Marten A. Koops

Recovery Potential Assessment for Lake Sturgeon in Canadian Designatable Units

Abstract Significant declines in the abundance of lake sturgeon Acipenser fulvescens across most of its North American range have led to abundances less than 10% of estimated minimum sustainable population sizes and, in some locations, less than 1% of historic abundances. These precipitous declines in abundance have resulted in most lake sturgeon populations being considered a conservation concern and have prompted management actions toward recovery. Here we present modeling in support of a recovery potential assessment, using stage-structured matrix models and population viability analysis to quantitatively assess allowable harm, recovery efforts, probabilities of recovery, and recovery time frames. From this assessment, we conclude that lake sturgeon populations are most sensitive to harm on adult survival and that some designatable units are highly sensitive to any level of harm. However, the scope for recovering lake sturgeon by improving adult survival is limited; instead, larger proportional increas...

Distribution and ecology of Hemimysis anomala, the latest invader of the Great Lakes basin.

Since 2006, the known distribution of Hemimysis anomala has greatly expanded in the Great Lakes ecosystem, with, to date, 45 sites of occurrence among 91 monitored sites, located in four of the Great Lakes and the upper St. Lawrence River. By means of carbon and nitrogen stable isotopes, a first assessment of the feeding ecology of Hemimysis was completed. The δ13C values of 18 individuals collected in Lake Erie (Port Mainland) on a single date (Sept. 23, 2008) ranged from −30.2 to −24.5‰, indicating that Hemimysis could feed on multiple carbon sources including pelagic and littoral autochthonous and terrestrial carbon. In Lake Erie, variation in δ13C was related to δ15N, indicating the importance of food source for determining the trophic position of Hemimysis. The δ15N signatures of individuals were strongly related to their C/N ratios, suggesting that variations in the nutritional value of Hemimysis may depend on trophic position. Isotopic variation among individuals in Lake Erie was complemented by temporal variation in Lake Ontario. Monthly changes (from June to December 2008) in carbon isotope signatures were observed and related to changes in water temperature, highlighting the variations in the baseline prey signatures that fuel Hemimysis diets. The observed variation in stable isotope signatures occurring among individuals within a localized Hemimysis assemblage and temporally should be considered as a key design feature in further studies attempting to identify the possible effects of Hemimysis on nearshore food webs in the Great Lakes.

Invasion dynamics of round goby (Neogobius melanostomus) in Hamilton Harbour, Lake Ontario

Most introduced non-native species fail to establish as a result of mortality or reproductive failure. An established population can increase the probability of survival and reproductive success of newly introduced individuals by reducing both Allee effects and demographic stochasticity. Previously, attention has been paid to the establishment phase of the invasion process and its probability modelled as a stochastic process, while the spread phase has received less attention. By analyzing data collected during the spread phase of an invasion of the round goby, Neogobius melanostomus, in Hamilton Harbour, Lake Ontario, we develop an analytical approach to backcalculate the time to establishment and to determine the time to habitat saturation. Our modelling shows that: (1) during the transition between arrival and establishment, propagule pressure in the form of new adults entering the area can be very low and still represent a significant probability of establishment; (2) much higher concentrations of juveniles would be needed to pose a significant risk of invasion; (3) the demographic contribution of propagule pressure during the spread phase is low and its total elimination will not halt population growth and spread; (4) a short elapsed time between arrival and establishment indicated that the transition between these two phases can be characterized as a deterministic process with high propagule pressure and low adult mortality rates; and, (5) very aggressive management actions would be needed to halt population growth after population establishment, suggesting that preventative measures are the most effective management options available to reduce risk of future invasions.

A synthesis of the ecological processes influencing variation in life history and movement patterns of American eel: towards a global assessment

American eel, Anguilla rostrata, is a catadromous fish that spawns in the Sargasso Sea and migrates to coastal waters and freshwater systems ranging from Greenland down the Atlantic coast to South America and has been regarded as comprising a panmictic population. American eel is in decline across much of its range. Research and management is primarily conducted at local to regional scales, yielding inconsistent research results and management recommendations that may be inhibited by large-scale processes. We review the research on American eel ecology demonstrating that its variable life history and movement patterns can be explained based on: (1) latitudinal productivity gradients; (2) ideal free habitat selection; (3) conditional evolutionarily stable life history strategies; (4) size at arrival to the coast (correlated with distance from the spawning grounds); and, (5) temperature variance and annual degree-day effects on somatic growth. Using these ecological processes, we outline how local and large-scale effects on American eel dynamics can be integrated in a panmictic (or quasi-panmictic) modelling framework to enable defensible predictions of population responses to anthropogenic and oceanic phenomena. Due to its widespread distribution and existing knowledge gaps, the conservation and management of American eel will require international cooperation.

Estimating establishment probabilities of Cladocera introduced at low density: an evaluation of the proposed ballast water discharge standards.

The International Maritime Organization has proposed ballast water discharge standards to reduce densities of taxa transported in ballast water. While reduced propagule pressure will almost certainly lower the risk of species introductions, we ask if the proposed standards will be effective against taxa capable of rapid population growth from small inocula, such as parthenogenetic taxa. We modified a diffusion approximation to calculate establishment probabilities as the probability of reaching a critical threshold density necessary to initiate sexual reproduction (and production of diapausing eggs for long-term persistence) before the onset of adverse environmental conditions. We parameterize our model for six Cladocera using growth rates measured during enclosure experiments conducted under favourable environmental conditions (i.e., using a precautionary approach). We then examine predicted establishment probabilities at different inoculum densities to determine the efficacy of the proposed ballast wate...

