Stomach contents of long-finned pilot whales (Globicephala melas) from southern Chile

The widely distributed long-finned pilot whale (Globicephala melas) has been reported off the Chilean coast, from Iquique (20°12′S) south to Navarino Island (55°15′S; 67°30′W), but little is known about its biology or ecology in the region. Here, we report on the prey of this species, identified by stomach content analyses from animals stranded on Holget Islets, Beagle Channel, southern Chile in August 2006. The stomachs of seven individuals (six females and one male) contained cephalopod remains. The prey composition found in these southern Chilean pilot whales was similar to that described in other parts of the world and the Southern Ocean. This is the first report on the feeding habits of this species from Chile.     

Stomach contents of mass-stranded short-finned pilot whales (Globicephala macrorhynchus) from North Carolina

We examined the stomach contents of 27 short‐finned pilot whales (Globicephala macrorhynchus) that mass stranded on the North Carolina coast on 15 January 2005. Eleven whales had prey parts in their forestomachs. We used frequency of occurrence and numerical abundance to assess the relative importance of prey. Brachioteuthis riisei (numerical abundance 28%), an oceanic species, was the most important cephalopod prey, but Taonius pavo (12%) and Histioteuthis reversa (9%) also represented a substantial part of the diet. A large number of otoliths belonging to the fish Scopelogadus beanii were present (25%). These results differ from reports of the stomach contents of short‐finned pilot whales from the Pacific coast in which neritic species dominate the diet. Our findings also suggest that there is a considerable difference between the diet of short‐ and long‐finned pilot whales (Globicephala melas) in the western North Atlantic. The latter feed predominantly on the long‐finned squid (Loligo pealei) whereas the former feed on deep‐water species. Our results indicate the whales fed primarily off the continental shelf prior to stranding.     

Occurrence of long-finned pilot whales (Globicephala melas) and killer whales (Orcinus orca) in Icelandic coastal waters and their interspecific interactions

acta ethologica - Long-finned pilot whales and killer whales are widely distributed across the North Atlantic, but few studies have reported their occurrence in Icelandic coastal waters. Here, we...     

Life history and group composition of melon‐headed whales based on mass strandings in Japan

We examined melon‐headed whales that mass‐stranded live in two events in Japan: (1) 171 animals at Tanegashima Island in 2001 and (2) 85 animals at Hasaki in 2002. We report here the results of life history traits and group composition of these strandings, and compare them to another mass stranding with 135 individuals at Aoshima in 1982. In the Hasaki event, most stranded animals, including those released were sexed and measured. The proportion of live males released was much higher than that of females, and larger animals, especially females, were more likely to have died. Females were estimated to attain sexual maturity at around 7 yr and give birth every 3–4 yr. The sex ratio was significantly different between the Hasaki and Aoshima events. Among dead specimens, females of various age classes were included in all strandings, while age distribution of males varied considerably among strandings. This suggests females show group fidelity while males move between groups. Asymptotic body length of females from Hasaki was significantly smaller than that from Tanegashima, suggesting that more than one population of melon‐headed whales exist off Japan.     

Two‐component calls in short‐finned pilot whales (Globicephala macrorhynchus)

Short‐finned pilot whales (Globicephala macrorhynchus) have complex vocal repertoires that include calls with two time‐frequency contours known as two‐component calls. We attached digital acoustic recording tags (DTAGs) to 23 short‐finned pilot whales off Cape Hatteras, North Carolina, and assessed the similarity of two‐component calls within and among tags. Two‐component calls made up <3% of the total number of calls on 19 of the 23 tag records. For the remaining four tags, two‐component calls comprised 9%, 23%, 24%, and 57% of the total calls recorded. Measurements of six acoustic parameters for both the low and high frequency components of all two‐component calls from the five tags were compared using a generalized linear model. There were significant differences in the acoustic parameters of two‐component calls between tags, verifying that acoustic parameters were more similar for two‐component calls recorded on the same tag than for calls between tags. Spectrograms of all two‐component calls from the five tags were visually graded and independently categorized by five observers. A test of inter‐rater reliability showed substantial agreement, suggesting that each tag contained a predominant two‐component call type that was not shared across tags.     

Aspects of the reproductive biology ofPollicipes pollicipes (Cirripedia; Lepadomorpha) from the southwest coast of Portugal

The pedunculated cirripedePollicipes pollicipes is of considerable economic importance in Portugal, particularly along the southwest coast. Current knowledge of its biology is poor, as evidenced by the paucity of available literature. This paper reports on the reproduction of twoP. pollicipes populations, Castelejo and Zavial, on the southwest coast of the Algarve. Differences in reproductive patterns between the two sites were minor and not statistically significant, despite differences in environmental conditions between the two sites. Adult animals carried fertilised eggs from April throughout September, and the percentage of individuals with egg masses correlated positively with air but not with sea water temperature. Brooding success was greater with average air temperature in excess of 14°C during months of strong upwelling and presumed food availability. Functional ovaries and testes are available in the population all year round but fertilisation does not appear to occur during the winter months. Reproduction ofP. pollicipes on the southwest coast of the Algarve appears closely linked to the upwelling phenomenon with the rate of deposition of gonadal tissue probably being determined by environmental temperature. The cues which determine the cessation of fertilisation remain to be investigated.     

