Charles K. Minns, B.Sc., Ph.D.

Abstracts of recent publications

Abstracts available

Abstracts

Minns, C.K., Moore, J.E., Shuter, B.J., and Mandrak, N.E. 2008. A preliminary analysis of some key characteristics of Canadian lakes. Can. J. Fish. Aquat. Sci. 65:1763-1778.

Knowledge of Canada’s lakes is needed to manage environmental stresses. Lake inventory and lake feature databases were used to build a national impact assessment template and assess regional typology. There are ~910 400 lakes with area > 0.1 km2 (10 ha), 37% of the Earth’s total. Lake features (number of lakes by size class, maximum depth, mean:maximum depth ratio, Secchi depth, pH, and total dissolved solids) were modeled regionally by secondary watershed (SWS) using linear regression models. Lake trout (Salvelinus namaycush) occurrence was analyzed as a cofactor to highlight regional links between lake characteristics and aquatic biota. Significant (R2 from 0.231 to 0.492) regional models were obtained using area or maximum depth, lake trout occurrence, and their cross products as covariates. Analyses of fitted SWS coefficients showed that ecozones were a better predictor of lake characteristics than primary watersheds. The national typology was consistent with previous regional assessments. The regional models were used to estimate the number, area, and volume of lake trout lakes by size class and ecozone. There are ~66 500 lake trout lakes covering ~3 510 000 km2 primarily on Boreal and Taiga Shield areas. Regional lake resource models will enable national assessment of stresses such as climate change and invasive species.

Chu, C., Jones, N.E., Mandrak, N.E., Piggott, A.R. and Minns, C.K. 2008. The influence of air temperature, groundwater discharge and climate change on the thermal diversity of stream fishes in southern Ontario watersheds. Can. J. Fish. Aquat. Sci. 65:297-308.

The availability of suitable thermal habitat for fishes in streams is influenced by several factors, including flow, channel morphology, riparian vegetation, and land use. This study examined the influence of air temperature and groundwater discharge, predictors of stream temperature, on the thermal diversity (cold-, cool-, and warm-water preferences) of stream fish communities in southern Ontario watersheds. Site-level fish sampling data were used to assess the thermal diversity of 43 quaternary watersheds using three metrics, the proportion of sites within a watershed having (i) cold-, (ii) cool-, and (iii) warm-water fishes. Our results indicated that 53.9% of the variances in cold-water and 54.1% of the variances in warm-water fish distributions within the watersheds could be attributed to groundwater discharge and air temperature variables. Climate change scenarios suggested that watersheds with high groundwater discharge and the associated thermal diversity of fishes within those watersheds are less sensitive to climate change than watersheds with low groundwater discharge. Conservation of groundwater resources will be required to lessen climate change impacts on the thermal habitat and thermal diversity of stream fishes in southern Ontario watersheds.

Sharma, S., Jackson, D.A., Minns, C.K., and Shuter, B.J. 2007. Will northern fish populations be in hot water because of climate change? Global Change Biology 13:2052-2064 (doi: 10.1111/j.1365-2486.2007.01426.x)

Predicted increases in water temperature in response to climate change will have large implications for aquatic ecosystems, such as altering thermal habitat and potential range expansion of fish species. Warmwater fish species, such as smallmouth bass, Micropterus dolomieu, may have access to additional favourable thermal habitat under increased surface-water temperatures, thereby shifting the northern limit of the distribution of the species further north in Canada and potentially negatively impacting native fish communities. We assembled a database of summer surface-water temperatures for over 13 000 lakes across Canada. The database consists of lakes with a variety of physical, chemical and biological properties. We used general linear models to develop a nationwide maximum lake surface-water temperature model. The model was extended to predict surface-water temperatures suitable to smallmouth bass and under climatechange scenarios. Air temperature, latitude, longitude and sampling time were good predictors of present-day maximum surface-water temperature. We predicted lake surface- water temperatures for July 2100 using three climate-change scenarios. Water temperatures were predicted to increase by as much as 18C by 2100, with the greatest increase in northern Canada. Lakes with maximum surface-water temperatures suitable for smallmouth bass populations were spatially identified. Under several climate-change scenarios, we were able to identify lakes that will contain suitable thermal habitat and, therefore, are vulnerable to invasion by smallmouth bass in 2100. This included lakes in the Arctic that were predicted to have suitable thermal habitat by 2100.

Minns, C.K. 2006. Compensation ratios needed to offset timing effects of losses and gains and achieve no net loss of productive capacity of fish habitat. Can. J. Fish. Aquat. Sci. 63:1172-1182.

