Raton, FL.

The research described in this article has been fimded by the U.S. Environmental Protection Agency. This
document has been prepared at the EPA National Health and Environmental Effects Research Laboratory,
Western Ecology Division, in Corvallis, Oregon, through Contract 68-C5-0005 to Dynamac International
Corp. It has been subjected to the Agency's peer and administrative review and approved for publication.
Mention of trade names or commercial products does not constitute endorsement for use.

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                                         INTRODUCTION




 Among the principles implicit in the field of ecology are assumptions that: (1) living organisms react to




 changes in their ecosystems, (2) we should be able to detect and quantify changes in biological assemblages




 due to adverse stress caused by human activity, and (3) these changes should be predictable and generalizable




 to broad classes of ecosystems and assemblages. In the early 1980s Karr and his colleagues successfully




 applied these principles to fish assemblages in warmwater streams in the Midwest (Karr 1981,1991; Karr et




 aJ.  1986; Lyons 1992; OEPA 1988). The resulting Index of Biotic Integrity (DBI) has been repeatedly




 modified for other assemblages, regions and ecosystems (e.g., Leonard and Orth 1986; Miller et aJ 1988;




 Steedman 1988), with varying degrees of success.









 To date there has been only limited effort toward developing IBIs for lakes.  Minns et al. (1994) developed an




 eight metric IBI for littoral areas in the Great Lakes. Dionne and Karr (1992) and Jennings et al. (1995)




 presented preliminary results for a Reservoir Fish Assmeblage Index for the Tennessee Valley, but concluded




 that additional work was needed. The  only other published  research for inland lakes is in Wisconsin by




 Jennings et al. (this book). They evaluated metric variability related to sampling methods, and how the




 metrics performed as indicators of human induced stress.  They were satisfied with the performance of only




 four metrics.









 In this chapter, I review some of issues that may account for the apparent difficulty in developing inland lake




 IBIs. I then present an evaluation of several candidate metrics for lakes in southern New England, and discuss




some the implications of the results and needs for further research.

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                           IMPEDIMENTS TO DEVELOPING LAKE IBIS








 The reasons that development of lake IBIs lags behind that for warrnwater streams may be divided into four




 groups: (1) scope of assessment, (2) sampling issues, (3) perceived values of lakes and the management




 practices that support those values and (4) ecological factors. The issues discussed below are generalizations




 meant to emphasize differences, exceptions to each point can be found. Clearly, these concerns are not the




 exclusive domain of lake assessments.









 SCOPE OF ASSESSMENT




 For streams the conceptual and actual units for biological assessments are not entire streams, but rather




 separated points or reaches along the stream length.  In reporting results, the points or reaches are plotted or




 tabled as individual samples and the assessment of biotic condition usually integrates the individual samples




 and changes along the stream length. For lakes, the conceptual units are usually whole lakes, although




 sampling is usually at stations or portions of shoreline; and  the data are generally combined to represent the




 entire lake. Only when lakes are sufficiently large are sampling, analysis and assessment done on subunits




 (e.g., coves, bays, arms).









 Another facet of this issue is one of "apples and oranges". Biological assessments need to be developed for




 classes of reasonably comparable ecosystems (Plafkin et al. 1989). An IBI is based on expeeted-




characteristics of a particular assemblage type, in a particular size and type of waterbody, in a particular




ecoregion or basin. For streams, assemblage expectations are usually defined for ecoregion (or basin),




temperature type (cold or warm), and stream size. The classes of ecoregions and temperature types usually




can encompass a very large number of streams in the same assessment framework.

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                                                                                       Whitlier   4




 For lakes, classing waterbodies into reasonably comparable groups is more complex. Stream size describes




 habitat volume. Habitat volume in lakes is more multi-dimensional. Lake volume defines only the maximum




 possible habitat volume. The useable volume may be limited by oxygen depletion (either natural or amplified




 by anthropogenic eutrophication) and temperature extremes in summer or oxygen depletion in winter and thus




 may vary greatly within and among years. Natural differences in stratification regimes affect expectations for




 the fish assemblages, as does basin shape which determines the proportion of the habitat that is littoral versus




 pelagic. Watershed position and relative connectedness are also important; a large headwater lake or a large




 isolated lake could be expected to have a fish assemblage which differs from a large well connected lake




 closer to a mainstem river.









 SAMPLING ISSUES




 Biological assessments require data collected in a consistent manner, that represent or index the resident




 assemblages (Plafldn et al. 1989). For wadeable streams, electrofishing provides appropriate data for IB1




 assessments (e.g., OEPA 1988).  For lakes no single gear is sufficient to sample in all habitat types nor for all




 species. Numerous studies have examined the issue of gear selectivity, sufficiency of effort and sampling




 variability in northern lakes (e.g., Weaver et al. 1993). Whenever more than one gear or method is used,




 questions arise of how and whether to combine data, and what constitutes a unit of sampling effort Jennings




 et al. (this book) propose evaluating and using data from different methods for different metrics, as well as




 limiting the data collection to littoral assemblages.









 Problems with using multiple gear are compounded further when certain effective methods cannot be applied




 in all lakes. Night beach seining is often the only effective method for collecting cyprinids, darters and




sculpins, but many lakes lack beaches clear of obstacles, suitable for seining.  Electrofishing is a good single




method for sampling the littoral zone,  but losses its effectiveness in low conductivity lakes common in

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                                                                                      Whittier   5




 northern regions, and in lakes witli very narrow littoral zones.  Likewise, gill nets are the only reliable method




 for collecting salmonids and other pelagic species, but resource managers of low productivity northern lakes




 often restrict or forbid the use of gill'nets.








