Maximum diving depths and durations were examined in relation to body mass for birds, marine mammals, and marine turtles. There were strong allometric relationships between these parameters (log10 transformed) among air-breathing vertebrates (r = 0.71, n = 111 for depth; r = 0.84, n = 121 for duration), although there was considerable scatter around the regression lines. Many of the smaller taxonomic groups also had a strong allometric relationship between diving capacity (maximum depth and duration) and body mass. Notable exceptions were mysticete cetaceans and diving/flying birds, which displayed no relationship between maximum diving depth and body mass, and otariid seals, which showed no relationship between maximum diving depth or duration and body mass. Within the diving/flying bird group, only alcids showed a significant relationship (r = 0.81, n = 9 for depth). The diving capacities of penguins had the highest correlations with body mass (r = 0.81, n = 11 for depth; r = 0.93, n = 9 for duration), followed by those of odontocete cetaceans (r = 0.75, n = 21 for depth; r = 0.84, n = 22 for duration) and phocid seals (r = 0.70, n = 15 for depth; r = 0.59, n = 16 for duration). Mysticete cetaceans showed a strong relationship between maximum duration and body mass (r = 0.84, n = 9). Comparisons across the various groups indicated that alcids, penguins, and phocids are all exceptional divers relative to their masses and that mysticete cetaceans dive to shallower depths and for shorter periods than would be predicted from their size. Differences among groups, as well as the lack of relationships within some groups, could often be explained by factors such as the various ecological feeding niches these groups exploit, or by variations in the methods used to record their behavior.

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 16ЊC. 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 durations were intended to simulate the conditions faced by fish that were either easy or difficult to remove from the hook. Fish experienced arrhythmia during angling, although overall cardiac output increased. Fish experienced severe bradycardia during air exposure, but after being returned to the water, all fish exhibited elevated cardiac output. Fish exposed to 30 s of air exposure required 2 h for full recovery, whereas those exposed to 180 s of air required 4 h. During periods of cardiac disturbance, increases in cardiac output were due to both heightened heart rate and stroke volume. Our results suggest that hooking mortality did not vary with bait or hook type and that physiological disturbance of rock bass was influenced by the duration of air exposure, as influenced by bait and hook choice. We recommend that anglers attempt to minimize handling and air exposure of angled fish and keep pliers or other hook removal devices readily accessible to facilitate rapid release of fish not intended for harvest.

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 dive). Comparative analyses across these dive types and the different species revealed that square dives were always, and by far, the most abundant dive type, usually followed by V dives, and then the skewed dives. The percentage of time that the animals spent at the bottom of square dives (∼50%), as well as the variation in depth during this bottom time (∼15%) were also quite uniform across species, indicating that similar foraging patterns were being used, at least relative to the shape of dives. Observed differences across species revealed that larger divers generally dived deeper and longer than did smaller ones, although fur seals and walrus were exceptions, with more limited diving performance than expected based on body size. Also, smaller divers had a tighter coupling between dive depth and duration than did larger ones, indicating that they may be more duration limited. Few other dive variables (e.g., the rate at which dive duration increases with depth, the percentage of dives within each dive type, the percentage of bottom time, the coefficient of variation of depth during bottom time, and the mean wiggle distance per depth during square dives) were affected by body size, but instead physical (water depth) and ecological (type of prey) constraints appeared to play major roles. Analyses using calculated aerobic dive limit (cADL) indicated that generic calculations are problematic and that estimates of diving metabolic rate can drastically influence cADL and resultant findings. However, even using crude estimators, comparisons of cADL across dive types indicated that square dives and V dives most often exceeded the cADL for large and small divers, respectively. This indicates that square dives and V dives may be the predominant foraging dive types for larger and smaller divers, respectively, as animals would be expected to push their limits most during this activity. However, the abundance of square dives within the small divers (>60%) indicates that these dives may have a foraging role as well. Function...

Most studies of pinniped diving behavior have manually grouped dives according to similarities in the depth, duration, and appearance of the dive profile. Dives of 15 adult female Weddell seals (Leptonychotes weddellii) were recorded with time‐depth recorders and 39, 119 dives were classified manually and statistically (principal components analysis, discriminant function analysis, cluster analysis, and shape‐fitting algorithms). Four dive types, common to all classification methods, and a fifth dive type, common to two of the methods, represented most of the observed diving behavior. However, a few variations of these dive types, specifically a flat‐bottomed dive determined manually, may have also represented important behavior. Using a combination of these methods, all dives were classified into six dive types, Inspection of dive variables (mean maximum depth, mean duration, and frequency) over time for each dive type, as well as comparisons to previous studies of pinniped diving behavior, indicated different behaviors that the dive types may represent. Hypothesized functions for the dive types were pelagic foraging, benthic foraging, exploration, and traveling. The results indicate that there are strong similarities in diving behavior across various phocid species, that statistical analyses of diving behavior are useful in the analysis of a large data set, and that these analyses reduced human subjective bias in interpreting diving behavior.