Measures of Larval Lake Whitefish Length and Abundance as Early Predictors of Year-Class Strength in Lake Michigan

ABSTRACT Many lake whitefish stocks in Lake Michigan have experienced substantial declines in growth and condition since the 1990s. Reduced growth and condition could result in reduced quality or quantity of eggs produced by spawning females, which in turn could negatively impact recruitment. We evaluated the potential for reduced recruitment by measuring early life stage density and length, and we discuss the utility of these measures as early indicators of lake whitefish year-class strength. Overall, mean larval density (number per 1000 m3 ± SE) in Lake Michigan was greater in 2006 (373.7 ± 28.3) than in 2005 (16.6±24.8); whereas, mean length (mm±SE) of larval lake whitefish was smaller in 2006 (12.87±0.07) than in 2005 (14.38± 0.13). The ratio of Zooplankton to fish density did not show an expected relationship with larval fish density or length. Rather, variation in larval density was best explained by a multiple-regression model that included larval length, spring wind intensity, and adult stock density as predictor variables. Our results suggest that the density of larval lake whitefish is not directly regulated by temperature or Zooplankton density at the time of emergence, but that a potential for density-dependent regulation exists when larval emergence rates are high. We conclude that the observed declines in growth and condition of adult lake whitefish are not resulting in substantial reductions in recruitment.

The Science Framework for Implementing the Fisheries Protection Provisions of Canada's Fisheries Act

In 2012, Canadas Fisheries Act was amended. New fisheries protection provisions provide for the sustainability and ongoing productivity of commercial, recreational, and Aboriginal fisheries. These provisions replace previous provisions that focused on fish habitats, and concerns have been expressed that the amended Act has lowered aquatic habitat protection. The science framework developed for implementation of the new provisions is based on the relationships between fisheries productivity and the response of habitats or populations to pressures, with pressures linked to specific classes of activities through pathways of effects models. The framework includes guidance on quantifying productivity, scales and types of impacts, establishing equivalence in offsetting, and managing risk. Risk of failing to achieve the intent of the fisheries protection provisions is only managed when impacts of activities have a net neutral or positive effect on fisheries productivity. This standard applies whether the evalua...

Long-term ecosystem studies in the Bay of Quinte, Lake Ontario, 1972–2008: A prospectus

Project Quinte can best be described as a long-term ecosystem study of the Bay of Quinte, Lake Ontario. Starting in 1972, Project Quinte was initially established to study the whole ecosystem effects of controlling phosphorus loadings in a eutrophic ecosystem. Since then, the Bay of Quinte ecosystem has experienced reduced nutrient loads, climatic events that changed the dominance of fish species, multiple invasions by non-native species, a resurgence of macrophytes, and increasing annual temperatures. Through this, the Bay of Quinte has gone from a study site to a Great Lakes Area of Concern to now the prospect of being delisted. The data that Project Quinte has assembled since its inception represents a unique opportunity to examine how ecosystems function, and the papers presented in this special issue provide evidence of the scientific and management benefits of careful long-term monitoring of ecosystem structures and processes.

Does Condition of Lake Whitefish Spawners Affect Physiological Condition of Juveniles

ABSTRACT Recent declines in growth and condition of several Great Lakes lake whitefish populations have raised concerns over potential impacts on juvenile physiological condition and ultimately recruitment. To test whether the condition of spawning adults influences juvenile condition via energy allocation dynamics, we partitioned the variation in age 0 juvenile physiological condition (i.e., growth in length and weight, whole-body moisture content, energy density, and protein content) among adult male and female (i.e., body condition, muscle moisture content, energy density, and protein content) and egg (i.e., wet and dry weight, moisture content, energy density, energy content per egg, and protein content) effects using redundancy analysis. Overall, a model that included sampling site, female condition, and egg quality explained 39% of the variation in juvenile physiological condition. After partitioning out the effects of females and eggs, site explained the most variation (23%). When other factors were accounted for, neither females (1.4%) nor eggs (2.7%) explained much variation in juvenile physiological condition. Of the variables studied, female muscle energy density, muscle moisture content, and egg moisture content were most closely associated with juvenile physiological condition. Our results suggest that parental effects, such as size, age, body condition, or body composition, may not be as important as extrinsic site-related effects or density-dependent effects in determining juvenile physiological condition.

Lake Ontario water quality during the 2003 and 2008 intensive field years and comparison with long-term trends

Phosphorus loading declined between the 1970s and the 1990s, leading to oligotrophication of the offshore waters of Lake Ontario during that time period. Using lake-wide data from the intensive field years of 2003 and 2008 and from available long-term data sets on several trophic state indicators (total phosphorus [TP], soluble reactive silica [SRSi], chlorophyll a and Secchi disc transparency [SDT]), we tested the hypothesis that oligotrophication of the offshore waters of Lake Ontario has continued in the 2000s. Significant differences between 2003 and 2008 include higher spring (April) TP, SRSi, and SDT in 2008, lower summer (July–August) SDT in 2008, higher summer chlorophyll a in 2008, and lower fall (September) TP, SRSi, and chlorophyll a in 2008. The decline in SRSi from spring to summer was greater in 2008 than in 2003. Change point and regression analyses on the long-term data revealed no trend in spring TP since 1996, in summer chlorophyll a since 1994, in spring SDT since 1998, in spring SRSi or SRSi decline from spring to summer since 1999, or in summer SDT since 2001. Neither the comparison of the 2003 and 2008 surveys nor the analysis of the long-term data supported our hypothesis of continued oligotrophication of the offshore of Lake Ontario in the 2000s.