 PUBLIC PERCEPTIONS AND MANAGEMENT OF LAKES




 The public, and therefore management agencies, value different things about lakes than they value for




 streams. The public often values a park-like aesthetic for lakes, as a place for homes, vacation cabins, and




 parks for camping, picnics, and swimming. People like the water; they like to see it, be near it, on it, or in it,




 and often they want to use the water for drinking. Except for drinking water, lakes are more amenable to




 these things than are streams. Activities in, on, or near the water lead people to want water clear of obstacles




 (vegetation, snags, etc), for boating, fishing and swimming. And of course, people want good fishing,




 regardless of whether the desired species is native or even suited for "their" lake.









 Lakes are often managed to enhance the values listed above, usually to the detriment of biotic integrity.




 Snags and weeds are cleared for boating, swimming, docks, and front yard aesthetics. Retaining walls or




 riprap are added for erosion control (Jennings et al.  1996; Christensen et al.  1996). Lakes have been




 subjected to slocking and other manipulations of fish assemblages for well over a century. In southern New




 England much of the public is not aware that most of the currently widespread game fish are not native (e.g.,




 largemouth and smallmouth basses, bluegill, northern pike, black crappie, brown, rainbow and lake trouts).









 Management goals are closely linked with who does the managing.  Streams  tend to be managed by, or under




 the authority of state departments of environmental quality, who are concerned with issues defined by the




Clean Water Act and subject to oversight by the U.S. EPA.  This is in part due to historic problems from




point-source pollution on streams and rivers.  As the obvious water quality problems in streams are corrected,

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 many of these agencies are shifting their regulatory emphasis to the biological condition of streams, for which




 the IBI is well suited.









 Lakes, on the other hand, are managed by various legal entities. In some lake-rich regions where lakes receive




 more recreational use than streams, lakes in the public domain are often managed by state fish and game




 departments. Their mandates emphasize management for fishability, not biotic integrity. Unfortunately in




 some instances, interagency politics has led to lakes and streams becoming the exclusive territory of different




 agencies wherein environmental quality agencies often only become involved with lakes over eutrophication




 and fish tissue contaminants issues. Finally, unlike streams and rivers, lakes often have what amounts to




 owners: private individuals and families, lake and home owners associations, sports clubs, organization




 camps, resorts, and water districts. Technically many of these lakes are public, but in reality the owners of




 the land surrounding lakes limit access to and activities on "their" lake, and the public agencies often choose




 not to press their legal mandate.  It is reasonable to assume thai most lake owners do not manage for biotic




 integrity.








 ECOLOGICAL FACTORS




 In general, lakes tend to be new geographic features compared with rivers and streams, and fishes have had




 longer to speciate in, and adapt to flowing water.  Thus, there tends to be fewer lake-dwelling species. For




 example, in southern New England the regional species pool of lake dwellers is considerably smaller than the




 already depauperate species pool for lotic systems (Miller et al. 1988; Halliwell et al. This book).  There are




 only three native sunfish; pumpkinseed is nearly ubiquitous, and the other two are rather uncommon.




 Depending on the location, there  are one or two each of suckers, darters, and native top carnivores, and three




 to five possible lake-dwelling minnows (Whittier et al.  I997a). In addition, for more than a century the fish




fauna in New England has been liberally augmented with non-natives. In the Northeast an estimated 64% of

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 all lakes have at least one non-native species, with non-native individuals outnumbering the natives in 25% of




 lakes (T, Whittier unpub. data).  Introductions are especially common in southern New England where nearly




 all lakes have non-natives.









 Fish species' tolerances to stress (whether natural or anthropogenic) in lake ecosystems often differ from their




 tolerances in stream ecosystems. Whittier and Hughes (in review) evaluated 45 species' tolerances to five




 anthropogenic stressors in Northeast lakes. They found that eight species usually classified as tolerant or




 moderately tolerant of disturbance in streams appear to be intolerant or moderately intolerant of degraded




 conditions in lakes. Five species usually classified as intermediately tolerant in streams were very tolerant in




 Northeast lakes.








                                            METHODS









 SAMPLE DESIGN & FIELD METHODS




 The data used here were from the U.S. Environmental Protection Agency's Environmental Monitoring and




 Assessment Program (EMAP) Northeast Lakes Pilot (Larsen et al. 1991,1994; Stevens 1994). EMAP




 sampled fish assemblages, as well as water chemistry, zooplankton, physical habitat and riparian birds in 179




 lakes and reservoirs during the summers of 1992-94 in the Northeast USA (New England, New York, New




 Jersey). The lakes were selected, using a systematic random design, from all lakes > 1 ha. For this study, I




 used the 50 lakes in southern New England (MA, CT, RI and the southern 1/3 of NH) and five additional




 lakes, purposively selected and sampled in 1991 for methods evaluation (Larsen and Christie 1993).








Fish assemblages were sampled with overnight sets of gillnets, trapnets and minnow traps, and by night




seining (Whittier et al. 1997b). The level of effort was determined by lake size. The sampling objective was

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                                                                                      Whittier    8




 to collect a representative sample of the fish assemblage at each lake.  Sites were selected using a stratified




 random design. Littoral fish sampling was done at random stations within each macrohabitat class.  Pelagic




 sample sites were chosen in random directions from the deepest location. The collected fish were identified to




 species and counted. As part of the EMAP Quality Assurance procedures (Chaloud and Peck 1994)




 specimens of all species were vouchered with the Museum of Comparative Zoology at Harvard University to




 confirm identifications and for permanent archival. To develop the metrics evaluated in this study, I




 combined data from all gear. Water samples were collected at 1.5 m at the deepest part of the lake.  Field




 methods are detailed in Baker et al. (1997), which is available from the author. Field and laboratory data




 from the Northeast Lakes Pilot may be found on the EMAP's website (http://www.epa.gov/docs/emfjulte/




 htmJ/datal/surfwatr/index.html).








