Ecology of common bully (Gobiomorphus cotidianus) in the Tarawera and Rangitaiki rivers: isolation by inland distance or anthropogenic discharge?

Previous research has identified distinct genetic, life-history and reproductive differences between populations of common bully (Gobiomorphus cotidianus) upstream and downstream of a pulp and paper mill outfall on the Tarawera River in the Bay of Plenty, New Zealand. This study investigated the distribution of common bully in the Tarawera River by examining fish collected from upstream (37 km inland) and downstream (20 km inland) locations and comparing them to fish from similar inland locations (40 km and 17 km inland, respectively) in the nearby Rangitaiki River. Reproductive divergence was observed between upstream and downstream sites of both rivers by differing annual trends in gonadosomatic index. Stable carbon and nitrogen isotopes confirmed residency at each sampling site and otolith microchemistry demonstrated different life-history strategies between upstream and downstream populations. Diadromous recruits dominated in both downstream river populations, with a general disappearance of diadromy upstream. A mixture of diadromous and non-diadromous fish were found in the upstream Rangitaiki River, whereas diadromous recruits were absent in the upstream Tarawera River. A reduction in oculoscapular canal structures also coincided with loss of diadromy in fish from both rivers. A behavioural study to determine whether pulp and paper mill effluent may deter fish migration within the Tarawera River demonstrated a strong avoidance of effluent, but only at concentrations (>25%) greater than those that naturally occur in the river (<15%). The results of this study suggest that combinations of influences coupled with inland distance are likely to be responsible for the isolation of common bully subpopulations within the Tarawera River

PERFORMANCE OF FISH LARVAE: EFFECTS OF ATRAZINE,

To my husband, Rafael Perez, to whom I owe everything, who has been with me through the “good and the bad”. To my son, Diego T. Perez, and my daughter, Cecilia A. Perez, who have always brightened my day with laughter and love. And to my parents, Alvaro Alvarez and Marie Cecilie d’Otreppe de Bouvette, who, without ever a doubt, have supported me on every decision I have made. Thank you. Acknowledgements I wish to thank my adviser Dr. Lee A. Fuiman, for his guidance, support, and encouragement. I am also grateful to the members of my committee, Dr. David P. Crews, Dr. G. Joan Holt, Dr. B. Scott Nunez and Dr. Peter Thomas for their helpful suggestions and critical review of this dissertation. Thanks to my laboratory mates; Hunter Samberson and Brie Sarkisian for their help with fish rearing; Ian McCarthy for helping with fish rearing and collection of data, and Kiersten Madden for her support and critique of this work. My special thanks to Rafael Perez, Scott Applebaum, and Ian McCarthy for discussion in the development of the research presented here. I am sincerely thankful to all my friends at the Marine Science Institute and Port Aransas for their help and support, without whom this dissertation would not have happened. v SIGNIFICANCE OF ENVIRONMENTALLY REALISTI

Escape path complexity and its context dependency in Pacific blue-eyes (Pseudomugil signifer)

The escape paths prey animals take following a predatory attack appear to be highly unpredictable - a property that has been described as ‘protean behaviour’. Here we present a method of quantifying the escape paths of individual animals using a path complexity approach. When individual fish (Pseudomugil signifer) were attacked, we found that a fish's movement path rapidly increased in complexity following the attack. This path complexity remained elevated (indicating a more unpredictable path) for a sustained period (at least 10 seconds) after the attack. The complexity of the path was context dependent; paths were more complex when attacks were made closer to the fish, suggesting that these responses are tailored to the perceived level of threat. We separated out the components of speed and turning rate changes to determine which of these components contributed to the overall increase in path complexity following an attack. We found that both speed and turning rate measures contributed similarly to an individual's path complexity in absolute terms. Overall, our work highlights the context dependent escape responses that animals use to avoid predators and also provides a method for quantifying the escape paths of animals

Burst‐Swimming Performance of Larval Zebra Danios and the Effects of Diel Temperature Fluctuations

Zebra danios Danio [Brachydanio] rerio were spawned and their eggs and larvae were reared in a simulated natural thermal regime, increasing from 21 to 30°C for 7 h and decreasing to 21°C for 17 h, daily. Burst‐swimming performance was provoked by electrical stimulation of larvae (mean total length = 3.6 mm). Responses were filmed at 400 frames/s at temperature intervals of 3°C. Distance travelled in a specified time (St), maximum velocity, and maximum acceleration increased with temperature. Size‐specific maximum velocity was considerably higher than previously reported for larvae. A predictive model relating St to temperature was developed. In theory, the observed effects of temperature could have been due to changes in physiological rates or in water viscosity, but Reynolds numbers were too high for a substantial viscosity effect. The Q10 for St was 1.6, that for maximum velocity was 1.4. Results suggest that, other factors being equal, larvae are potentially more vulnerable to predation at sunrise or at other times when water temperature is low.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141859/1/tafs0143.pd

Ontogenetic change in predicted acoustic pressure sensitivity in larval red drum (Sciaenops ocellatus)