Minns’ (Can. J. Fish. Aquat. Sci. 54: 2463–2473 (1997)) framework for assessing net change of productive capacity of fish habitats in Canada is expanded to include the effect of timing of losses and gains on cumulative net change. The expansion requires establishment of a reference time frame for assessment. A time frame of twice the project’s duration is recommended. Delaying compensation actions while incurring losses early in a project increases the levels of compensation required. The addition of future discounting had much less effect on compensation requirements than the effects resulting from timing differences between losses and compensation. As discounts apply equally to losses and gains, they likely balance out over time. Delays between when habitat alterations occur and when expected productive capacity is attained increase the required compensation. There are advantages to starting compensation efforts early in a development project. A case study of a hypothetical northern diamond mine shows how various components of compensation (replacement, uncertainty, and timing) can be integrated when assessing net change. Consideration of all components of compensation indicates the need for tougher precautionary compensation guidelines with ratios greater than the current 1:1. Values of 2:1 or higher may be necessary to ensure attainment of Canada’s guiding policy principle of no net loss.

Minns, C.K. and Wichert, G.A. 2005. A framework for defining fish habitat domains in Lake Ontario and its drainage. J. Great Lakes Res. 31(Suppl.1):6-27.

Old and new paradigms for freshwater fish habitat science are examined and a framework for classifying habitat domains outlined in the Lake Ontario basin. The old paradigm emphasized static measures of both habitat and fish while the new one emphasizes dynamic process-oriented metrics. Temperature, light, and motion are the primary axes of the new paradigm and individual and population processes like growth, survival, and movement are the preferred fish metrics. The science that is contributing to the formation of the new paradigm is reviewed. Habitat domains with relatively homogeneous features are identified in lake and stream contexts and some of their patterns on Lake Ontario described. Human and other disturbances to those domains are explored. The correspondences between elements of the fish assemblage in Lake Ontario and the habitat domains are examined. Lotic and lentic examples of fish-habitat phenomena related to the new paradigm are presented. The paradigm shift has implications for scientific and management activities in the Great Lakes. The framework of habitat domains provides a basis for increasing our understanding of the role of habitat in fishery productivity as well as a basis for coordinating agency efforts to manage habitats for multiple use. There is a need to establish and maintain broad-based ecosystem monitoring programs to facilitate the use of habitat knowledge in decisionmaking, and to integrate fisheries management and fish habitat management within the responsible jurisdictions as a key step to implementing ecosystem-based management.

Chu, C., Mandrak, N.E., and Minns, C.K. 2005. Potential impacts of climate change on the distributions of several common and rare freshwater fishes in Canada. Diversity Distrib. 11:299-310.

Climate change will ultimately affect the supply and quality of freshwater lakes and rivers throughout the world. This study examines the potential impacts of climate change on freshwater fish distributions in Canada. Climate normals data (means from 1961 to 1990) from Environment Canada were used to map current climate found throughout the tertiary watersheds of Canada. Logistic regressions based on these climate data were used to develop predictive presence-absence equations for (a) common commercially and recreationally important species and (b) an Arctic freshwater species and a freshwater fish species of conservation significance listed by the Committee on the Status of Endangered Wildlife (COSEWIC). The Canadian Centre for Climate Modelling and Analysis Global Coupled Model 2(IS92a) provided forecasts of Canada’s climate in 2020 and 2050. The data from this scenario and the logistic regressions provided a ready framework for predicting the potential distributions of the fishes. Physical and ecological barriers would have to be overcome for the distribution of these species to actually change in response to climate change. Generally, coldwater species may be extirpated from much of their present range while cool and warmwater species may expand northward. Species that are limited to the most southern regions of the country may expand northwards. A conceptual framework for assessing potential climate change impacts on fishes and the variety of management strategies required to deal with these impacts are discussed. Our forecasts demonstrate the need for climate change assessments in species at risk as well as for common species.

Chu, C., C.K.Minns, J.E. Moore, and E.S. Millard. 2004. Impact of oligotrophication, temperature, and water levels on walleye habitat in the Bay of Quinte, Lake Ontario. Trans. Amer. Fish. Soc. 133:868-879.