 QUANTITATIVE METHODS




 I chose two measures of anthropogenic stress to evaluate metric performance: total phosphorus (TP) as a




 measure of eutrophication stress, and the extent of human activity in the watershed as a measure of




 generalized human induced stress.  The latter is an indirect measure of stress, but is based on the premise that




 increased human activity in the watershed increases the frequency and strength of a multitude of




 anthropogenic perturbations to the lake ecosystem. Although acidification is also a stressor in some areas of




 the Northeast, only four of the sampled lakes in southern New England had pH<6.0. Preliminary examination




 of the fish assemblage data did not reveal any distinct qualitative acidification effects, thus I used pH stress




 only to aid interpretation of metric behavior.









Watershed-scale measures of human disturbance were developed from digitized coverages of human




population and road density (Census Bureau  1991; USEPA 1992), and land use/land cover (USGS 1990)




from which proportions of the watershed in urban,  industrial/commercial, residential, forested, wetlands and

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 agricultural categories were calculated (C. Burch Johnson, unpub. data). To estimate human disturbance in




 the watershed, I used the first axis scores of a principal components analysts (PCA) (Gauch 1982, PROC




 PRINCOMP; S AS 1985) of the land cover (% forest, % urban, % agricultural), human population density




 and road density, as described in Whittier et al. (1997a). The first principal component accounted for 62% of




 the variability in these five variables, with % forests loading negatively, and all human activity variables




 loading positively (Table 1).









 To determine species' native ranges I examined species maps and descriptions in a variety of fisheries texts




 (Kendall 1914; Hubbs and Cooper 1936; Hubbs and Lagler 1964; Scott and Grossman 1973; Lee et al. 1980;




 Trautman 1981; Becker 1983; Smith 1985; Schmidt 1986; Underhill 1986; Page and Burr 1991), and state




 biological survey reports from New York (NYSDC 1927-39) and New Hampshire (NHFGC 1937-39).




 Trophic guild and habitat preferences were based on these sources along with the summary tables Ln Halliweil




 et al (this book), Karr et al. (1986), Ohio EPA (1989), Lyons (1992), and Minns et al. (1994).  Most




 tolerance classifications were from Whittier and Hughes (in review); for the remaining uncommon species I




 used information contained in all of the above sources to make tolerance classifications.









 Due to the relatively low native species richness in New England, I anticipated that several commonly used




 metrics would not be effective. Thus, I examined a large number of potential metrics (e.g., Miller etal. 1988;




 Simon and Lyons 1995). To evaluate candidate metrics I considered the following: How many species




 contributed to the metric? What was the statistical distribution of raw scores among lakes? Was there a lake




 size effect? How do raw metric scores relate to the two measures of stress? In particular, do the raw metric




 values distinguish between the most degraded and the least degraded lakes? What ecological characteristics




do the metrics represent and how do we expect these to change over a range of natural conditions and human-

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 induced stress?  I primarily used a graphical-based approach (Fore et al. 1996),  examining scatterplots of




 raw metric data and residuals from regressions .








                                            RESULTS









 In the summers of 1991-94, EMAP sampled 55 lakes and reservoirs in southern  New England (SNE; Figure




 1). All, except three, lakes were <300 ha (Figure 2). Eighteen of the lakes are in the Northeastern Highlands




 ecoregion (NHE), with the remainder in the Northeastern Coastal Zone (NCZ) ecoregion (Omemik 1987).




 Ten lakes were eutrophic or hypereutrophic, with the remainder split between mesotrophic and oligotrophic




 (Figure 2a-b). Phosphorus values tended to be higher in NHE and in lakes <100ha. There was no association




 with lake size for watershed disturbance (Figure 2c-d).  Watersheds were less disturbed in NHE.  Water level




 control  structures are common on Northeast lakes (pers. obs.); 10 of SNE sample lakes have "Reservoir" in




 their names.  Named SNE reservoirs tend to be the larger lakes and have relatively low stressor values.









 Forty fish species were collected, 18 of which are native to the region, 20 are introduced and two are native to




 some of the lakes (Table 2). Of the 40 species collected, 18 were found in three or fewer lakes. Assemblages




 were characterized by centrarchids, yellow perch, chain pickerel,  golden shiner and bullheads. Bluegill tended




 to dominate in the south, being replaced by yellow perch to the north.









 SPECIES RICHNESS METRICS




 Nearly all of the original (Karr 1981) and variants (Miller et al. 1988; Simon & Lyon 1995) of the species




richness metrics were problematic in SNE.  The total number of species EMAP collected was similar to the




total (44) used by Minns et al. (1994) in the Great Lakes. But slightly more than half of the SNE species are




not native to New England, compared to 25% non-native species  collected by Minns et al.  Many  of the New

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 England non-natives were introduced 100+ years ago and are firmJy established (NHFGC 1937-39). Some




 authors suggest that these species are now "naturalized" and should be considered as part of the resident




 species pool (Halliwell et al, this book).  Under that proposal only the two non-North American species




 (common carp and brown trout) and populations maintained by stocking (nearly always salmonids in SNE)




 could be considered non-native. There'are currently no state run warm-water species stocking programs in




 SNE (D. Halliwell pers. comm.) I followed a strict interpretation of native status for this assessment









 The number of native species in SNE lakes increased with lake size (^=0.41, p=0.0001; Figure 3a),  ranging




 from 2  to 9 species (11 in one lake). Two features of these data differed from those in Midwestern streams.




