Howard E. Winn

Acoustic Discrimination by the Toadfish with Comments on Signal Systems

The oyster toadfish, Opsanus tau, produces two basic sounds which have a variety of properties. The grunt is made by both sexes, but more frequently by males during aggressive encounters in the reproductive season. The boatwhistle call is produced by males in long spontaneous sequences on their nests. They do so most often at the beginning of the mating season. Individual grunts are sometimes spontaneously interspersed between boatwhistles. It is thought by Fish (this volume) and Winn (1967) that some of these are incomplete boatwhistles. Males increase their boatwhistle calling when boatwhistles are played back at certain rates (Winn, 1967). It was this response that was utilized by Fish (this volume) to elucidate the properties of pattern, interval, cycle time, and antiphony in O. tau. Here I will describe the physical parameters of the boatwhistle call, such as frequency, amplitude, rate, and duration, that result in vocal facilitation. These will be generally discussed in relation to the development of acoustic signal systems in fishes.

Song of the humpback whale — Population comparisons

SummaryHumpback whale songs recorded on tropical calving grounds exhibit different dialects depending on the oceanic basin. Songs sampled simultaneously from two populations in the North Pacific (Hawaii and Mexico) were essentially identical. These North Pacific songs were clearly different from the song type shared by two populations in the North Atlantic (Cape Verde Islands and West Indies). Songs from the Southern Hemisphere (Tonga) represent a third distinct dialect. Our evidence shows that, despite annual change in song organization, significant differences in humpback song occur between isolated ocean basins, while only subtle differences exist within an oceanic population (Hawaii and Pacific Mexico).

Cetaceans in the Great South Channel, 1979–1989: right whale (Eubalaena glacialis)

A continuous 11-year time-series of aerial and shipboard survey data in the Great South Channel region reveals a remarkably consistent pattern of right whale distribution, with several interesting variations. Right whales occur in the area during the spring, with a distinct peak in May. Arrival and departure dates appear to vary by a month or more between years. The distribution is concentrated in the deeper basin north of the V-shaped 100-m isobath and a thermal front which approximately parallels the isobath. Within a single year, this concentration tends to be within a relatively small area and may remain stable for days or weeks. The center of distribution changes between years, and in 1984, 1987 and 1989 was on the eastern side of the basin rather than the “typical” western side. At any one time, nearly all of the right whales may aggregate into one to several clusters of <10 km2 each. A gradual southward shift in the center of distribution can be observed as the season progresses. Single-day abundance estimates, uncorrected for animals missed while submerged, ranged up to 179 animals. There was a statistically significant long-term increase in right whale sighting rates in the region, after correcting for estimated increases in survey efficiency, of 3.8% per year. This suggests that the population might be recovering, albeit slowly, from extreme depletion. It is likely that a significant proportion of the western North Atlantic right whale population utilizes the Great South Channel region as a feeding area each spring, aggregating to exploit exceptionally dense copepod patches.

Dive patterns of tagged right whales in the Great South Channel

Abstract Right whales were tagged in 1988 and 1989 with radio and sonic telemetry tags as part of a multidisciplinary investigation of right whales and their habitat in the Great South Channel region east of Cape Cod. The tags yielded data on the durations of 6456 dives and 6482 surfacings, as well as 23,538 measurements of the depth of a diving whale. Log-survivorship analysis of the 1988 data showed a clear separation between the durations of dives between blows within a single surfacing sequence or bout (intea-bout dives) and longer dives between surfacing sequences (interbout dives) at 27 s, which was also applied to the 1989 data. Inter-bout dives averaged 127.3 s, and were significantly longer in 1988 than in 1989. Inter-bout dives were significantly longer during the day than night in 1988, and longer at night in 1989. The average intea-bout dive duration was 11.8 s, with 1989 dives longer than those in 1988. Surface durations averaged 6.2 s, and were also significantly longer in 1989. Dive depths were recorded only in 1989. Mean dive depth was 7.3 m, and only 12 dives went deeper than 30 m. The typical right whale dive pattern in 1988 included relatively short surfacings, long dives during the day, and shorter dives at night. This correlated with strong diel vertical migration by the dense zooplankton patches on which they were presumed to be feeding based on indirect evidence-from near the surface at night to near the bottom during the day. The 1989 pattern included longer dives during the night, as well as some exceptionally long surfacings. Zooplankton in 1989 did not migrate vertically, and remained near the surface day and night in right whale feeding areas. Right whale dive patterns in the Great South Channel are closely correlated with the horizontal and vertical distributions and movements of dense patches of their zooplankton prey.

