Sarah E. Dudas

INVASION DYNAMICS OF THE VARNISH CLAM (NUTTALLIA OBSCURATA): A MATRIX DEMOGRAPHIC MODELING APPROACH

Marine invaders have become a significant threat to native biodiversity and ecosystem function. In this study, the invasion of the varnish clam (Nuttallia obscurata) in British Columbia, Canada, is investigated using a matrix modeling approach to identify the life history characteristics most crucial for population growth and to investigate population differences. Mark-recapture analyses and field collections from 2003 to 2004 were used to determine individual growth, survival rates, and fecundity for two sites. A multi-state matrix model was used to determine population growth rates and to conduct sensitivity and elasticity analyses. A life table response experiment was also used to determine what life history stage contributed most to observed differences in population growth rates. Population survey data were used in conjunction with the matrix model to determine plausible recruitment levels and to investigate recruitment scenarios. Both populations are currently declining but are likely sustainable because of the pulsed nature of large recruitment events. Survival of larger clams (>40 mm) is the most important for population growth based on elasticity and sensitivity analyses. Adult survival also had the largest influence on observed differences between site-specific population growth rates. The two populations studied differed in recruitment dynamics; one experiencing annual recruitment with higher post-settlement mortality and the other, episodic recruitment and lower post-settlement mortality. The most influential factor for the successful invasion of the varnish clam appears to be survival of the larger size classes. Therefore, any process that decreases adult survival (e.g., predation, commercial harvest) will have the greatest impact on population growth.

Assessing the effect of aquatic noise on fish behavior and physiology: a meta-analysis approach

Due to the extreme distance that sounds can travel through water, many marine species rely on the soundscape for auditory information regarding predator or prey locations, communication, and habitat selection. These species not only take advantage of the prevailing sounds but also contribute to the soundscape through their own vocalizations. Certain sounds have been shown to have negative effects on marine species, resulting in disrupted communication and unbalanced predator-prey interactions. Unfortunately, the vast majority of soundscape studies are biased towards marine mammals, and only recently has attention been directed towards the potential repercussions for fishes. In an attempt to determine the implications that changes to the soundscape may have on the fishes, a meta-analysis was conducted focusing primarily on the role that anthropogenic noises may play in altering fish behavior and physiology. The review identified 3,174 potentially relevant papers of which were 27 used. The analysis indicate...

The effect of anthropogenic and biological noise on fish behavior and physiology: A meta-analysis

Aquatic noise has the potential to travel extreme distances and as such many marine species rely on the soundscape for auditory information regarding habitat selection, predator or prey locations, and communication. These species not only take advantage of the prevailing sounds but also contribute to the soundscape through their own vocalizations. Certain sounds have the potential to negatively effect marine species resulting in unbalanced predator-prey interactions and disrupted communication. In an attempt to determine the implications that changes to the soundscape may have on fishes, we conducted a meta-analysis focusing on how anthropogenic and biological noises may alter fish behavior and physiology. We reviewed 3,174 potentially relevant papers of which 44 met our criteria and were used in the analysis. Results indicated that anthropogenic noise has an adverse effect on marine and freshwater fish behavior and physiology. Alternatively biological and environmental noises did not significantly alter fish behavior and physiology. These findings suggest that although certain species may be more susceptible to anthropogenic noise than others, the vast majority of fish have the potential to be negatively affected by noise pollution, while biological noises may not have the same negative consequences for fish behavior and physiology.Aquatic noise has the potential to travel extreme distances and as such many marine species rely on the soundscape for auditory information regarding habitat selection, predator or prey locations, and communication. These species not only take advantage of the prevailing sounds but also contribute to the soundscape through their own vocalizations. Certain sounds have the potential to negatively effect marine species resulting in unbalanced predator-prey interactions and disrupted communication. In an attempt to determine the implications that changes to the soundscape may have on fishes, we conducted a meta-analysis focusing on how anthropogenic and biological noises may alter fish behavior and physiology. We reviewed 3,174 potentially relevant papers of which 44 met our criteria and were used in the analysis. Results indicated that anthropogenic noise has an adverse effect on marine and freshwater fish behavior and physiology. Alternatively biological and environmental noises did not significantly alter ...