 First, there were apparently no fisWess lakes in SNE, while some fairly large streams (watersheds up to 2000




 km2) in Ohio were fishless (Whittier and Rankin 1992). Second, the data formed a band rather than  a wedge




 shape (i.e., variance about the regression line was fairly constant rather than increasing with  lake size). To be




 a useful metric native species richness residual scores, from the regression with lake size, should generally




 decrease with increasing stressor scores (i.e.,  fewer than "expected" natives in more stressed lakes and more




 native species in less stressed lakes). However, there was no apparent pattern in these data (Figure 3b-c).




 Jennings et al. (this book) also found no relationship between native species richness and human impact as




 measured by a Trophic State Index. Total species richness showed similar patterns and lack of relationship to




 stressor measures. Treating "naturalized" (non-stocked) North American species as natives produced a




 pattern similar to that for total species richness.








The number of introduced species was a useful metric in Great Lakes littoral areas (Minns et al. 1994).  In




SNE all, except three, lakes had between  1 and 6 non-native species (Figure 4a), generally increasing with




lake size (^=0.32 p=0.0001). Residual scores plotted against TP showed a lack of pattern with increased




stress, except that several of the relatively low TP lakes with high residuals (more non-native species than

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 expected) were stocked with 1-3 salmonids (Figure 3b).  Non-native species residuals showed the expected




 pattern with watershed disturbance (Figure 3c); a number of lakes with high residual scores and intermediate




 watershed disturbance were stocked. Thus, the number of non-native species adjusted for lake size should be




 a useful metric.









 Most other species richness and composition metrics used in other IBIs did not appear to be applicable in




 SNE.  There were only two rarely collected darters (and no sculpins) (Table 2). Likewise, there were only




 two suckers, with the creek chubsucker collected only once. Cyprinid species richness was somewhat higher;




 however 4 of 5 native minnows were uncommonly collected.  Golden shiner was widespread (72% of




 sampled SNE lakes) and is tolerant of degraded conditions. Only 8 of the 55 sampled lakes had native




 cyprinids other than golden shiner; six of these had only one other minnow. Native minnow species richness




 may be a useful metric, but it would be  essentially a binary metric.  Of the three native sunfish in SNE (Table




 2), pumpkinseed was ubiquitous (91 % of sampled lakes). The other two sunfish were uncommon and were




 not collected in the same lakes, preferring very different habitats. Therefore a native sunfish metric contained




 very little information.









 Atlantic salmon and fathead minnow  were the only SNE lake fish rated intolerant of anthropogenic stress in




 Northeast lakes by Whittier and Hughes (in review). Lowering the threshold to tolerance scores of 11 (of 16)




 added 13 uncommon species (11 of these were collected in only 1 or 2 lakes each; Table 2). Only five lakes




 had more than one species from the expanded list of intolerants and most had none. There was a very weak




 relationship between lake size and intolerant species (^=0.14, p=0,0045). Maximum intolerant species




 (uncorrected for lake size) tended to decrease with increased TP, most lakes with intolerant species >0 had




moderate to low watershed disturbance.  Thus, this metric may be useful, although most lakes  would  get the




minimum metric score.

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 One of the features of the original sucker species metric was their longevity, providing a "muJtiyear




 integrative perspective" (Karr et al. 1986). To address the large-bodied, long-lived component of lake fish




 assemblages, I selected five relatively large native species to comprise an analogous metric. There was a




 significant, but weak, relationship between large species richness and lake size (^=0.19, p=0.009; Figure 5a).




 There was little association between increased TP and fewer large native species (Figure 5b). Both the




 regression residuals (Figure 5c) and the raw species counts tended to decrease with increased watershed




 disturbance.  The four lakes circled in the lower left of Figure 5c are subject to manipulations (e.g.,




 reclamation,  draining) which are not detected by either stressor measures.  This appears to be a useful metric.




 A similar analysis using 10 native small species (4 minnows, 2 sunfish, 2 darters, and killifish) showed no




 associations with any of the stressor measures.









 Perhaps the most frequently replaced metric is % green sunfish (Simon and Lyons 1995). In SNE, % bluegill




 would be the  most likely candidate. Bluegill is not native and sometimes dominated the assemblages, being




 most abundant in CT and RI, becoming less dominant in MA and being replaced by yellow perch as a




 dominant in NH.  It occurred in only two NHE lakes. In the NCZ ecoregion where it was most widespread, %




 bluegill was not associated with higher stressor measures. A variant metric might be %  individuals of the




 most abundant non-native species (often bluegill). This did not improve the metric performance. Somewhat




 better was the proportion of individuals of all non-native species (or conversely proportion of native




 individuals).  This metric showed no lake size effect, and no relationship with TP (Figure 6a). However, there




was a tendency  for the % non-native individuals to increase with watershed stress. Most of the lakes in the




upper left of Figure 6b had small watersheds and  were probably more stressed than indicated by the




watershed analysis. This metric is probably useful.

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 There were nine tolerant species collected (Table 2). Eleven of the 12 smallest lakes had >90% tolerant




 individuals (Figure 7a). Pumpkinseed were fairly abundant in many of these ponds. Removing pumpkinseed




 from this metric had the greatest effect in smaller lakes. There was a clear association between  % tolerants




 and TP. With pumpkinseed included, all eutrophic and hypereutrophic lakes (except one) had >80% tolerant




 individual (Figure 7b). The pattern was less dramatic with pumpkinseed removed (Figure 7d).  For watershed




 disturbance, the pattern of increasing proportion of tolerant individuals with increasing stress was stronger




 with pumpkinseed removed (Figure 7c & e).