Patterns and trends in the diet of long‐finned pilot whales (Globicephala melas) in the northeast Atlantic

There is little previous information on feeding habits of long‐finned pilot whales (Globicephala melas) in the northeast Atlantic. The present study analyzed stomach contents of pilot whales stranded in Portugal (n = 6), Galicia (northwest Spain) (n = 32), and Scotland (United Kingdom) (n = 10), from 1990 to 2011. These animals ranged from 213 to 555 cm in length (24 females, 19 males and 5 of unknown sex). The main prey identified were cephalopods of the families Octopodidae and Ommastrephidae, the former being numerically more important in Iberia (Portugal and Galicia) and the latter more important in Scotland, with Iberian whales also showing a more diverse diet. Multivariate analysis revealed evidence of geographical and seasonal variation in diet. Generalized Additive Modeling results indicated that more octopus (Eledone cirrhosa) were eaten in Iberia than in Scotland, more in the first half of the year, and more in larger whales. Numbers of ommastrephid squids in the stomach decreased over the study period and varied with season and whale length. This study confirms cephalopods as the main prey of pilot whales, as previously reported, although our results also suggest that, in the northeast Atlantic, ommastrephid squid are largely replaced as the main prey by octopods at lower latitudes.     

Aspects of the biology of Hyolitha (Mollusca)

Hyolitha constitute an extinct group of class rank assigned to Molhsca. Two orders, Ortho-thecida and Hyolithida, are well established and most knowledge of morphologic detail is derived from the latter. Both orders had an operculum not hinged to the conch. Hyolithida also had paired, curved, whiskerlike appendages, requiring complex musculature to move them and the operculum. The Hyolithida were probably deposit feeders living in shallow water, and accordingly were tentaculate. A reconstruction of the soft parts of this sedentary organism is given — a shallow mantle cavity on the dorsal side, anterior tentacles, a long intestine, and a reduced ventral foot. Except for the more complex musculature associated with an elaborate operculum, Orthothecida are judged to have had a similar anatomy.     

Trends in the strandings of Cetacea on the British Coasts 1913-72

Records of Cetacea stranded on the British coasts have been maintained in the British Museum (Natural History) since they were started in 1913. Investigations have now been made into the possibility of trends of developments in these strandings. The data have been arranged in groups appertaining to 5-year periods for all species combined, round the entire British coastline, also in relation to the coast on which the animals were stranded. For this purpose the coast of Great Britain has been divided into three separate areas. In addition, three species have been selected and treated separately to demonstrate the different trends.
The frequency of strandings appear to be correlated with the abundance of food fish, this in turn being related to the planktonic and nutritional values of the sea. There are one or two exceptions to this hypothesis, and it is suggested that there may be a correlation between an increase in strandings and a high mortality rate due to a lack of food fish.     

Fatal Asphyxiation in Two Long-Finned Pilot Whales (Globicephala melas) Caused by Common Soles (Solea solea)

Long-finned pilot whales (Globicephala melas) are rare visitors to the southern North Sea, but recently two individual strandings occurred on the Dutch coast. Both animals shared the same, unusual cause of death: asphyxiation from a common sole (Solea solea) stuck in their nasal cavity. This is a rare cause of death in cetaceans. Whilst asphyxiation has been reported in smaller odontocetes, there are no recent records of this occurring in Globicephala species. Here we report the stranding, necropsy and diet study results as well as discuss the unusual nature of this phenomenon. Flatfish are not a primary prey species for pilot whales and are rarely eaten by other cetaceans, such as harbour porpoises (Phocoena phocoena), in which there are several reports of asphyxiation due to airway obstruction by soles. This risk may be due to the fish’s flexible bodies which can enter small cavities either actively in an attempt to escape or passively due to the whale ‘coughing’ or ‘sneezing’ to rid itself of the blockage of the trachea. It is also possible that the fish enter the airways whilst the whale is re-articulating the larynx after trying to ingest large, oddly shaped prey. It is unlikely that the soles entered the airways after the death of the whales and we believe therefore that they are responsible for the death of these animals.     

Different modes of acoustic communication in deep‐diving short‐finned pilot whales (Globicephala macrorhynchus)

Toothed whales use a pneumatic sound generator to produce echolocation and communication sounds. Increasing hydrostatic pressure at depth influences the amplitude and duration of calls but not of echolocation clicks. Here we test the hypothesis that information transfer at depth might be facilitated by click‐based communication signals. Wild short‐finned pilot whales (27) instrumented with multisensor DTAGs produced four main types of communication signals: low‐ and medium‐frequency calls (median fundamental frequency: 1.7 and 2.9 kHz), two‐component calls (median frequency of the low and high frequency components: 2 and 9 kHz), and rasps (burst‐pulses with median interclick interval of 21 ms). Rasps can be confused with foraging buzzes, but rasps are shorter and slower, and are not associated with fast changes in body acceleration nor reduced acoustic output of buzzes, characteristic of prey capture attempts. Contrary to calls, the energy flux density of rasps was not significantly affected by depth. This, and a different information content, may explain the observed increase in the relative occurrence of rasps with respect to calls at depth, and supports the hypothesis that click‐based communication signals may facilitate communication under high hydrostatic pressure. However, calls are produced at depth also, indicating that they may carry additional information relevant for deep‐diving animals, including potential communication among whales diving at the same time in this highly social deep‐diving species.     