Microplastics in juvenile Chinook salmon and their nearshore environments on the east coast of Vancouver Island

Microplastics are a significant issue in the worlds oceans. These small plastic particles (<5 mm in size) are becoming globally ubiquitous in the marine environment and are ingested by various fish species. Here we investigate the incidence of microplastics in juvenile Chinook salmon and their nearshore marine environments on the east coast of Vancouver Island, British Columbia. We completed a series of beach seines, plankton tows and sediment cores in nearshore areas of importance to juvenile salmon. Microplastics were extracted from fish, water and sediment samples and concentrations were quantified. Microplastics analysis, consisting predominantly of fibrous plastics, showed juvenile Chinook salmon contained 1.2 ± 1.4 (SD) microplastics per individual while water and sediment samples had 659.9 ± 520.9 microplastics m-3 and 60.2 ± 63.4 microplastics kg-1 dry weight, respectively. We found no differences in microplastic concentrations in juvenile Chinook and water samples among sites but observed significantly higher concentrations in sediment at the Deep Bay site compared to Nanaimo and Cowichan Bay sites. Chinook microplastic concentrations were relatively low compared to literature values and, given the size and type of microplastics we observed, are unlikely to represent an immediate threat to fish in this area. However, microplastics less than 100 μm in size were not included in the study and may represent a greater threat due to their ability to translocate through tissues.

Sound the alarm: A meta-analysis on the effect of aquatic noise on fish behavior and physiology

The aquatic environment is increasingly bombarded by a wide variety of noise pollutants whose range and intensity are increasing with each passing decade. Yet, little is known about how aquatic noise affects marine communities. To determine the implications that changes to the soundscape may have on fishes, a meta-analysis was conducted focusing on the ramifications of noise on fish behavior and physiology. Our meta-analysis identified 42 studies that produced 2,354 data points, which in turn indicated that anthropogenic noise negatively affects fish behavior and physiology. The most predominate responses occurred within foraging ability, predation risk, and reproductive success. Additionally, anthropogenic noise was shown to increase the hearing thresholds and cortisol levels of numerous species while tones, biological, and environmental noise were most likely to affect complex movements and swimming abilities. These findings suggest that the majority of fish species are sensitive to changes in the aquatic soundscape, and depending on the noise source, species responses may have extreme and negative fitness consequences. As such, this global synthesis should serve as a warning of the potentially dire consequences facing marine ecosystems if alterations to aquatic soundscapes continue on their current trajectory.

Community assessment techniques and the implications for rarefaction and extrapolation with Hill numbers

Abstract Diversity estimates play a key role in ecological assessments. Species richness and abundance are commonly used to generate complex diversity indices that are dependent on the quality of these estimates. As such, there is a long‐standing interest in the development of monitoring techniques, their ability to adequately assess species diversity, and the implications for generated indices. To determine the ability of substratum community assessment methods to capture species diversity, we evaluated four methods: photo quadrat, point intercept, random subsampling, and full quadrat assessments. Species density, abundance, richness, Shannon diversity, and Simpson diversity were then calculated for each method. We then conducted a method validation at a subset of locations to serve as an indication for how well each method captured the totality of the diversity present. Density, richness, Shannon diversity, and Simpson diversity estimates varied between methods, despite assessments occurring at the same locations, with photo quadrats detecting the lowest estimates and full quadrat assessments the highest. Abundance estimates were consistent among methods. Sample‐based rarefaction and extrapolation curves indicated that differences between Hill numbers (richness, Shannon diversity, and Simpson diversity) were significant in the majority of cases, and coverage‐based rarefaction and extrapolation curves confirmed that these dissimilarities were due to differences between the methods, not the sample completeness. Method validation highlighted the inability of the tested methods to capture the totality of the diversity present, while further supporting the notion of extrapolating abundances. Our results highlight the need for consistency across research methods, the advantages of utilizing multiple diversity indices, and potential concerns and considerations when comparing data from multiple sources.

Is commercial harvesting of beach‐cast seaweed ecologically sustainable?

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