 TROPHIC COMPOSITION METRICS




 As with the species richness metrics, the  trophic composition metrics were problematic in SNE lakes. For




 example, chain pickerel and American eel were the only native top carnivores (Table 2). Other natives such




 as yellow perch, white perch and brook trout are piscivorous as large adults. However, white perch is native




 in only about a third of the SNE lakes and tolerant of stressed conditions. Brook trout is native to SNE




 streams, but is nearly always maintained by stocking in lakes.  The most widespread top carnivore was the




 non-native largemouth bass (in 50 of 55 sampled lakes) which was often found in quite degraded lakes, as




 was black crappie. I selected eight species that are strongly piscivorous and not highly tolerant of stressed




 conditions (Table 2). I also examined this metric with largemouth bass included.  Any species maintained by




 stocking was not included for that lake, which effectively eliminated Atlantic salmon and lake trout.









 For the restricted species list (excluding largemouth bass), there was a slight tendency for % top carnivores to




 increase with lake size. The highest scores occurred in the lakes with TP < 20 and low to moderate watershed




disturbance (Figure 8a-b). The one outlier lake had 19% of individuals as rock bass; removing rock bass




would still leave this lake with one of the  highest % top carnivores scores. Including largemouth bass tended




to decrease the resolution of this metric (Figure 8c-d). That is, the peaks of the scatter plots moved to the

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                                                                                      Whittier   15




 right on the stressor plots, and the range of scores approximately doubled. There is concern that removing a




 highly tolerant species changes the metric from a trophic guild metric into a tolerance metric. I believe that




 the original intent of the metric is maintained with the reduced list.









 A % insectivorous individuals metric also required some adjustments. Only seven uncommonly collected




 species meet the strict definitions of insectivory of Halliwell et al. (this book). I selected six additional native




 generalist feeder species that tend toward the insectivorous end of the trophic spectrum, and which are not




 highly tolerant of degraded conditions (Table 2).  With this species list % insectivorous individuals scores




 related very well to TP and watershed disturbance (Figure 9b-c). The three outlier lakes in the upper right of




 the watershed disturbance plot all had yellow perch as the most abundant species. Also problematic for this




 metric was that 11 of 12 smallest lakes had <10% insectivores (Figure 9a). Eight of these small lakes  had




 pumpkinseed as a dominant species. Adding pumpkinseed to the insectivore species list for small lakes




 removed the size effect, but did not improve the relationship with the stressor measures.









 There are few true omnivore species (with a substantial portion of their diet including plant material) in the




 Northeast (Halliwell et al. this book), but a fairly large number of generalist feeder species (feeding at several




 trophic levels rather than primarily from one trophic level [Minns et al. 1994]).  I selected 10 species for a




 generalist feeder metric (Table 2). The maximum scores for % generalist feeder individuals decreased  with




 lake sizes greater than about 30 ha (Figure lOa).  Most of the small lakes had high scores due generally to




dominance by bluegill and pumpkinseed. The lowest scores (< 30%) were all in relatively low productivity




lakes (TP < 20).  The highest scores tended to be in lakes with moderate levels of stress (Figure lOb-c).

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                                           DISCUSSION









 Seven of the candidate metrics appear to be successful and should provide a framework for future refinement




 of lake metrics and development of an ffil for inland lakes in southern New England.  Two are species




 richness metrics, non-native species richness adjusted for lake size as a negative metric, and large species




 richness (which may not need to be adjusted for lake size) as a positive metric. The % non-native individuals




 and % tolerant individuals metrics could be considered in the richness and composition category (Karr et al




 1986) or in the indicator species category of Simon and Lyons (1995) as negative metrics.  Minns et al.




 (1994) placed the former metric in the abundance and condition category.  It may be possible to develop an




 intolerant species metric, or a small species metric. With judicious selection of species, all three trophic




 composition metrics appear to be useful.









 The results presented here also illustrate some of the conceptual and ecological issues important for assessing




 biotic integrity of inland lakes, and differences between lotic and lentic fish assemblages.  Lakes in New




 England are naturally species depauperate (Schmidt 1986). In this way they are somewhat analogous to




 coldwater streams, where increased total species richness is usually an indication of degradation (Lyons et al.




 1996).  In New England lakes, the source of additional species is introductions, rather than immigration from




 warmwater streams. The relationship between native species richness and introductions is complex for SNE




 lakes.  Moyle and Light (1996) proposed that most successful invasions occur without loss of native species




 and that non-native predators should have greater effect on native assemblages than non-predators. A




 substantial proportion of non-native species in SNE are predators. For the Northeast as a whole, Whittier et




 al. (1997a) demonstrated an association between increased predator richness (usually from non-natives) and




 lower minnow richness. However, preliminary analyses could not demonstrate an overall decrease in native




species richness with increased numbers of non-natives species (T. Whittier unpub. data). Thus, in SNE

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 there appears to adequate ecological "space" for the additional non-native species in general, but some




 portions of the native assemblage may have been extirpated.  It probably cannot be known whether SNE lakes




 had more minnow species prior to introduction of additional littoral predators.









 A third rule for species invasion (Moyle and Light 1996) was that increased invasion success occurs when




 native assemblages are depleted or disrupted.  The greater introduced species richness, and higher proportion




 of non-native individuals in more stressed lakes support this idea. However, it appears that these stress levels




 have not generally been high enough to eliminate native species, because native species richness showed no




 association with anthropogenic stress.








 Fish species tolerance of, or sensitivity to degraded lake conditions appear to differ from their tolerances to




 impaired lotic systems. When I used species tolerance classifications from stream IBIs the proportion of




 tolerant individuals was lowest in the most stressed lakes (T. Whittier unpub. data).  This led Whittier and




 Hughes (in review) to evaluate individual species tolerances to five stressor measures in Northeast lakes, and




 assign new tolerance ratings. Applying these revised classes to the SNE assemblage data generally produced




 the expected associations with  stressor measures, except in the smallest lakes and ponds (g 10 ha). These




 results, coupled with the larger species pool for lotic fish compared with lentic fishes, pose some interesting




 questions relative to how lake ecosystems stress fish compared stream ecosystems, and whether there are any




 truly intolerant warmwater lake species.









