Pierre Pepin - Academia.edu (original) (raw)
Papers by Pierre Pepin
Journal of Experimental Biology
Species with a wide distribution can experience significant regional variation in environmental c... more Species with a wide distribution can experience significant regional variation in environmental conditions, to which they can acclimatize or adapt. Consequently, the geographic origin of an organism can influence its responses to environmental changes, and therefore its sensitivity to combined global change drivers. This study aimed at determining the physiological responses of the northern shrimp, Pandalus borealis, at different levels of biological organization and from four different geographic origins, exposed to elevated temperature and low pH to define its sensitivity to future ocean warming and acidification. Shrimp sampled within the northwest Atlantic were exposed for 30 days to combinations of three temperature (2, 6 or 10°C) and two pH levels (7.75 or 7.40). Survival, metabolic rates, whole-organism aerobic performance and cellular energetic capacity were assessed at the end of the exposure. Our results show that shrimp survival was negatively affected by temperature abov...
Fish and Fisheries
Environmental impacts on fisheries are pervasive, yet methods to account for them in stock assess... more Environmental impacts on fisheries are pervasive, yet methods to account for them in stock assessments and management decisions vary in rigour and quality. The prevalence and efficacy of methods to account for environmental impacts are not well documented, limiting our ability to adequately respond to future environmental and climate changes for adaptive resource management. In Canada, legislation now requires that environmental conditions are considered in the management of fish stocks, yet the current extent of implementation in assessment processes is poorly understood. We assessed the use of climate, oceanographic and ecological considerations in science advisory processes for 178 stock assessments by Fisheries and Oceans Canada. We evaluated whether these considerations were included in conceptual hypotheses about broad‐scale mechanisms, quantitative or qualitative analyses, and the development of management advice on current or future stock status. Conceptual hypotheses were i...
CM Documents - ICES, 2000
We present station-specific depth integrated abundance and biomass of Calanus spp. (stage-specifi... more We present station-specific depth integrated abundance and biomass of Calanus spp. (stage-specific abundance, CI-CVI, of C. finmarchicus, C. glacialis, C. hyperboreus and combined biomass of late stages, CIV-CVI, of Calanus spp.) collected from zooplankton monitoring programs from 19 subregions spanning the Newfoundland and Labrador Shelves, Gulf of St. Lawrence (GSL), Scotian Shelf, and Gulf of Maine (GoM). These data span years 1999-2016, except the southwest GSL subregion (1982-2016) and GoM (1977-2016). We also present data on near surface and bottom temperature and salinity from subregions in Canadian waters. We then present derived annual anomalies of abundance of the three species of Calanus, their combined biomass, and near surface and bottom temperature and salinity from all subregions. This is a contribution by Canadian and USA scientists and their institutions.Sampling and data processing methods are provided in detail in Sorochan et al. (2019), and zooplankton sampling m...
OCEANS 2017 – Anchorage, 2017
Studies investigating the impact of increasing ocean acidification on primary producers have been... more Studies investigating the impact of increasing ocean acidification on primary producers have been largely speculative and based on short-term experimental results. Few long-term studies are available to assess the rate of change in ocean acidity versus change in plankton populations. We utilize long-term observations and historical data based on a network of sites from the northwest Pacific, Arctic, and northwest Atlantic conducted by Fisheries and Oceans Canada to assess temporal change in ocean pH levels. We utilize both recent and long-term plankton data based on an ocean monitoring program initiated in the late 1990's and derived from the Continuous Plankton Recorder (CPR) Survey in the northwest Atlantic to assess interannual and decadal changes in acid-sensitive taxa back to the 1960's. We discuss these findings in light of the major uncertainties surrounding ocean acidification and how they will impact plankton in the marine ecosystem.
Biological oceanography, 2013
AbstractA simulation study of the influence of variations in food and predator abundance on growt... more AbstractA simulation study of the influence of variations in food and predator abundance on growth and survival of larval fish was conducted to determine whether changes in the abundance of either variable could be detected from analysis of size frequency data or from growth histories. The results indicate that estimates of the mean and variance in size frequency distribution would have to be very precise to detect changes in predator abundance. The mean and variance in individual growth rates appear to be useful tools to determine whether changes in predator or food abundance are influencing larval fish survival. As food abundance increases, the mean and variance in growth rates increase. However, as predator abundance increases, the variance in growth rates, for any given mean, decreases.