Aspects of the population biology of Cephalopholis fulva from the central coast of Brazil

Age and size composition samples of Cephalopholis fulva from the central coast of Brazil were collected from research surveys and from line fishery landings between 1997 and 1999. The samples suggest that the submarine banks located further offshore are characterized by having fish larger than those caught in the continental shelf area. Although the oldest specimens were caught in the continental shelf area, only 34.6% of the specimens were older than 10 years as compared to 51.4% in the submarine banks. The observed size and age differences seem to be related to the lower fishing pressure on the submarine banks, although size composition bias resulting from different sampling procedures and different catchability between sites cannot be excluded. A resampling scheme was used to overcome the influences of size composition bias and to generate a three-dimensional plot of parameters as a means to compare the growth between the submarine banks and the continental shelf area; this plot showed no overlap between growth patterns of the two sites. The natural mortality ( M ) estimate based on the oldest specimen observed was 0.17 year⁻¹. Total mortality ( Z ) estimated from catch-curve analyses using samples from both areas varied from 0.24 to 0.34 year⁻¹, depending on the age range used. With this level of mortality, the C. fulva stock in the central coast area of Brazil was close to or already at the level of overexploitation in the late 1990s.     

Aspects of the biology of the pygmy ribbontail catshark Eridacnis radcliffei (Proscylliidae: Carcharhiniformes) from the south-west coast of India

Biological data are presented for the pygmy ribbontail catshark Eridacnis radcliffei based on specimens collected from the by-catch of the commercial deep-sea shrimp trawl fishery operating in the Arabian Sea off the south-west coast of India. A total of 549 individuals, from 101 to 257 mm total length (L(T) ) and 2·2 to 56 g, were collected. The L(T) at first maturity (L(T50) ) of females and males was estimated at 183 and 170 mm, respectively, and analysis of stomach contents revealed that E. radcliffei feeds primarily on crustaceans.     

Aspects of the biology of Scomberomorus maculatus (Mitchill) in Trinidad

A study was made of the biology of S. maculatus . Results of gonadal examination of 347 males and 409 females suggest spawning takes place from October to April, a period associated with low salinities. First spawning takes place at ages I1 and/or III for both sexes. Sex ratio results suggest spawning may be promiscuous, males outnumbering females. Egg counts from 12 ripe females ranged from 26 057 to 149 736. A period of abundance from May to September may be associated with a post-spawning feeding migration encompassing the island, possibly in a clockwise direction. Otolith were used to age 817 fish. Opaque and translucent rings are formed yearly. The translucent ring, representing a period of slow growth, is laid down during the spawning season. The fish can live for nine years with females growing faster than males. Growth parameters are compared with those obtained for Brazilian and Florida fish. Mortality rates were investigated and gill nets effected higher mortality rates than beach seines. Full recruitment takes place at age III for gill nets, and ages II and III for beach seines.     

Aspects of the reproductive biology of Gonostoma bathyphilum (Gonostomatidae)

Protandrous hermaphroditism among deep-sea fishes is known only within one family, Gonostomatidae, and therein restricted to a few species of two genera, Cyclothone (C. atraria, C. microdon) and Gonostoma (G. elongatum, G. gracile). Gonostoma bathyphilum, the deepest dwelling (700–2700 m depth) of Gonostoma spp., is also protandrous and shares with Cyclothone spp. an expression of sexual dimorphism manifested by the excessive development of olfactory structures, including the olfactory lobes, in ripe males. Sex-reversal in ripe males, therefore, involves a regression of these structures. The relationships apparent between sex, maturity and olfactory development, and those between animal size, maturity and depth of occurrence, indicate that whilst protandry is an integral component of the species' reproductive strategy some individuals develop directly as females and that among males (max. size 150 mm S.L.) sex-reversal is not obligatory. Primary females, together with those derived from prematurely reversing males, may form an early maturing female group, spawning for the first time at about 110–120 mm S.L. Most hermaphrodites were < 100 mm S.L., and within the 70–99 mm S.L. size-range a significant proportion had mature male characters. Since males of this size were all found to be immature, this suggests that these hermaphrodites are derived from a precocious element within the initial male population, and, by virtue of size-stratification by depth, are responsible for mating with the early-maturing females. The lack of a marked seasonality in the sexual cycle implies an ever presence of all sexual categories within the population. It is conjectured that sex-reversal of ripe males is a response to critical population density levels of ripe females and that the smaller, precocious males would be more prone to sex-reversal than the larger, later-maturing ones. In some respects protandry in G. bathyphilum is similar to that in G. elongatum. In the latter, however, the reproductive cycle is seasonally linked and sex-reversal in males is probably obligatory. Even so, critical density levels of ripe females can still be invoked as being causal to sex-reversal.