The trophic composition metrics presented a number of interesting challenges, in addition to the guild




membership issues (e.g., lack of objective criteria, dietary plasticity and changes with age) discussed by




Minns et al.  (1994). In SNE lakes, a number of species with obvious trophic guild membership react to




degraded conditions in the opposite manner to what the metric should indicate.  The clearest examples are the

-------
                                                                                     Whittier   18


 piscivores. For most of SNE chain pickerel and American eel are the only native top carnivores. Largemouth


 bass is clearly a top carnivore, but is tolerant of degraded lake conditions. Black crappie and white perch are


 usually placed in the piscivore guild, but are two of the most tolerant species in SNE lakes (Whittier and


 Hughes in review), and among the dominant species in many stressed lakes.  Finally, 16 of 40 species


 collected by EMAP in SNE lakes could be considered as piscivores (Halliwell et al. this book), producing


 very high % piscivorous individuals scores (40 -100%  for more than half of the lakes). In selecting species


 for this metric, I did not try to choose the most sensitive piscivores, but limited the list to the most


 carnivorous species that were also not highly tolerant, regardless of the native status. This produced metric


 values in the 0 -10% range and the expected association between the metric and stressor scores. Similar


 adjustments were needed for the other two  trophic composition metrics.
                                                                                  i



 Additional work is needed  in a number of areas. First,  biomass data may have the potential to improve all of


 the trophic guild metrics, and provide additional abundance and condition metrics (Minns et al. 1994).


 However EMAP, which was not primarily a fisheries survey, did not collect those data. Second, some


 standard unit of sampling effort needs to be established. Multiple gear sampling makes that a complex


 problem. A sampling scheme combining electrofishing and gill nets may provide abundance data with lower


 variability. Third, additional work on lake classification schemes is needed.  Even within a relatively


homogenous area like southern New England there are  questions about whether lakes in the Northeast


Coastal Zone ecoregion should be held to be same standard as those in the Northeast Highlands-ecoregion.


Finally, work is needed to develop metric scoring and an overall ffil, and to validate both the metrics and the


index with additional data.

-------
                                                                                Whittier   19




                                    ACKNOWLEDGMENTS









 I thank Bob Hughes, Dave Halliwell and Bob Daniels for numerous insightful discussions of these issues.




 Martin Jennings, Melissa Drake, Dave Peck, and Bob Hughes provided useful reviews of an earlier draft.




 This research was supported by the U.S. Environmental Protection Agency through Contract Number 68-C5-




 0005 to Dynamac International, Inc.









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-------
                                                                                    Whittier    20




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                                                                                     Whittier   21




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                                                                                   Wh




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                                                                                    Whittier   26




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-------
                                                                               Wr
Table 1. Principal components analysis of watershed-level human influence measures: three Ian
variables (% forest, % urban, % agricultural), human population density(#/km2), and road densi
variables except % forest were Iogi0(x+l) transformed. The first Principal Component (PCA-T
generalized human influence.
Principal
Component
PC-1
PC-2


% Forests
% Urban
% Agricultural
Population Density
Road density
Eigenvalue

3.09
0.88
Eigenvectors
PCA-1
-0.42
0.49
0.32
0.52
0.46
Proportion of Ct
Variance
0.62
0.17

PCA-2
0.34
0.31
-0.81
0.21
0.30

-------
                                                                                Whittier   28
 Table 2. Fish species native status, tolerance ranks and trophic guild as used in this
 study, collected at 55 southern New England lakes by EMAP during summers  1991-94.
 Tolerance rating scores from Whitlier & Hughes (in review) range 4-16, I=Intolerant,
 MI=Moderately Intolerant, M=Moderate, MT=Moderately Tolerant, T=ToleranL For
 Trophic Guild: TC=Top Carnivore, GF=GeneraIist Feeder, IN=Insectivore.
 Species
              # of Lakes
# of Lakes   as Introduced or   Tolerance    Trophic
as Natives       Stocked         Rating       Guild
 American eel
 Anguilla rostrata
 alewife
 Alosa pseudoharengus
 gizzard shad
 Dorosoma cepedianum
 common carp
 Cyprinus carpio
 common shiner
 Luxilus cornutus
 golden shiner
 Notemigonus crysoleucas
 bridle shiner
 Notropis bifrenatus
 spottail shiner
 N, hudsonius
 fathead minnow
 Pimephales promelas
 creek chub
 Semotilus atromaculatus
fallfish
S. corporalis
    8
   37
9/M
                               10/M
                                5/T
                               12/M
5/T
                               13/MI
                               14/MI
                                15/1
                               12/M
                               11/M
TC
            GF
            IN
GF
            IN
            IN
            GF
            IN
            IN

-------
Table 2. (continued)
                                            # of Lakes
Species
white sucker
Catostomus commersoni
creek chubsucker
Erimyzon oblongus
white catfish
Ameiurus catus
yellow bullhead
A. natalis
brown bullhead
A. nebulosus
channel catfish
Ictalurus punctatus
tadpole madtom
Noturus gyrinus
northern pike
Esox lucius
chain pickerel
E. niger
rainbow smelt
Osmerus mordax
rainbow trout
Oncorhynchus tnykiss
Atlantic salmon
Salmo solar
brown trout
5. trutta
# of Lakes as Introduced or Tolerance Tropl
as Natives Stocked Rating Guil
23 8/MT GF