The MAPPS global database of photosynthesis-irradiance (P-E) parameters consists of over 5000 P-E... more The MAPPS global database of photosynthesis-irradiance (P-E) parameters consists of over 5000 P-E experiments that provides information on the spatio-temporal variability in the two P-E parameters (the assimilation number, and the initial slope) that are fundamental inputs for models of marine primary production that use chlorophyll as the state variable. The experiments were carried out by an international group of research scientists to examine the basin-scale variability in the photophysiological response of marine phytoplankton over a range of oceanic regimes (from the oligotrophic gyres to productive shelf systems) and covers several decades. These data can be used to improve the assignment of P-E parameters in the estimation of marine primary production using satellite data.
&... more <p>Located on a crossroads of some of the main currents associated to the Atlantic meridional overturning circulation (AMOC), Newfoundland and Labrador (NL) shelves are specially affected by changes in large-scale ocean circulation. Such circulation changes impact not only the regional climate, but also the overall water masses composition, with consequences on physical conditions, nutrient availability, oxygen content, pH, etc. Systematic hydrographic observations of this system have been carried out by Canada and other countries since 1948. The observational program was reinforced in 1999 with the creation of the Atlantic Zone Monitoring Program (AZMP), ensuring enhanced seasonal coverage and new biogeochemical observations. In 2014, this monitoring was augmented with the monitoring of ocean acidification parameters. Here we review historical physical-biogeochemical changes on the NL shelves, with an emphasis on low frequency variability and cycles. Results suggest, for example, that the cold intermediate layer (CIL), a cold mid-depth layer that is a key feature of the NL ecosystem, exhibited profound changes during the last 70 years. In the mid 60's, the CIL was anomalously warm compared to the rest of the time series. This warm period was followed by a cold period centered in the early 90's. Historical salinity records also suggest that fresher waters are found during warmer years, and vice-versa. Nitrate/Phosphate ratios suggest recent changes in water masses composition towards less Arctic waters flowing on the shelves. This is concurrent with a reduction in nutrients concentration on the NL shelves since about 2012, together with changes in the strength of the Labrador Current along the shelf.</p>
Other in Ices Annual Sciences Conference 23 09 Aberdeen Uk, 2005
Biological Oceanography, 1988
Journal of Fish Biology, 1989
Most studies on feeding‐related activities of fish in cold water (0° C) have not used eurythermal... more Most studies on feeding‐related activities of fish in cold water (0° C) have not used eurythermal species or examined a broad suite of activities. In this study we report on the feeding, growth, behaviour and conversion‐efficiency of 0 + Atlantic cod in response to water temperature and food availability. In one experiment, activity, opercular beat and growth decreased with decreasing temperature over the range 8·3–0·6° C. However, the conversion efficiency increased with decreasing temperature, a result partly explained by the relative change in activity and opercular rate. In another experiment, temperature had a linear effect on growth in cod fed different food rations. Both food availability and temperature were found to influence growth in group 0 + cod. The specific growth rate of cod in this experiment exceeded 2% day‐1. Growth data collected from cod sampled in the field during the cold‐water period showed a progressive increase of mean length over the season. Overall, these...
The Atlantic Zone …
... in Flemish Cap and Slope Waters Compared With the Adjacent Grand Banks Gary Maillet, Pierre P... more ... in Flemish Cap and Slope Waters Compared With the Adjacent Grand Banks Gary Maillet, Pierre Pepin, Joe Craig, Sandra Fraser and Dan ... mer compared to those observed on the GB Shelf (Table 1). The large difference in inventories during this seasonal transi-tion would ...
Canadian Journal of Fisheries and Aquatic Sciences, 1999
We investigated the effects of size-dependent encounter and susceptibility, the role of variation... more We investigated the effects of size-dependent encounter and susceptibility, the role of variation in the size distribution of predators, and the timing of prey-predator interaction during the larval phase in shaping the length frequency distribution of surviving fish larvae. These analyses based on general empirical size-dependent relationships may have broad implications in understanding larval fish cohort dynamics. We demonstrated that the formulations of encounter and susceptibility to predation counteract each other, an increased range of predator sizes reduces only slightly the evidence for size-selective mortality, and synchronous spawning and hatching events have the potential to yield strong size-selective mortality of a cohort of fish larvae. The important factors in generating size-selective mortality are either the timing of encounters between fish larvae and their predators or high mortality rates. We demonstrated a direct relationship between the potential of size-selec...