Catch‐and‐release angling of black bass Micropterus spp. during the parental care period may lead to brood predation and premature nest abandonment. Furthermore, physiological disturbance incurred while landing angled males may impair their ability to provide parental care long after release. To assess the extent of this physiological disturbance, we examined the relative energetic expenditures of nesting (N = 4) and nonnesting (N = 2) male largemouth bass Micropterus salmoides exposed to staged angling events in experimental ponds. Information on fish locomotion, through activity of the axial musculature, was remotely collected using electromyogram transmitters. During angling, nonnesting fish fought with a higher intensity, probably expending significantly more energy than did nesting fish. In addition, although the locomotory activity of nonnesting fish appeared to recover as early as 2 h after angling release, the locomotory activity of nesting fish was still impaired 24 h postangling. Overall mean activity for 24 h postrelease was 98% of basal for nonnesting fish, but only 63% for nesting fish. The reduced energetic capability of a nesting male largemouth bass following angling, together with brood predation incurred as a result of the temporary removal of that fish from the nest during angling, increases the likelihood of that male abandoning his brood prematurely. This study provides further insight into the physiological disturbances and behavioral consequences incurred as a result of catch‐and‐release angling and highlights the need for addressing population level effects of catch‐and‐release angling on parental care and reproductive success of black bass.

Stable isotopes have become powerful tools for gathering information on food webs in marine ecosystems. The method is based on the concept that the ratio of Nitrogen‐14 to 15N (or Carbon‐12 to 13C) in the tissues of animals is directly related to the ratio found in their diet. Vibrissae provide a time series of stable isotope data as tissue is laid down sequentially over time. Here we examine the growth rate of 283 mystacial (muzzle) vibrissae of four gray seals, Halichoeruas grypus, over a five‐month period to investigate their applicability for stable isotope diet analysis. The individual vibrissae did not grow at a constant rate during the study, Fifty‐nine actively growing vibrissae were modeled to quantify the growth pattern using a three‐parameter von Bertalanffy curve, with the parameters estimated using non‐linear mixed‐effects models. This model incorporated the inherent serial correlation of these data. The growth rate was 0.024 cm/d (95% CI = 0.019–0.030), the asymptotic length differed significantly by location (F3,56=9.64, P < 0.001), but no significant trend was found with muzzle location (F3,56= 0.15, P= 0.93). The Δlength/Δtime between each measurement was calculated and most of these data fell at or near zero growth (median = 0.04 cm/d, range = 0–0.78). Individual vibrissae were shed asynchronously and without any seasonal growth trend. This has serious implications for researchers attempting to extrapolate diet data from vibrissae. Because the growth is neither continuous nor synchronous, it will be a challenge to accurately identify the dates when the isotopes were incorporated into the tissue.

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 ϭ 31) were acclimated to 12, 16, or 20ЊC 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 ϳ 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 ϳ 40 min) for briefly angled fish and from 20 to 210 min (mean ϳ 105 min) for exhaustively angled fish. These recovery times increased significantly with angling duration but were not affected by water temperature. Almost all of the increase in CO during recovery was attributable to increased HR. At 20ЊC, the increase in HR was sufficient to result in an increase in CO despite a decrease in SV during the initial portion of recovery. During recovery, both CO and HR increased to approximately 1.8 times and as much as 2.65 times the resting values, whereas SV increased to approximately 1.2 times the resting value. At 20ЊC, SV typically decreased to 0.8 times the resting value for the initial part of recovery. Recovery intensities (maximum increases in cardiac values) were generally not affected by angling duration. Fish acclimated to 16ЊC generally had larger recovery intensities than fish at 12ЊC and 20ЊC, indicating that for smallmouth bass, 16ЊC may be an optimal temperature relative to the other two temperatures. From a management perspective, the results suggest that (1) angling duration should be minimized, (2) angling at high as well as low temperatures may be detrimental, and (3) even when fish are angled very quickly, they still undergo a period of increased CO that can last as long as 1 h.

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 increased 150–200% relative to resting values despite 50% reductions in stroke volume, suggesting that largemouth bass are primarily frequency modulators. Maximal changes generally increased with water temperature for cardiac output and heart rate but not for stroke volume, resulting in heightened scope for cardiac output and heart rate with increasing water temperature. Recovery patterns were not influenced by water temperature. Cardiac output and heart rate generally returned to predisturbance levels in approximately 135 min, whereas stroke volume recovered more rapidly (about 110 min). Based on these findings, we suggest that largemouth bass exposed to exhaustive exercise and brief air exposure are capable of recovering from handling disturbances in several hours across the range of water temperatures that we examined (13–25°C).