Francis G. Carey

Movements of blue sharks (Prionace glauca) in depth and course

Acoustic telemetry was used to follow 22 blue sharks,Prionace glauca (Linnaeus), over the continental shelf and slope in the region between Georges Bank and Cape Hatteras between 1979 and 1986. The sharks frequently made vertical excursions between the surface and depths of several hundred meters. The oscillations, which were repeated every few hours, were largest in the daytime and were smaller in amplitude and confined to depths near the thermocline at night. This behavior was prominent in trials from August through March, but was not seen from June through July. Diving is discussed in terms of a hunting tactic and behavioral thermoregulation. Most of the sharks moved in a southeasterly direction from the release point and many maintained a constant course day and night for several days. The sharks may orient to the earths magnetic field, or to the oceans electric fields, allowing them to swim on a constant heading in the absence of celestial cues. These possibilities are discussed in the appendix.

Temperature regulation in free-swimming bluefin tuna☆

Abstract 1. 1. Acoustic telemetry was used to monitor ambient water temperature and tissue temperature in free-swimming bluefin tuna ( Thunnus thynnus Linneaus, 1758) over periods ranging from a few hours to several days. 2. 2. Bluefin, which experienced marked changes in water temperature, showed excellent regulation of the temperature of the stomach and epaxial muscles. 3. 3. Other species, bigeye tuna ( Thunnus obesus Lowe, 1893) and dusky shark ( Carcharhinus obscurus Lesueur, 1818) did not appear to control their body temperatures. 4. 4. The bluefin does not have a fixed temperature set-point: fish taken from the same school may vary 5°C or so in their maximum muscle temperature, and on occasions the body temperatures of fish we followed were observed to change independently of water temperature.

Regulation of body temperature by the bluefin tuna

Abstract Bluefin tuna (Thunnus thynnus Linnaeus) can control the temperature of their bodies (25–30°C) so that the warmest portion of the muscle mass varies only 5°C over a 10°C–30°C range of water temperature.

Vertical and horizontal movements of striped marlin (Tetrapturus audax) near the Hawaiian Islands, determined by ultrasonic telemetry, with simultaneous measurement of oceanic currents

We measured the vertical and horizontal movements of striped marlin (Tetrapturus audax) off the leeward coast of the Island of Hawaii between 20 November and 18 December 1992 while simultaneously gathering data on water temperature and oceanic currents. Fish movements were monitored by ultrasonic depth-sensitive transmitters, depth-temperature profiles by an expendable bathythermograph system, and oceanic current patterns by an acoustic Doppler current profiler. Like Indo-Pacific blue marlin (Makaira mazara), striped marlin near Hawaii spend >85% of their time in the mixed layer (i.e., above 90 m depth). The maximum depth for striped marlin appears to be limited by water temperatures 8 C° colder than the mixed layer, rather than by an absolute lower temperature. We also found that the horizontal displacements of some striped marlin can be strongly influenced by currents.

Mako and porbeagle: warm-bodied sharks.

Abstract 1. 1. Mako and porbeagle sharks are able to conserve metabolic heat and maintain their bodies 7–10°C above ambient temperatures. 2. 2. Highly developed countercurrent heat exchangers located in the vascular system of these fish form a thermal barrier which prevents heat from being carried off by the circulating blood and lost in the gills.

Temperature and Activities of a White Shark, Carcharodon carcharias

A large (4.6 m) white shark was followed for 3.5 days while its depth, water temperature and muscle temperature were recorded by acoustic telemetry. During this time the shark moved 190 km from an area south of Montauk Point, New York to Hudson Canyon. It made a number of brief excursions to the surface and to the bottom, but usually swam in the thermocline. Muscle temperature of the shark was as much as 5 C warmer than the water, confirming that a system of large retia mirabilia in the circulatory system function as heat exchangers. The shark did not thermoregulate and muscle temperature changed slowly as water temperature changed. The warming of the muscle as the shark swam into warmer water allowed us to estimate its rate of metabolism. The rate obtained is low and despite being warm, it appears that the shark can maintain itself for more than a month on a single large meal. The implications of this for its feeding habits are discussed.

Depth and temperature of the blue marlin, Makaira nigricans, observed by acoustic telemetry

Multiplex acoustic transmitters were used to monitor the depth, swimming speeds, body temperature and water temperature preference of six blue marlin, Makaira nigricans (Lacépède), near the Hawaiian islands in July and August 1989. The blue marlin ranged in size from 60 to 220 kg and were tracked for 1 to 5 d. All of the fish moved away from the point of capture and were followed up to 253 km from the island of Hawaii. The blue marlin tracked remained in the top 200 m of the water column, spending half the time in the upper 10 m, and rarely ventured below the thermocline. In the nearsurface waters the temperature was uniformly warm (25 to 27°C). The coldest water temperature, 17°C, was encountered on the deepest descent recorded (209 m). Depth changes occurred rapidly and excursions below 10 m were usually less than 60 min in duration. Muscle temperature was similar to water temperature except for a 2°C elevation in muscle temperature observed at the beginning of tracking one individual. This initial rise in body temperature was associated with the anaerobic muscle activity during capture and is an indication of the physiological stress involved in capture.

The Metabolism of Marsh Crabs under Conditions of Reduced Oxygen Pressure

low oxygen pressures when in their burrows. When exposed to such an environment they must alter their metabolism either by reducing it so that the oxygen supply is still sufficient for their needs or by converting from oxidation to fermentation. Various aspects of the respiration of the marsh crabs Uca pugnax, U. pugilator, and Sesarma cinereum in air and in aerated water have been studied by Tashian (1956), Teal (1959), and Vernberg (1959), among others. This paper is an investigation of the manner in which these crabs adapt their metabolism to periods of low oxygen.

Warm brain and eye temperatures in sharks.

Summary1.Temperatures in the brain and eyes of mako and porbeagle sharks (Lamnidae) are 5°C warmer than the water while the brain and eye temperatures in six other species of pelagic sharks are within 0.1°C of water temperature.2.An orbital rete mirabile is present in the porbeagle and mako sharks but absent in the cranial vasculature of eleven other species of pelagic sharks.3.The orbital rete in the head of the porbeagle and mako sharks acts as a heat exchanger which conserves metabolic heat and raises the local tissue temperatures.4.This brain and eye warming system should buffer the central nervous system from the effects of rapid temperature change. Warming of the retina may improve the visual sensitivity of these active predators.

The Visceral Temperatures of Mackerel Sharks (Lamnidae)

The viscera of mako Isurus oxyrinchus and porbeagle Lamna nasus sharks are significantly warmer than the water. The large suprahepatic rete mirabile in these fish is identified as a heat exchanger which retains metabolic heat to warm the visceral organs. An argument is presented that the efficiency of heat exchange in the rete must be greater than 97% to maintain the observed tissue temperatures and that this requirement explains the large size of the rete. A venous passage with a muscular wall which runs through the suprahepatic rete could allow blood to bypass the heat exchanger, and its presence suggests a simple mechanism for controlling temperature. However, measurements of temperature by acoustic telemetry from freeswimming sharks over a 4.5-day period do not give a convincing indication that stomach temperature is altered in a manner independent of the environment.