Canadian Journal of Fisheries and Aquatic Sciences, 1997
We examined the sampling variability and capture efficiency of bongo nets and a modified Tucker t... more We examined the sampling variability and capture efficiency of bongo nets and a modified Tucker trawl used in the sampling of ichthyoplankton and other macrozooplankton by taking seven replicate samples at each of two stations on two separate occasions. Sample variance was highly significantly related to sample mean for all major taxonomic categories (i.e., fish eggs, fish larvae, crustaceans, and medusae-chaetognaths). Sampling variability of the bongo nets was significantly greater than that of the Tucker trawl for both fish eggs and larvae. Sampling variability of macrozooplankton was significantly greater than that of ichthyoplankton. For larval fish of 5 mm or less, bongo nets generally yielded higher estimates of abundance than the Tucker trawl and the reverse was true for lengths above 10 mm, but there was a significant influence of species-specific morphological characters. The large sample volume of the Tucker trawl relative to the bongo nets resulted in significantly higher estimates of species diversity for fish eggs and larvae but not for crustaceans or medusae. Although bongo and Tucker samplers are efficient at catching a wide range of sizes of larval fish, the latter's lower variability may make it a more effective sampler. Résumé : Nous avons étudié la variabilité d'échantillonnage et l'efficacité de capture des filets bongo et d'un échantillonneur Tucker modifié utilisés pour échantillonner l'ichtyoplancton et d'autres organismes macrozooplanctoniques en prélevant sept échantillons répétés dans deux stations différentes à deux occasions différentes. La variance de l'échantillon était corrélée de manière hautement significative à la moyenne de l'échantillon pour toutes les grandes catégories taxinomiques (c.-à-d. oeufs de poisson, larves de poisson, crustacés et médusaires-chétognates). La variabilité d'échantillonnage des filets bongo était significativement plus grande que celle de l'échantillonneur Tucker pour les oeufs et les larves de poisson. La variabilité d'échantillonnage du macrozooplancton était substantiellement plus grande que celle de l'ichtyoplancton. Pour les poissons larvaires de 5 mm ou moins, les filets bongo donnaient en général des valeurs estimées de l'abondance plus élevées que l'échantillonneur Tucker et l'inverse se produisait pour les longueurs supérieures à 10 mm, mais il y avait là un effet significatif des caractéristiques morphologiques spécifiques des espèces. Le grand volume d'échantillonnage de l'échantillonneur Tucker par rapport à celui du filet bongo entraîne des valeurs estimées significativement plus élevées de la diversité des espèces dans le cas des oeufs et des larves de poisson, mais non dans celui des crustacés ou des médusaires. Bien que les échantillonneurs bongo et Tucker soient efficaces pour capturer une grande variété de tailles de poissons larvaires, la variabilité plus faible de l'échantillonneur Tucker pourrait en faire un échantillonneur plus efficace. [Traduit par la Rédaction]
Canadian Journal of Fisheries and Aquatic Sciences, 1996
We measured the escape response performance by four species of larval fish: Atlantic cod (Gadus m... more We measured the escape response performance by four species of larval fish: Atlantic cod (Gadus morhua), Atlantic herring (Clupea harengus harengus), radiated shanny (Ulvaria subbifurcata), and capelin (Mallotus villosus). The resultant data were combined with information from larval winter flounder (Pleuronectes americanus) to produce general models relating escape response performance to larval size. Three components of the escape response produced models with reasonable predictive ability, including mean and maximum speed during the response, and the distance travelled by larvae during the first 100 ms of the response (the latter representing the contribution of the C-shaped fast start that initiates the response). The logarithm of mean and maximum escape speed increased linearly with increasing larval length. The distance after 100 ms was linearly related to larval length. Our general model for mean escape speed produced significantly higher length-specific speed values than did the general model proposed by Miller et al. (T.
Biometrics, 1990
We test the robustness of a method for estimating abundance that assumes that the underlying dist... more We test the robustness of a method for estimating abundance that assumes that the underlying distribution of the nonzero observations is lognormal (Pennington, 1983, Biometrics 39, 281-286). Violations in model assumptions that cannot reliably be detected with moderate sample sizes (-40) lead to biases and large reductions in efficiency. Unless it can be clearly demonstrated from repeated sampling that nonzero values follow a lognormal distribution, the sample mean and variance are more robust than lognormal-based estimators of mean and variance of population abundance.