1 9/M IN

2 »/M

20 6/MT GF

42 5/T GF

2 --/M

1 , -Ml IN

3 10/M TC

34 7/M TC

2 11/M GF

7 --/MI

1 15/1 TC'

3 --/M


-------
                                                                               Whittier   30
 Table 2. (continued)
 Species
              # of Lakes
# of Lakes   as Introduced or   Tolerance
                            as Natives
               Stocked
Rating
Trophic
 Guild
 brook trout
 Salvelinus fontinalis
 lake trout
 S. namaycush
 banded killifish
 Fundulus diaphanus
 mummichog
 F. heteroclitus
 white perch
 Morone americana
 rock bass
 Ambloplites rupestris
 banded sunfish
 Enneacanthus obesus
 redbreast sunfish
 Lepomis auritus
 pumpkinseed
 L, gibbosus
 bluegill
 L. macrochirus
 smallmouth bass
Micropterus dolomieu
 largemouth bass
M. salmoides
black crappie
Pomoxis nigromaculatus
   11
   50
                 35
                 15
                 50
                 21
                               13/MI
                               14/MI
 10/M
                               -IT
                               5/T
                               12/M
                               9/M
                               10/M
 4/T
 4/T
10/M
 5/r
            TC*
  IN
             GF
            TC
             IN
             IN
  GF
 GF
 TC

-------
Table 2, (continued)
Species
              # of Lakes
# of Lakes   as Introduced or   Tolerance    Trophic
as Natives       Stocked         Rating       Guild
swamp darter
Ethesotoma Jusiforme
tesselated darter
E, olmstedi
yellow perch
Percaflavescens
   44
                                            IN
                               11/M
6/MT
IN

-------
                                                                                      Whittier   32




 Figure Captions




 Figure 1. Locations of the 55 lakes sampled by the Environmental Monitoring and Assessment Program




 (EMAP) in southern New England during the summers of 1991-94.









 Figure 2. Relationship between sampled southern New England lake surface areas and two stressor




 measures: total phosphorus (ug/L), and watershed disturbance (1st axis PCA scores for % forest, % urban, %




 agricultural landuses, road density and human population density), plotted by ecoregions (a & c: solid circles




 = Northeast Highlands ecoregion, open circles = Northeast Coastal Zone ecoregion), and lake type (b & d:




 solid circles = named Reservoirs, open circles = named Ponds or Lakes).









 Figure 3. Native Species Richness, (a) Number of native species by lake size, (b) Residuals of the native




 species by lake size regression plotted against total phosphorus,  c) Residuals plotted against watershed




 disturbance PCA axis 1 (higher axis 1 value = increased human activity in the watershed).









 Figure 4. Non-Native Species Richness, (a) Number of non-native species by lake size,  (b) Residuals of the




 non-native species by lake size regression plotted against total phosphorus,  c) Residuals plotted against




 watershed disturbance PCA axis 1 (higher axis 1 value = increased human activity in the watershed).









Figure 5. Native Large Species Richness,  (a) Number of native large species by lake size,  (b) Residuals of




the native large species by lake size regression plotted against Total Phosphorus,  c) Residuals plotted againsi




watershed disturbance PCA axis 1 (higher axis 1 value = increased human activity in the watershed).

-------
 Figure 6.  Percent of individuals of non-native species. (a) % non-native individuals b




 % non-native individuals by watershed disturbance PCA axis 1 (higher axis 1 value = i




 activity in the watershed).









 Figure 7. Percent of individuals of tolerant species (a) % tolerant individuals by lake size




 pumpkinseed.  (b) % tolerant individuals by total phosphorus, including pumpkinseed. c




 individuals by watershed disturbance including pumpkinseed. d) % tolerant individuals I




 excluding pumpkinseed. e) % tolerant individuals by watershed disturbance excluding pt









 Figure 8. Percent of individuals of top carnivore species, (a)  % top carnivore individuals I




 excluding largemouth bass, (b) %  top carnivore individuals by watershed disturbance excli




 bass, c) % top carnivore individuals by total phosphorus, including largemouth bass, (d) 95




 individuals by watershed disturbance including largemouth bass.









 Figure 9.  Percent of individuals of insectivore species. (a) % insectivore individuals by Iak<




 insectivore individuals by total phosphorus, c) % insectivore individuals by watershed disti




 1 (higher axis 1 value = increased human activity in the watershed).









 Figure 10.  Percent of individuals of generalist feeder species. (a) % generalist feeder individ




size, (b) % generalist feeder individuals by total phosphorus,  c) % generalist feeder individu;




disturbance PCA axis I  (higher axis 1 value = increased human  activity in the watershed).

-------

-------
Southern New England Lakes
Total Phosphorus
120 -
,-J00 '".
3; 80 :
w :
o 6° :
Q. '.
§ 40 :
r-
o. :
20 :
0 :
1
o a 120 -
100 :
80:
,
60 :
o
o * :
40 :
• o o o ;
9 1 0 -
10 100 1000 1
b

0 °

o
0 °
o °
0 o o o
° 0 o *
m S» 0 ** Q W
• 9
10 100 1000
Lake Area (ha) Lake Area (ha)
• Northeastern Highlands * Named Reservoirs
o Northeastern Coastal Zone ° Named Lake/Pond
Watershed Disturbance
4 -
,- 3 -
Watershed PCA-'
O -* N)
i i i
-1 -
-2 -
o o ° C 4 -
o
00
o 3 -
o
0 0
n O f. ~
o° o 0
cP °° °. o o °
0 " ~ 1 "
0 0 °
* •
* •* 
-------
                            Native Species





CO

-------
                   Non-Native Species
10 -
8 -
(ft

-------
                Native Large Species
6 -


4 -
OT
CD
***•• ft
o *
CD


1 -
o -
1


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to 1 -
CO
3
"Ti n
.— 0 -
CD
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a


