Shallow Dives Research Articles

Food and feeding ecology of emperor penguins in the eastern Weddell Sea

The diet of the emperor penguin Aptenodytes forsteri in the eastern Weddell Sea, Antarctica was studied during October and November 1986 by stomach content analysis. Emperor penguins fed mainly on Antarctic krill Euphausia superba, Antarctic silverfish Pleuragramma antarcticum and squid Psychroteuthis glacialis. Benthic prey was not found. The prey composition suggests two different feeding strategies, shallow dives exploring the rugged underside of sea ice where krill is taken, and deep dives when mesopelagic fish and squid are consumed. Chicks were fed on average every 1.44 days.

Diving behaviour and prey of the Humboldt Penguin (Spheniscus humboldti)

Humboldt Penguins diving in clear water in Chile had two distinct behaviours; short dives\((\bar x = 13.3 s)\) where the birds remained within a metre of the surface and bounce dives, where the penguins descended the water column to the sea bed where they immediately returned to the surface. Here, dive time was correlated with water depth. Stomach pumped penguins had eaten predominantly pelagic school fish,Scomberesox, Engraulis andSardinops. Most prey (94 %) had been seized from below. We suggest that short, shallow dives are typical of travelling penguins. Bounce dives, however, would enable foraging penguins, which have an enhanced binocular field above the line of the bill, to perceive surface-swimming prey more easily because silvery clupeid fish appear as silhouettes.

Fur Seal Diving Behaviour in Relation to Vertical Distribution of Krill

(1) Quantitative studies of predator-prey interactions depend on a knowledge of their spatial dynamics and behaviour. Studies on marine vertebrates have hitherto been precluded by the difficulty of acquiring the relevant data. (2) Continuous records of diving depths of female Antarctic fur seals on 3-8 day feeding trips to sea from South Georgia were analysed in conjunction with data on diel changes in the abundance and distribution of their main prey, krill. (3) In 36 complete days foraging by seven seals, 75% of 4273 dives were at night. Dives then were consistently shallower (dive depth < 30 m) than in daytime (mostly 40-75 m). (4) This closely matched changes in the vertical distribution of krill, nearly all of which was below a depth of 50 m from 09.00-15.00 h, with substantial quantities above 40 m only between 21.00-06.00 h. (5) Although over 40% of krill in the water column at any time of day was below 75 m, only 3% of dives exceeded this depth. We suggest that because krill migrate vertically fur seals are able to exploit them most efficiently during shallow dives at night.

Blood and blood vessel wall changes induced by decompression sickness in dogs.

Healthy female dogs of mixed breed were anesthetized with pentobarbital sodium and given 51Cr-labeled autologous red blood cells and 125I-labeled anticanine vessel wall fiber (collagen and elastin) antibody. The anesthetized dogs were exposed to the equivalent of a 220-ft dive on air for 40-45 min (descent rate 75 ft/min, ascent rate 60 ft/min). The animal's condition was adjusted by additional shorter and/or shallower dives. Four dogs had mild decompression sickness (DCS), and seven had severe DCS judged by electrocardiogram. Three of the seven died before completion of the experiment. Permeability of the endothelial sheet of jugular veins and carotid arteries to the tracer (125I-gamma-globulin) was significantly increased in animals with severe but not mild DCS. There was slight hemoconcentration (increased capillary and venular permeability). Scanning electron microscopy showed that the endothelium was grossly intact with no evidence of mechanical damage, but giant cells (derived from monocytes) frequently adhered to the endothelium. Leukocytes and platelets adhered occasionally. Fibrin monomer was found in the plasma. Thus DCS is accompanied by endothelial cell alteration and limited blood cell adhesion to vessel walls in addition to activation od the clotting mechanism.

On the effect of moonlight on starch

Bulwer's petrels are nocturnal seabirds that mostly prey on mesopelagic fauna. As aerial foragers and shallow divers, their feeding opportunities are limited by near-surface availability of their prey, which is highly variable both temporally (reflecting diurnal and lunar cycles) and spatially. Here we studied how Bulwer's petrels cope with these constraints by analysing their at-sea distribution and activity during the incubation period. We tracked the movements of 20 birds from Selvagem Grande (NE Atlantic) during a complete lunar cycle, and recorded 30 foraging trips that lasted 11 days on average. Birds were both distributed around the colony and in waters close to the Azorean archipelago (mid-Atlantic) located 1700 km away, and were significantly more active at night (especially just after sunset and before sunrise), when mesopelagic fauna is also closer to the sea surface due to their diel vertical migrations. Bulwer's petrels spent significantly more time flying during moonlight, although the effect of the moon was relatively weak (ca. 10–15% difference between moonlit and dark periods of the night), and not obvious when birds were foraging in mid-Atlantic waters, which were also targeted more often during full-moon. These results reveal key adaptations of the Bulwer's petrel to the highly dynamic ecology of its mesopelagic prey.

Blood nitrogen tensions of seals during simulated deep dives

Blood nitrogen tensions of seals during simulated deep dives

Skin diving injury.

In his paper on the physiological and otolaryngological aspects of skin diving, Fields 1 described a diver who developed a neural hearing loss following a shallow dive of short duration. He added that he had not found a satisfactory explanation for the occurrence of the hearing loss. A similar accident and problem are presented. Report of Case A youth, aged 18, was first examined on July 2, 1959, with complaints referable to the left ear: mild pain, tinnitus, and deafness. Five days earlier he had been diving with a SCUBA. His descent was to about 35 feet when he felt pain in his ears and could not equalize. He rose to 20 feet, cleared his ears, and returned to the original depth for a short time. He again returned to 20 feet and terminated the swimming period after 30 minutes. Upon surfacing he noted ringing of the left ear. After

Skin Diving: Its Physiological and Otolaryngological Aspects

<h3>Definition</h3> Skin diving, as the term is now used, refers to the underwater sport of free diving, in which the participant wears a face mask and rubber flippers. Free diving implies that the diver is unencumbered by air or life lines extending to the surface. The sport has several ramifications, among which are spearfishing, photography, and exploration. In general skin divers are amateurs; however, there are a few professionals who teach the sport and market the various items of equipment. Skin divers are divided into two groups: (1) those who carry a self-contained air or oxygen supply, and (2) those who depend on breath holding. The former are able to carry out deeper and more extensive dives, the duration of which is limited by the capacity of the gas supply. The latter, of necessity, must be content with shallow dives of short duration. <h3>History</h3> Prior to World War II skin