Journal of Experimental Biology
Species with a wide distribution can experience significant regional variation in environmental c... more Species with a wide distribution can experience significant regional variation in environmental conditions, to which they can acclimatize or adapt. Consequently, the geographic origin of an organism can influence its responses to environmental changes, and therefore its sensitivity to combined global change drivers. This study aimed at determining the physiological responses of the northern shrimp, Pandalus borealis, at different levels of biological organization and from four different geographic origins, exposed to elevated temperature and low pH to define its sensitivity to future ocean warming and acidification. Shrimp sampled within the northwest Atlantic were exposed for 30 days to combinations of three temperature (2, 6 or 10°C) and two pH levels (7.75 or 7.40). Survival, metabolic rates, whole-organism aerobic performance and cellular energetic capacity were assessed at the end of the exposure. Our results show that shrimp survival was negatively affected by temperature abov...
Fish and Fisheries
Environmental impacts on fisheries are pervasive, yet methods to account for them in stock assess... more Environmental impacts on fisheries are pervasive, yet methods to account for them in stock assessments and management decisions vary in rigour and quality. The prevalence and efficacy of methods to account for environmental impacts are not well documented, limiting our ability to adequately respond to future environmental and climate changes for adaptive resource management. In Canada, legislation now requires that environmental conditions are considered in the management of fish stocks, yet the current extent of implementation in assessment processes is poorly understood. We assessed the use of climate, oceanographic and ecological considerations in science advisory processes for 178 stock assessments by Fisheries and Oceans Canada. We evaluated whether these considerations were included in conceptual hypotheses about broad‐scale mechanisms, quantitative or qualitative analyses, and the development of management advice on current or future stock status. Conceptual hypotheses were i...
CM Documents - ICES, 2000
We present station-specific depth integrated abundance and biomass of Calanus spp. (stage-specifi... more We present station-specific depth integrated abundance and biomass of Calanus spp. (stage-specific abundance, CI-CVI, of C. finmarchicus, C. glacialis, C. hyperboreus and combined biomass of late stages, CIV-CVI, of Calanus spp.) collected from zooplankton monitoring programs from 19 subregions spanning the Newfoundland and Labrador Shelves, Gulf of St. Lawrence (GSL), Scotian Shelf, and Gulf of Maine (GoM). These data span years 1999-2016, except the southwest GSL subregion (1982-2016) and GoM (1977-2016). We also present data on near surface and bottom temperature and salinity from subregions in Canadian waters. We then present derived annual anomalies of abundance of the three species of Calanus, their combined biomass, and near surface and bottom temperature and salinity from all subregions. This is a contribution by Canadian and USA scientists and their institutions.Sampling and data processing methods are provided in detail in Sorochan et al. (2019), and zooplankton sampling m...
OCEANS 2017 – Anchorage, 2017
Studies investigating the impact of increasing ocean acidification on primary producers have been... more Studies investigating the impact of increasing ocean acidification on primary producers have been largely speculative and based on short-term experimental results. Few long-term studies are available to assess the rate of change in ocean acidity versus change in plankton populations. We utilize long-term observations and historical data based on a network of sites from the northwest Pacific, Arctic, and northwest Atlantic conducted by Fisheries and Oceans Canada to assess temporal change in ocean pH levels. We utilize both recent and long-term plankton data based on an ocean monitoring program initiated in the late 1990's and derived from the Continuous Plankton Recorder (CPR) Survey in the northwest Atlantic to assess interannual and decadal changes in acid-sensitive taxa back to the 1960's. We discuss these findings in light of the major uncertainties surrounding ocean acidification and how they will impact plankton in the marine ecosystem.
Biological oceanography, 2013
AbstractA simulation study of the influence of variations in food and predator abundance on growt... more AbstractA simulation study of the influence of variations in food and predator abundance on growth and survival of larval fish was conducted to determine whether changes in the abundance of either variable could be detected from analysis of size frequency data or from growth histories. The results indicate that estimates of the mean and variance in size frequency distribution would have to be very precise to detect changes in predator abundance. The mean and variance in individual growth rates appear to be useful tools to determine whether changes in predator or food abundance are influencing larval fish survival. As food abundance increases, the mean and variance in growth rates increase. However, as predator abundance increases, the variance in growth rates, for any given mean, decreases.
