Preliminary hematology and biochemistry reference intervals in juvenile blacktip sharks (Carcharhinus Limbatus) in the GalaPagos Marine Reserve

Species-specific hematology and biochemistry reference intervals (RIs) provide a crucial diagnostic resource for veterinarians, researchers, and wildlife managers working with elasmobranchs. This study aimed to establish hematologic and biochemical RIs from a population of free-ranging, juvenile blacktip sharks (Carcharhinus limbatus) in the Galápagos Marine Reserve in Ecuador. Heparinized blood samples were collected from the ventral coccygeal vein in 36 juvenile blacktip sharks captured via beach seine and physically restrained. Manual CBCs were performed, and heparinized plasma was submitted to a reference laboratory for biochemistry analysis. Per American Society for Veterinary Clinical Pathology guidelines, preliminary hematology and biochemistry RIs were determined minus white blood cell differentials due to artifact following blood smear storage and transport. Juvenile blacktip sharks in the Galápagos Marine Reserve had similar PCV (median: 28%, RI: 18.6-35%) but higher WBC concentrations (median: 29.9 × 10³/μL, RI: 9.5-52.4 × 10³/μL) than wild adult sandbar sharks (Carcharhinus plumbeus). Furthermore, juvenile blacktip sharks had lower plasma concentrations of aspartate aminotransferase (AST, median: 6 U/L, RI: 4-13 U/L), creatine kinase (CK, median: 16 U/L, RI: 6-90 U/L), and glucose (median: 58 mg/dL, RI: 39-78 mg/dL) than wild Atlantic sharpnose (Rhizoprionodon terraenovae) and bonnethead sharks (Sphyrna tiburo) may have been due to different capture methods. Hematology and biochemistry reference intervals will aid blacktip sharks under managed care and support future comparative and longitudinal research of blacktip shark populations within the Galápagos Marine Reserve.