Author Posting. © Company of Biologists, 2019. This article is posted here by permission of Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology 222(16), (2019): jeb.201962, doi:10.1242/jeb.201962.Detecting acoustic pressure can improve a fish's survival and fitness through increased sensitivity to environmental sounds. Pressure detection results from interactions between the swim bladder and otoliths. In larval fishes, those interactions change rapidly as growth and development alter bladder dimensions and otolith–bladder distance. We used computed tomography imagery of lab-reared larval red drum (Sciaenops ocellatus) in a finite-element model to assess ontogenetic changes in acoustic pressure sensitivity in response to a plane wave at frequencies within the frequency range of hearing by fishes. We compared the acceleration at points on the sagitta, asteriscus and lapillus when the bladder was air filled with results from models using a water-filled bladder. For larvae of 8.5–18 mm in standard length, the air-filled bladder amplified simulated otolith motion by a factor of 54–3485 times that of a water-filled bladder at 100 Hz. Otolith–bladder distance increased with standard length, which decreased modeled amplification. The concomitant rapid increase in bladder volume partially compensated for the effect of increasing otolith–bladder distance. Calculated resonant frequency of the bladders was between 8750 and 4250 Hz, and resonant frequency decreased with increasing bladder volume. There was a relatively flat frequency dependence of these effects in the audible frequency range, but we found a small increase in amplification with increasing excitation frequency. Using idealized geometry, we found that the larval vertebrae and ribs have negligible influence on bladder motion. Our results help clarify the auditory consequences of ontogenetic changes in bladder morphology and otolith–bladder relationships during larval stages.This work was supported by the American Museum of Natural History Lerner Gray Fund for Marine Research (to A.K.S.), the Perry R. Bass Endowment at the University of Texas Marine Science Institute (to L.A.F.), and the Office of Naval Research Ocean Acoustics Program (grant number N00014-15-1-2032 to P.S.W.).2020-08-0

Animal escapology I: theoretical issues and emerging trends in escape trajectories

Escape responses are used by many animal species as their main defence against predator attacks. Escape success is determined by a number of variables; important are the directionality (the percentage of responses directed away from the threat) and the escape trajectories (ETs) measured relative to the threat. Although logic would suggest that animals should always turn away from a predator, work on various species shows that these away responses occur only approximately 50–90% of the time. A small proportion of towards responses may introduce some unpredictability and may be an adaptive feature of the escape system. Similar issues apply to ETs. Theoretically, an optimal ET can be modelled on the geometry of predator–prey encounters. However, unpredictability (and hence high variability) in trajectories may be necessary for preventing predators from learning a simple escape pattern. This review discusses the emerging trends in escape trajectories, as well as the modulating key factors, such as the surroundings and body design. The main ET patterns identified are: (1) high ET variability within a limited angular sector (mainly 90–180deg away from the threat; this variability is in some cases based on multiple peaks of ETs), (2) ETs that allow sensory tracking of the threat and (3) ETs towards a shelter. These characteristic features are observed across various taxa and, therefore, their expression may be mainly related to taxon-independent animal design features and to the environmental context in which prey live – for example whether the immediate surroundings of the prey provide potential refuges

FishSizer: Software solution for efficiently measuring larval fish size

Length and depth of fish larvae are part of the fundamental measurements in many marine ecology studies involving early fish life history. Until now, obtaining these measurements has required intensive manual labor and the risk of inter- and intra-observer variability. We developed an open-source software solution to semi-automate the measurement process and thereby reduce both time consumption and technical variability. Using contrast-based edge detection, the software segments images of a fish larva into “larva” and “background.” Length and depth are extracted from the “larva” segmentation while taking curvature of the larva into consideration. The graphical user interface optimizes workflow and ease of usage, thereby reducing time consumption for both training and analysis. The software allows for visual verification of all measurements. A comparison of measurement methods on a set of larva images showed that this software reduces measurement time by 66%–78% relative to commonly used software. Using this software instead of the commonly used manual approach has the potential to save researchers from many hours of monotonous work. No adjustment was necessary for 89% of the images regarding length (70% for depth). Hence, the only workload on most images was the visual inspection. As the visual inspection and manual dimension extraction works in the same way as currently used software, we expect no loss in accuracy.publishedVersio

Ontogeny of visual and mechanosensory structure and function in atlantic menhaden Brevoortia tyrannus

The importance of visual, mechanoreceptive and auditory inputs to escape responses was examined in larvae of the Atlantic menhaden (Brevoortia tyrannus) presented with a simulated predatory stimulus. Ontogenetic changes in the retina, superficial neuromasts and auditory bullae were examined in concert with behavioral trials in which sensory inputs were selectively blocked. Menhaden larvae showed a decrease in cone photoreceptor density and first developed rod photoreceptors when their total length (TL) reached 8-10 mm; they began summing photoreceptive inputs at 12-14 mm TL. Inflation of the auditory bullae was complete by 15 mm TL. The proliferation of superficial neuromasts varied depending on their location, with cephalic superficial neuromasts decreasing in number beginning at 19 mm TL and numbers of trunk neuromasts continuing to increase throughout the larval period. In behavioral trials, responsiveness and the reactive distance to the approaching probe increased with increasing larva total length when all sensory inputs were available (control larvae). When visual inputs were blocked, responsiveness was lower than in control larvae, but still increased ontogenetically, while reactive distance showed no difference between control larvae and those lacking visual information. When neuromasts were ablated, ontogenetic increases in responsiveness and reactive distance were absent. Inflation of the auditory bullae had no discernible effect on behavior. The anatomical and behavioral results suggest that both vision and mechanoreception are used to trigger a response to a looming predatory stimulus and that mechanoreception, but not vision, contributes to the timing of the response. Ontogenetic improvements in performance are attributed mainly to neuromast proliferation and not to ontogenetic changes in the retina