The MAPPS global database of photosynthesis-irradiance (P-E) parameters consists of over 5000 P-E... more The MAPPS global database of photosynthesis-irradiance (P-E) parameters consists of over 5000 P-E experiments that provides information on the spatio-temporal variability in the two P-E parameters (the assimilation number, and the initial slope) that are fundamental inputs for models of marine primary production that use chlorophyll as the state variable. The experiments were carried out by an international group of research scientists to examine the basin-scale variability in the photophysiological response of marine phytoplankton over a range of oceanic regimes (from the oligotrophic gyres to productive shelf systems) and covers several decades. These data can be used to improve the assignment of P-E parameters in the estimation of marine primary production using satellite data.
&... more <p>Located on a crossroads of some of the main currents associated to the Atlantic meridional overturning circulation (AMOC), Newfoundland and Labrador (NL) shelves are specially affected by changes in large-scale ocean circulation. Such circulation changes impact not only the regional climate, but also the overall water masses composition, with consequences on physical conditions, nutrient availability, oxygen content, pH, etc. Systematic hydrographic observations of this system have been carried out by Canada and other countries since 1948. The observational program was reinforced in 1999 with the creation of the Atlantic Zone Monitoring Program (AZMP), ensuring enhanced seasonal coverage and new biogeochemical observations. In 2014, this monitoring was augmented with the monitoring of ocean acidification parameters. Here we review historical physical-biogeochemical changes on the NL shelves, with an emphasis on low frequency variability and cycles. Results suggest, for example, that the cold intermediate layer (CIL), a cold mid-depth layer that is a key feature of the NL ecosystem, exhibited profound changes during the last 70 years. In the mid 60's, the CIL was anomalously warm compared to the rest of the time series. This warm period was followed by a cold period centered in the early 90's. Historical salinity records also suggest that fresher waters are found during warmer years, and vice-versa. Nitrate/Phosphate ratios suggest recent changes in water masses composition towards less Arctic waters flowing on the shelves. This is concurrent with a reduction in nutrients concentration on the NL shelves since about 2012, together with changes in the strength of the Labrador Current along the shelf.</p>
Other in Ices Annual Sciences Conference 23 09 Aberdeen Uk, 2005
Biological Oceanography, 1988
Journal of Fish Biology, 1989
Most studies on feeding‐related activities of fish in cold water (0° C) have not used eurythermal... more Most studies on feeding‐related activities of fish in cold water (0° C) have not used eurythermal species or examined a broad suite of activities. In this study we report on the feeding, growth, behaviour and conversion‐efficiency of 0 + Atlantic cod in response to water temperature and food availability. In one experiment, activity, opercular beat and growth decreased with decreasing temperature over the range 8·3–0·6° C. However, the conversion efficiency increased with decreasing temperature, a result partly explained by the relative change in activity and opercular rate. In another experiment, temperature had a linear effect on growth in cod fed different food rations. Both food availability and temperature were found to influence growth in group 0 + cod. The specific growth rate of cod in this experiment exceeded 2% day‐1. Growth data collected from cod sampled in the field during the cold‐water period showed a progressive increase of mean length over the season. Overall, these...
The Atlantic Zone …
... in Flemish Cap and Slope Waters Compared With the Adjacent Grand Banks Gary Maillet, Pierre P... more ... in Flemish Cap and Slope Waters Compared With the Adjacent Grand Banks Gary Maillet, Pierre Pepin, Joe Craig, Sandra Fraser and Dan ... mer compared to those observed on the GB Shelf (Table 1). The large difference in inventories during this seasonal transi-tion would ...
Canadian Journal of Fisheries and Aquatic Sciences, 1999
We investigated the effects of size-dependent encounter and susceptibility, the role of variation... more We investigated the effects of size-dependent encounter and susceptibility, the role of variation in the size distribution of predators, and the timing of prey-predator interaction during the larval phase in shaping the length frequency distribution of surviving fish larvae. These analyses based on general empirical size-dependent relationships may have broad implications in understanding larval fish cohort dynamics. We demonstrated that the formulations of encounter and susceptibility to predation counteract each other, an increased range of predator sizes reduces only slightly the evidence for size-selective mortality, and synchronous spawning and hatching events have the potential to yield strong size-selective mortality of a cohort of fish larvae. The important factors in generating size-selective mortality are either the timing of encounters between fish larvae and their predators or high mortality rates. We demonstrated a direct relationship between the potential of size-selec...