Recent environmental changes in the Bay of Quinte, Lake Ontario, have coincided with a decline in the stocks of walleye Sander vitreus. Suitable habitat supply was estimated in three sections of the bay during the summers of 1972–2001 to assess its role in the decline. An empirical model was developed to predict suitable habitat area for walleyes based on their preferences for cool water and low light intensity. The results indicated that lack of suitable light limits walleye habitat in the bay. Walleye habitat in the shallow upper bay has decreased at the rate of 34 ha/year since the invasion of dreissenid mussels in 1994, while that in the middle and lower bays has remained abundant. Walleye stocks and suitable habitat in the upper bay have both declined since the early 1990s. However, this pattern has not been consistent through time and suggests that other factors have also affected the Bay of Quinte walleye population. The analyses developed here can be used as a tool to enhance the assessment of walleye habitat dynamics in the Bay of Quinte and allow us to examine the impact of oligotrophication on the habitat of an important recreational and commercial species.

Chu, C., C.K. Minns, and N.E. Mandrak. 2003. Comparative regional assessment of factors impacting freshwater fish biodiversity in Canada. Can. J. Fish. Aquat. Sci. 60:624-634.

This study presents a broad analysis of freshwater fish species biodiversity in relation to environmental and stress metrics throughout Canada. Species presence–absence data were used to calculate richness and rarity indices by tertiary watershed. Richness is higher in the southern parts of Canada, whereas rarity is concentrated in a “ring of rarity” around the periphery of the country. Environmental and stress indices were developed for each watershed using readily available mapped information. The environmental index was estimated using growing degree-days above 5°C, elevation range (m) within the watershed, mean annual sunshine hours, and mean annual vapour pressure (kPa). The number of crop farms, forestry, waste management, and petroleum refining facilities, road density (km·1000 km–2), dwelling density, and discharge sites (chimneys and laundry outlets) per 1000 km2 described the human stresses in each watershed. Conservation priority rankings were developed for the watersheds using an integrative index of the three indices. Watersheds in southern Ontario and British Columbia were ranked high because they contain the greatest biodiversity and the most stress. This study indicates how regional analyses can guide fisheries and watershed management.

Minns, C.K. and J.E. Moore. 2003. Assessment of net change of productive capacity of fish habitats: the role of uncertainty and complexity in decision-making. Can. J. Fish. Aquat. Sci. 60:100-116.

Canada’s fish habitat management is guided by the principle of “no net loss of the productive capacity of fish habitat” (NNL). Many development proposals are assessed using habitat information alone, rather than fish data. Because fish–habitat linkages are often obscured by uncertainty, uncertainty must be factored into NNL assessments. Using a quantitative framework for assessing NNL and lake habitats as a context, the implications of uncertainty for decision making are examined. The overall behaviour of a net change equation given uncertainty is explored using Monte Carlo simulation. Case studies from Great Lakes development projects are examined using interval analysis. The results indicate that uncertainty, even when large, can be incorporated into assessments. This has important implications for the habitat management based on NNL. First, schemas to specify relative levels of uncertainty using simple habitat classifications can support robust decision making. Second, attaining NNL requires greater emphasis on minimizing habitat loss and creating new areas to compensate for losses elsewhere and less on detailing small incremental changes in modified habitats where the fish response is difficult to demonstrate. Third, the moderate to high levels of uncertainty in fish–habitat linkages require that created compensation is at least twice the losses to reasonably ensure NNL.

Doka, S.E., D.K. McNicol, M.L. Mallory, I. Wong, C.K. Minns, N.D. Yan.2003. Assessing potential for recovery of biotic richness and indicator species due to changes in acidic deposition and lake pH in five areas of southeastern Canada. Environm. Monitoring and Assessment 88:53-101.

Biological damage to sensitive aquatic ecosystems is among the most recognisable, deleterious effects of acidic deposition. We compiled a large spatial database of over 2000 waterbodies across southeastern Canada from various federal, provincial and academic sources. Data for zooplankton, fish, macroinvertebrate (benthos) and loon species richness and occurrence were used to construct statistical models for lakes with varying pH, dissolved organic carbon content and lake size. pH changes, as described and predicted using the Integrated Assessment Model (Lam et al., 1998; Jeffries et al., 2000), were based on the range of emission reductions set forth in the Canada/US Air Quality Agreement (AQA). The scenarios tested include 1983, 1990, 1994 and 2010 sulphate deposition levels. Biotic models were developed for five regions in southeastern Canada (Algoma, Muskoka, and Sudbury, Ontario, southcentral Québec, and Kejimkujik, Nova Scotia) using regression tree, multiple linear regression and logistic regression analyses to make predictions about recovery after emission reductions. The analyses produced different indicator species in different regions, although some species showed consistent trends across regions. Generally, the greatest predicted recovery occurred during the final phase of emission reductions between 1994 and 2010 across all taxonomic groups and regions. The Ontario regions, on average, were predicted to recover to a greater extent than either southcentral Québec or the Kejimkujik area of Nova Scotia. Our results reconfirm that pH 5.5-6.0 is an important threshold below which damage to aquatic biota will remain a major local and regional environmental problem. This damage to biodiversity across trophic levels will persist well into the future if no further reductions in sulphate deposition are implemented.