Relationship between the distribution pattern of right whales, Eubalaena glacialis, and satellite-derived sea surface thermal structure in the Great South Channel

Abstract Right whales (Eubalaena glacialis) were sighted during random aerial transects over the Great South Channel region located between Georges Bank and Cape Cod in April to July in 1979–1981, 1984 and 1985. Sightings were superimposed on satellite AVHRR (Advanced Very High Resolution Radiometer) imagery of the same or approximate date to describe the whales distribution pattern in relation to the thermal front, the 100 m isobath and sea surface temperature (SST) characteristics within the region. The majority of whales occurred north of the thermal front in the warmer, more stratified waters of the Gulf of Maine. Within the Great South Channel region, whales are not limited to a given surface isotherm. As would be expected from a stratified water mass, SST at whale sightings in the Gulf of Maine did not differ significantly from the median SST of those waters, and the horizontal SST gradient at whale sightings was not higher than background values. The SST did differ significantly from the median SST of the entire area sampled. Whales are distributed non-randomly about, and are in close proximity to, the 100 m isobath and the thermal front. The results indicate that whales were not found in areas where surface signatures of upwelling on or at spatial scales greater than 1 km2 are present. The proximity of whale sightings to the isobath and the front suggests that frontal features and/or associated phenomena play an important role in the distribution pattern of right whales in the Great South Channel region.

Locomotor Activity of the American Eel (Anguilla rostrata)

The locomotor activity cycle of the American eel (Anguilla rostrata) was studied in a light-proof shelter. Measurements of activity were registered by a mechanical assembly triggered by the eel’s movements. The results demonstrate that the eel posses a locomotor cycle with greater activity in dark than in light and activity peaks in response to light changes at dawn and dusk. The latter is significantly higher than any of the peaks during the night or the one at dawn. The one at dawn is frequently not any higher than some peaks of activity occurring throughout the night. The presence of peaks at dawn and dusk appears to be a more generalized condition than the period of maximum activity. Both frequency and phase of the eel’s cycle were shown to vary directly with the light conditions, and the cycle was totally obliterated under constant conditions of either light or dark. It is concluded that this locomotor activity cycle is essentially exogenous, under the control of the environmental light cycle, with the preference for dark activity being the only endogenous component.

Cetacean biomass densities near submarine canyons compared to adjacent shelf/slope areas

Estimated cetacean biomass densities in areas of the northeastern U.S. continental shelf edge encompassing major submarine canyons were compared to those in neighboring shelf/slope areas. It was hypothesized that biomass-densities would prove to be higher in the canyon areas: however, the analysis demonstrated significantly lower total cetacean biomass in the canyon areas. When species were analyzed individually, only spotted dolphins (Stenella spp.) showed a significant difference, with higher densities near the canyons. The canyons are apparently not more important as a cetacean habitat than the shelf break region generally.

Signature information in the song of the humpback whale

This report tests the hypothesis that individual humpback whales (Megaptera novaeangliae) can be recognized and discriminated from other individuals on the basis of the ’’cry’’ vocalization. Multivariate discriminant analyses, based on six measurable variables, were used to examine intra‐ and interindividual differences in the ’’cries’’ from several individuals. Cries between themes of one song are very different, whereas those between songs of one individual are similar. Results show a high degree of discriminating power between individual animals. Thus, signature information is potentially available from ’’cries’’ within songs, despite common song formats for all calling animals on a given bank. The statistical techniques used will be of great value in animal vocalization studies.

Sexual dimorphism and natural movements of the American eel(Anguilla rostrata) in Rhode Island streams and estuaries

KurzfassungDer Augendurchmesser männlicher Amerikanischer Blankaale(Anguilla rostrata) war beträchtlich größer als derjenige von Amerikanischen Gelbaalen. Blankaalmännchen hatten eine wesentlich geringere Durchschnittslänge als Blankaalweibchen. In kleinen Fließgewässern dominierten die Männchen, in Flußmündungen war der Weibchenanteil vergleichsweise größer. Die Abwanderung ins Meer fand hauptsächlich während der Monate September bis November statt und war verstärkt bei nennenswerten Regenfällen sowie während des dritten und vierten Mondviertels. Die Untersuchungen erbrachten in vieler Hinsicht ähnliche Ergebnisse, wie sie vom Europäischen Aal bekannt sind. Es wird angenommen, daß hinsichtlich der Stimuli für Beginn und Aufrechterhaltung der Laichwanderung eine große Zahl von funktionellen Sicherungen vorhanden ist, welche die Vermehrung gewährleisten.Summary1. The eyes of silver males were much enlarged, but not thoses of femaleAnguilla rostrata specimens.2. Silver males were smaller than silver females.3. Males predominated in freshwater and the proportion of females increased in estuaries.4. In trap catches from 1969 to 1972, most silver eel runs occurred from September through November and came after rains or in the third and fourth lunar quarters. More yellow eels are also caught at this time.5. Based on records from an electronic fish counter, silver eels moved primarily from just after sundown to 2300 hr.6. It is suggested that with regard to stimuli initiating migration, a great deal of redundancy is built into the system so that reproduction is assured.

Photogrammetric Estimates of Allometry and Calf Production in Fin Whales, Balaenoptera physalus

Fin whales ( Balaenoptera physalus ) from a census area on the outer continental shelf of the United States were measured photogrammetrically from vertical-aerial photographs taken in 1979 and 1980. Equations of allometric growth were developed that allowed prediction of total length from other body proportions such as snout-to-blowhole, snout-to-flipper insertion, and fluke spread. Annual rates of reproduction (28–55%) and annual rates of calf production (4−7%) were estimated for this population of fin whales, indicating a potential increase in size of the population.