Jason F. Schreer

Comparative diving patterns of pinnipeds and seabirds

General ecological information resulting from modern dive studies has been limited because analyses and conclusions are study- and species-specific. In this work, a series of unrelated divers was studied and compared using the same analytical procedures. More than 230 000 dives from 12 species were analyzed, and ∼140 000 of these dives were classified according to dive shape. The species included one cormorant, three penguins, two eared seals, five true seals, and a walrus. Dive profiles could generally be characterized as one of four shapes: square, V, skewed right, or skewed left. In light of this, a universal shape classification protocol was developed that also offers potential solutions for “on board” memory limitations and transmission constraints for archival time–depth recorders and satellite-linked time–depth recorders. Comparisons of dive data recorded with different sample intervals indicated the need for a standardization relative to mean dive duration (i.e., an equal number of data points per...

The Influence of Terminal Tackle on Injury, Handling Time, and Cardiac Disturbance of Rock Bass

Abstract We studied the effects of catch-and-release angling on rock bass Ambloplites rupestris a small but common centrarchid species in North America. A field study of hooking injury and mortality was conducted in Lake Erie at a water temperature of 16°C. We captured fish using one of four terminal tackle types: barbless worm, barbed worm, barbless jig, and barbed jig. No mortality was observed in any of the four treatments even after holding fish for 5 d. Fish captured using worms were hooked more deeply than fish caught on jigs. Fish captured on barbless jigs were unhooked most easily and more rapidly than with all other tackle types, resulting in an average of only 20 s of air exposure. Because they were more difficult to remove from the hook, fish captured on other terminal tackle experienced at least twice as much air exposure. To assess sublethal effects, we measured the cardiac responses of rock bass exposed to 30 s of simulated angling followed by 30 or 180 s of air exposure. These air exposure ...

Cardiac Response to Variable Forced Exercise at Different Temperatures: An Angling Simulation for Smallmouth Bass

Abstract Longer angling durations (capture by hook and line) and higher water temperatures are generally thought to be more detrimental to angled fish. Here, this concept was investigated in smallmouth bass Micropterus dolomieu by monitoring cardiac output (CO) and its components, heart rate (HR) and stroke volume (SV), before, during, and after a simulated angling event in a Blazka-type respirometer. Fish (total n = 31) were acclimated to 12, 16, or 20°C and exposed to conditions that elicited repeated burst swimming either briefly (20 s) or to exhaustion (120–180 s). Resting CO and HR increased significantly with increasing temperature (Q 10 ∼ 2), indicating temperature conformity, whereas SV was not affected by temperature. Recovery times (time after angling until cardiac parameters returned to resting levels) ranged from 0 to 85 min (mean ∼ 40 min) for briefly angled fish and from 20 to 210 min (mean ∼ 105 min) for exhaustively angled fish. These recovery times increased significantly with angling dur...

The Effect of Scented Lures on the Hooking Injury and Mortality of Smallmouth Bass Caught by Novice and Experienced Anglers

Abstract Although regulations prohibiting the use of natural baits are relatively common, new regulations specifically targeting the use of chemical attractants have recently been implemented. While no citeable evidence for these new regulations exists, they may have been promulgated due to a perceived increase in the risk of fish mortality from scented lures compared with unscented lures. The present study investigated the hooking injury and short-term mortality of 238 adult smallmouth bass Micropterus dolomieu captured on Lake Erie by both experienced (fished > 100 d/year) and novice (fished < 10 d/year) anglers on actively fished jigs similarly threaded with minnows, nonscented plastic grubs, or grubs scented with chemical attractants. The depth of hook ingestion, the anatomical hooking location, the presence of bleeding at the hook wound, and the total amount of time taken to remove the hook were noted on all captured fish. The fish were then transferred to a retention cage, and their survival was mon...

Classification of Dive Profiles: A Comparison of Statistical Clustering Techniques and Unsupervised Artificial Neural Networks

Recent advances in technology for sampling diving behavior have enabled enormous datasets to be collected on a variety of diving animals. Methods used to analyze these data vary considerably across studies, complicating interspecific comparisons. The primary problem is that methods for analyzing large datasets of dive profiles have not been clearly defined. This study examines various algorithms for analyzing multivariate observations and assesses their suitability for classifying diving data. These include k-means and fuzzy c-means clustering techniques from the field of statistics, and Kohonen self-organizing map (SOM) and fuzzy adaptive resonance theory (ART) from the field of artificial neural networks. A Monte Carlo simulation was performed on artificially generated data, with known solutions, to test clustering performance under various conditions (i.e., well defined or overlapping groups, varying numbers of variables, varying numbers of groups, and autocorrelated or independent variables). Performance was also tested on real datasets from Adelie penguins (Pygoscelis adeliae), southern elephant seals (Mirounga leonina), and Weddell seals (Leptonychotes weddellii). K-means, fuzzy c-means, and SOM all performed equally well on the artificially generated data while fuzzy ART had misclassification rates that were twice as high. All techniques showed decreasing performance with increasing overlap among groups and increasing numbers

Cardiovascular Responses of Largemouth Bass to Exhaustive Exercise and Brief Air Exposure over a Range of Water Temperatures

Abstract In this study we examined the effects of exhaustive exercise and brief air exposure on the cardiovascular function of largemouth bass Micropterus salmoides at four water temperatures (13, 17, 21, and 25°C). We used Doppler flow probes to monitor cardiac output and its components (i.e., stroke volume and heart rate) while we manually chased fish to exhaustion to simulate angling, exposed them to air for 30 s, and then recorded patterns of recovery. Resting cardiac variables generally increased with increasing water temperature except for stroke volume, which was temperature independent. Fish heart rate became erratic during exercise, and during air exposure fish exhibited severe bradycardia before becoming tachycardic when returned to the water. Maximal change occurred most rapidly for cardiac output (about 5 min). Several minutes later, changes in heart rate (increase) and stroke volume (decrease) simultaneously reached maximal deviations from resting values. Cardiac output and heart rate increas...