. *




* * MM m m mm m . * •

.. ... ...
... *M .
10 100 1000
Lake Area (ha)
Phosphorus
b
2 -
.
\^f . *
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• » o -
	 •• 	 • — »»-»* 	 	 	 	 — . u
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T 	 1 	 1 	 1 	 1 	 ] 	 1 	 . 	 1 	 1 	 1 	 1 	 1 	 1 	 1 	 1 	 1 	 1 	 1 	 1 	 1 	 1 	 , 	 1 	 1 	 1 -3

Species Lakes
Brown Bullhead 42

Chain Pickerel 34
\lit !•» 4 ^~ *^ C*t t *+ $* &+ &+ ^fc rt
White Sucker 23

American Eel 8
Creek Ghubsucker 1




Watershed Disturbance
c

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* .*
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 25
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125
-2
-1
1
Total Phosphorus (^g/L)
                             Watershed PCA Axis 1

-------
              % Non-Native Individuals
      Phosphorus
Watershed Disturbance
100 -

80 :
10
to :
l60-
>
E 40 •
^ -
20 -_
0 :

•
a
. % •
•
*• * * »
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Total Phosphorus (n9/L)
Watershed PCA Axis 1

-------
                     % Tolerant Individuals
1UU
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to
_to .c
ZJ Q. 60
"O C
lo «'
.2 20 -
O
c
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• • % •,
. • »* a
s •
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s • •
Species
Largemouth Bass
Pumpkinseed
Brown Bullhead
Golden Shiner
* • •* . * Bluegill
• * Black Crappie
• White Perch
• • * * * Common Carp
/ •
1 10 100 1000

Lake Area (ha)
Lakes
50
50
42
39
35
21
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3


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viduals
umpkinseed
O) 00 O
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ig 40;
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-------
Top Carnivores
50 -i

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'•&
10 -
0 -
70 -
65,
/
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"co
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.•* 10-
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, Largemouth Bass
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"1 — i — t 	 t 	 y 	 | 	 i — i — i — i — p— i — i — r — ! — j — i — r— r— i 	 |r"'i 	 j 	 i 	 i 	 | i ' ' * ' i l ' f * i ' ' ' ' i ' ' * * i * ' ! f i > ' ' • i f '
0 25 50 75 100 125 -2-101 234
Total Phosphorus
Watershed PCA Axis 1

-------
                                 Insectivores
13
•a
100
80
' 60
i
i
40 -

20 -
0 -
. • . a
»» •
*
Species
Yellow Perch
Banded Killifish
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                                                                  NHEERL-COR-2167A
x ' TECHNICAL REPORT DATA
(Please read instructions on the reverse before co,
1. REPORT NO.
EPA/600/A-97/089
2.
4. TITLE AND SUBTITLE
Development of IBI metrics for lakes in southern New England
7, AUTHOR(S) Thomas R. Whittier
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Dynamac International, Inc.
US EPA NHEERL
200 SW 35th Street
Corvallis, OR 97333
12. SPONSORING AGENCY NAME AND AC
US EPA ENVIRONMENTAL RESEX
200 SW 35th Street
Corvallis, OR 97333
3DRESS
kRCH LABORATORY

5. REPORT DATE
6. PERFORMING ORGANIZATION
CODE
8. PERFORMING ORGANIZATION REPORT
NO.
10. PROGRAM ELEMENT NO.
1 1 . CONTRACT/GRANT NO.
1 3. TYPE OF REPORT AND PERIOD
COVERED
14. SPONSORING AGENCY CODE
EPA/600/02
15. SUPPLEMENTARY NOTES:
1 6, Abstract:
In the early 1980's J.R. Karr and his colleagues developed the Index of Biotic Integrity (IBI) to assess the ecological
condition of fish assemblages in warmwater streams in the Midwest, as a biological tool to further the goals of the
Clean Water Act. The IBI has been repeatedly modified for other assemblages, regions and ecosystems, with varying
degrees of success. However to date, there has been only limited effort toward developing IBIs for inland lakes. The
development of lake IBIs lags behind that for warmwater streams due in part to the increased complexity in the scope
of assessment and sampling issues in lakes. In addition, streams tend to be managed, or under the authority of state
departments of environmental quality which are concerned with issues defined by the Clean Water Act. These
agencies have been shifting their regulatory emphasis to the biological condition of streams. Lakes, on the other hand
tend to be managed by state fish and game departments whose mandates emphasize management for fishability, not
biotic integrity. Finally, a number of ecological factors are less well understood for lake fish assemblages.
This manuscript evaluates the performance of numerous candidate metrics for lake fish assemblages in southern New
England, comparing metric behavior with total phosphorus {as a measure of eutrophication stress) and a generalized
measure of human activity in the watersheds (% of land in urban and agriculture, road and population density). This
manuscript presents solutions to issues of species tolerances to stressors in lakes and to trophic guild membership.
These modifications improved the performance of four candidate metrics (% individuals of highly tolerant species, %
top carnivore individuals, % insectivorous individuals, % generalist feeder individuals). A total of seven metrics appear
to be useful for evaluating biotic integrity of lakes in southern New England,
17.
a. DESCRIPTORS
New England, lakes, metric
development, index of biotic integrity
18, DISTRIBUTION STATEMENT
KEY WORDS AND DOCUMENT ANALYSIS
b. IDENTIFIERS/OPEN ENDED
TERMS

19. SECURITY CLASS (This Report)
20. SECURITY CLASS (This page)
c. COSATI Field/Group

21. NO. OF PAGES: 43
22. PRICE
EPA Form 2220-1 (Rev. 4-77)   PREVIOUS EDITION IS OBSOLETE

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