Differences in hematocrit of blood samples obtained from two venipuncture sites in sharks

Abstract

T he field of elasmobranch medicine is in its infancy, and there is a paucity of information on hematologic values 1-4 despite the growing need for veterinary care of cap-tive sharks. Sites for collection of blood samples in sharks are typically chosen in accordance with the method of animal handling. When a shark is large or difficult to manually restrain, it is most convenient to obtain a blood sample from the dorsal sinus, an area located at the caudal aspect at the base of the dorsal fin. This method allows handlers to maintain the shark in ventral recumbency. When a shark is easily restrained or anesthetized, blood collection from the caudal tail vein or artery is usually chosen because the shark can be placed in dorsal recumbency, which facilitates access to the vessels. In the authors' clinical experience, Hcts differ in samples collected from these 2 sites for use in routine health screening of captive shark populations. To assess the importance of this observation, a prospective study was initiated that used both captive habituated sharks and captured free-ranging (wild) sharks.Sharks can be classified into metabolic categories on the basis of their method of respiration. Pelagic sharks (ie, open-water sharks) rely on ram ventilation. These sharks ensure ventilation by forcing water over their gills and, hence, are obligated to swim constantly. Conversely, nonpelagic sharks (ie, reef-oriented species of sharks) are capable of pumping water over their gills and can rest on the ocean bottom for extended periods. The nonpelagic species have a higher tolerance for anaerobic situations than do the pelagic sharks. 5,6 The Hct in tuna, a high-energy, ram-ventilating teleost, is considerably higher than the Hct in most other teleosts because tuna have a high requirement for oxygen. 7 Therefore, we elected to assess whether similar differences existed in pelagic and nonpelagic sharks. Materials and MethodsAnimals-Blood samples were collected from 47 adult sharks. The sharks comprised 2 groups (32 captive habituated sharks and 15 captured free-ranging wild sharks). Sharks were considered adults on the basis of secondary sex characteristics; standard and total length measurements; and, when possible, body weight.Collection of blood samples-Captive habituated adult sharks were acclimated to captive conditions for at least 1 year, and all were handled or anesthetized during that time period. Samples were obtained twice from some sharks. Animals included 4 brown sharks (Carcharhinus plumbeus), 13 blacktip reef sharks (Carcharhinus melanopterus), 3 wobegong sharks (Orectolobus japonicus), 4 zebra sharks (Stegastoma fasciatum), and 8 whitetip reef sharks (Triaenodon obesus). All sharks were considered healthy on the basis of results of physical examination, routine hematologic tests, and serum biochemical analysis, as determined by use of in-house reference ranges.Objective-To evaluate differences in Hct between 2 venipuncture sites in captive and free-ranging sharks. Animals-32 healthy adult captive sharks (Carcharhinu...

Natural or Artificial? Habitat-Use by the Bull Shark, Carcharhinus leucas

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Fish Hematology and Associated Disorders

“…The PCV tends to be lower in samples collected from the venous sinus near the dorsal fin than from those collected from the caudal vein of the tail. 29,30 Other factors that may contribute to PCV variation in healthy animals include stress (handling, anesthesia, water intake), physical characteristics (size, species), sex, environmental factors (water temperature, dissolved oxygen, population density, photoperiod), activity level (thermodynamics), reproductive status, life stage, and diet. Anemia is classified as hematocrit less than 20%, and may be due to blood loss (hemorrhagic anemia), cell destruction (hemolytic anemia), or decreased production (hypoplastic anemia).…”

Comparison of hematology, plasma biochemistry, and blood gas variables between 2 venipuncture sites in Southern Stingrays (Dasyatis americana)

“…Hematologic and biochemical results may differ depending on the site of blood collection in many species, including nonbatoid elasmobranch species or sharks . Two venipuncture sites are commonly used in sharks: the caudal vasculature that runs along the ventral midline aspect of the tail, and the dorsal sinuses located immediately caudal to the dorsal fins .…”