Swimming Performance of Brook Trout after Simulated Catch-and-Release Angling: Looking for Air Exposure Thresholds

Abstract Air exposure has been hypothesized as one of the primary stressors present during catch-and-release angling. However, there are few studies that systematically vary air exposure duration and evaluate the consequences on individual fish. Here, we evaluated the short-term, sublethal effects of exercise (to simulate angling) and air exposure on the swimming performance of hatchery brook trout Salvelinus fontinalis at 10°C. The duration of the angling event (i.e., chasing the fish by hand) was held constant at 30 s, while air exposure duration was systematically varied between 0, 30, 60, and 120 s. The results showed that air exposures of 60 s or less did not affect swimming performance. However, air exposure of 120 s resulted in a dramatic (∼75%) reduction in swimming performance. In fact, nearly half of the fish held out of the water for 120 s were unwilling or unable to swim at all. No mortality was observed after any of the treatments (fish were monitored for 3 months). This work suggests that fi...

Low temperature cardiac response to exhaustive exercise in fish with different levels of winter quiescence

We examined the cardiac responses of different fish species to anaerobic exercise at low temperatures (3 degrees C). Three species of sympatric warmwater fish with perceived differences in winter activity were used for this comparative study: the winter-quiescent largemouth bass (Micropterus salmoides); the winter-active white bass (Morone chrysops); and the intermediately winter-active black crappie (Pomoxis nigromaculatus). Perceived differences in winter activity were reflected in cardiac responses; e.g. basal cardiac values were lowest for largemouth bass, highest for white bass, and intermediate for black crappie. In addition, cardiac recovery was most rapid for white bass, slowest for largemouth bass and intermediate for black crappie. When disturbed at low temperatures, largemouth bass and black crappie elevated cardiac output principally through increases in heart rate despite substantial decreases in stroke volume. Conversely, white bass principally used stroke volume modulation to change cardiac output. The results of this study indicate that different species respond differently to exercise at low temperatures. Management strategies should recognize that such variation exists and ensure that management decisions are based upon an understanding of the low temperature exercise physiology and winter biology of the species of interest.

Diving Heart Rate Development in Postnatal Harbour Seals, Phoca vitulina

Harbour seals, Phoca vitulina, dive from birth, providing a means of mapping the development of the diving response, and so our objective was to investigate the postpartum development of diving bradycardia. The study was conducted May–July 2000 and 2001 in the St. Lawrence River Estuary (48°41′N, 68°01′W). Both depth and heart rate (HR) were remotely recorded during 86,931 dives (ages 2–42 d, n = 15) and only depth for an additional 20,300 dives (combined data covered newborn to 60 d, n = 20). The mean dive depth and mean dive durations were conservative during nursing (2.1 ± 0.1 m and 0.57 ± 0.01 min, range = 0–30.9 m and 0–5.9 min, respectively). The HR of neonatal pups during submersion was bimodal, but as days passed, the milder of the two diving HRs disappeared from their diving HR record. By 15 d of age, most of the dive time was spent at the lower diving bradycardia rate. Additionally, this study shows that pups are born with the ability to maintain the lower, more fully developed dive bradycardia during focused diving but do not do so during shorter routine dives.

Environmental monitoring using physiological telemetry: A case study examining common carp responses to thermal pollution in a coal-fired generating station effluent

During the winters of 1998 and 1999, the response of common carp (Cyprinus carpio) to fluctuating thermal conditions was studied in the Nanticoke Thermal Generating Station discharge canal on Lake Erie. Locomotory activity of fish in the canal was monitored using electromyogram telemetry of the axial musculature. Carp activity was variable but, in general, they were more active during times of rising and falling temperatures, and were least active during stable periods. The magnitude of water temperature fluctuation was not correlated with activity. Locomotory activity of fish was not generally correlated with absolute water temperature over a wide range of temperatures (∼2 to 18 °C) when examined on an hourly basis, but was moderately correlated at a finer temporal resolution (5 min). During a station shutdown, one carp stayed in the canal and experienced a substantial decrease in temperature yet exhibited no significant change in activity. The results of this study suggest that minor temperature changes (∼0.1 °C per hour) are sufficient to alter activity, probably through fine scale behavioral thermoregulation. The heightened activity resulting from slight changes in temperature may be energetically costly in environments that change as rapidly as thermal effluents. Physiological telemetry permitted us to study the in situ response of fish to dynamic environmental conditions with more precision than is possible using locational telemetry. We suggest that physiological telemetry can provide insights into the behavioral and physiological responses of fish to a diversity of pollutants and represents a robust environmental monitoring technique.