Canadian Journal of Fisheries and Aquatic Sciences, 1997
We examined the sampling variability and capture efficiency of bongo nets and a modified Tucker t... more We examined the sampling variability and capture efficiency of bongo nets and a modified Tucker trawl used in the sampling of ichthyoplankton and other macrozooplankton by taking seven replicate samples at each of two stations on two separate occasions. Sample variance was highly significantly related to sample mean for all major taxonomic categories (i.e., fish eggs, fish larvae, crustaceans, and medusae-chaetognaths). Sampling variability of the bongo nets was significantly greater than that of the Tucker trawl for both fish eggs and larvae. Sampling variability of macrozooplankton was significantly greater than that of ichthyoplankton. For larval fish of 5 mm or less, bongo nets generally yielded higher estimates of abundance than the Tucker trawl and the reverse was true for lengths above 10 mm, but there was a significant influence of species-specific morphological characters. The large sample volume of the Tucker trawl relative to the bongo nets resulted in significantly higher estimates of species diversity for fish eggs and larvae but not for crustaceans or medusae. Although bongo and Tucker samplers are efficient at catching a wide range of sizes of larval fish, the latter's lower variability may make it a more effective sampler. Résumé : Nous avons étudié la variabilité d'échantillonnage et l'efficacité de capture des filets bongo et d'un échantillonneur Tucker modifié utilisés pour échantillonner l'ichtyoplancton et d'autres organismes macrozooplanctoniques en prélevant sept échantillons répétés dans deux stations différentes à deux occasions différentes. La variance de l'échantillon était corrélée de manière hautement significative à la moyenne de l'échantillon pour toutes les grandes catégories taxinomiques (c.-à-d. oeufs de poisson, larves de poisson, crustacés et médusaires-chétognates). La variabilité d'échantillonnage des filets bongo était significativement plus grande que celle de l'échantillonneur Tucker pour les oeufs et les larves de poisson. La variabilité d'échantillonnage du macrozooplancton était substantiellement plus grande que celle de l'ichtyoplancton. Pour les poissons larvaires de 5 mm ou moins, les filets bongo donnaient en général des valeurs estimées de l'abondance plus élevées que l'échantillonneur Tucker et l'inverse se produisait pour les longueurs supérieures à 10 mm, mais il y avait là un effet significatif des caractéristiques morphologiques spécifiques des espèces. Le grand volume d'échantillonnage de l'échantillonneur Tucker par rapport à celui du filet bongo entraîne des valeurs estimées significativement plus élevées de la diversité des espèces dans le cas des oeufs et des larves de poisson, mais non dans celui des crustacés ou des médusaires. Bien que les échantillonneurs bongo et Tucker soient efficaces pour capturer une grande variété de tailles de poissons larvaires, la variabilité plus faible de l'échantillonneur Tucker pourrait en faire un échantillonneur plus efficace. [Traduit par la Rédaction]
Canadian Journal of Fisheries and Aquatic Sciences, 1996
We measured the escape response performance by four species of larval fish: Atlantic cod (Gadus m... more We measured the escape response performance by four species of larval fish: Atlantic cod (Gadus morhua), Atlantic herring (Clupea harengus harengus), radiated shanny (Ulvaria subbifurcata), and capelin (Mallotus villosus). The resultant data were combined with information from larval winter flounder (Pleuronectes americanus) to produce general models relating escape response performance to larval size. Three components of the escape response produced models with reasonable predictive ability, including mean and maximum speed during the response, and the distance travelled by larvae during the first 100 ms of the response (the latter representing the contribution of the C-shaped fast start that initiates the response). The logarithm of mean and maximum escape speed increased linearly with increasing larval length. The distance after 100 ms was linearly related to larval length. Our general model for mean escape speed produced significantly higher length-specific speed values than did the general model proposed by Miller et al. (T.
Biometrics, 1990
We test the robustness of a method for estimating abundance that assumes that the underlying dist... more We test the robustness of a method for estimating abundance that assumes that the underlying distribution of the nonzero observations is lognormal (Pennington, 1983, Biometrics 39, 281-286). Violations in model assumptions that cannot reliably be detected with moderate sample sizes (-40) lead to biases and large reductions in efficiency. Unless it can be clearly demonstrated from repeated sampling that nonzero values follow a lognormal distribution, the sample mean and variance are more robust than lognormal-based estimators of mean and variance of population abundance.