Randall, R.G. and C.K. Minns. 2002. Comparison of a Habitat Productivity Index and an Index of Biotic Integrity for measuring the productive capacity of fish habitat in nearshore areas of the Great Lakes. Journal of Great Lakes Research 28(2): 240-255.

Habitat Productivity Index (HPI) and an Index of Biotic Integrity (IBI) were compared as measures of habitat productive capacity for fish assemblages in nearshore areas of Lake Erie and Lake Ontario. Forty-three species of fishes were captured by boat electrofishing at three areas with contrasting habitats-coastal wetlands, harbor breakwalls, and exposed shorelines. HPI and IBI were correlated among samples as expected, but HPI was most closely correlated with fish community biomass, whereas IBI was correlated with fish species richness. The HPI and IBI indices differed significantly among samples from the three habitat areas in both lakes, reflecting the differences in the abundance and composition of fish catches. The ranking of habitat productive capacity depended on the index: species richness and IBI were highest at the coastal wetlands, and biomass and HPI were highest at the harbors. Results support the contention that to effectively determine habitat productive capacity, both the production and diversity characteristics of the fish community need to be evaluated.

Morrison, H., C.K. Minns, and J.F. Koonce. 2001. A methodology for identifying and classifying aquatic biodiversity investment areas: Application in the Great Lakes basin. Aquat. Ecosystem Health and Managem. 4(1):1-12.

A scientifically defensible methodology for identifying areas of high biodiversity in aquatic environments is presented. Areas of high biodiversity or Aquatic Biodiversity Investment Areas are identified using a technique referred to as Habitat Supply Analysis. This technique uses the microhabitat features of an ecosystem in conjunction with information on the microhabitat preferences of fish to calculate the suitability of an area to fish. The method is structured so that the suitability of habitat to lifestages of fish, species of fish, groups of fish and fish assemblages can be evaluated. The methodology recognises that to some degree all areas within an aquatic system contribute to the maintenance of biodiversity. As such, a classification scheme is proposed to evaluate the potential versus the actual contribution of an area to the maintenance of biodiversity in an ecosystem. This classification scheme is designed to help prioritise habitat restoration and preservation efforts. Prototype evaluations of the methodology for identifying and classifying Aquatic Biodiversity Investment Areas are presented.

Minns, C.K. 2001. Science for freshwater fish and habitat management in Canada: current status. Aquatic Ecosystem Health and Management 4:423-436.

Canada’s diverse freshwaters support a rich biodiversity of more than 200 species. Canada has strong legislation capable of conserving and protecting freshwaters habitats. Fish are a key driver and indicator for restoration and conservation efforts. Many of Canada’s freshwater species in Canada are thought to be at risk. Apart species such as brook trout, lake trout, walleye, and yellow perch, the ecology and habitat requirements of most freshwater species are poorly known. Studies have mainly been descriptive and comparative but experimental, ecosystem-scale integration, and modelling activities are increasing. While science related to fish and their habitats is growing, little is focused on the links between the production and dynamics of fish populations and communities, and the supply and distribution of habitats at various scales. Habitat management is still mainly reactive, assessing development at the site-level with considerable uncertainty about the mitigation and compensation actions approved to offset habitat losses and modifications. Communication between science and management is improving. Canada has invested much energy on cumulative impact assessment but effective methods for tracking cumulative change and the interaction of multiple stresses have not emerged. Nonetheless there is a broad consensus on the need to take an ecosystem-based approach to sustainable use of Canada’s natural renewable resources, including freshwaters and their fish. Management needs to shift to a more proactive approach supported by better deployment of available science and scientific methods. Science should emphasize quantitative whole ecosystem studies of fish and habitat especially the development of models and experimental manipulations. If current trends of fish habitat loss are maintained in Canada, further declines in the quality and diversity of freshwater fish resources are certain despite our apparent natural wealth. Modest investments in securing the future of its freshwater fishery resources based on scientific advice may yet begin movement toward an ecologically sustainable future.