Biology of Finfish and Shellfish (2+1)

Hemiramphidae

• Larvae elongate to very elongate, squarish in cross-section to moderately compressed, with 51-57 myomeres (35-40+15-19).
• The gut is relatively thick, straight and long, and reaches to about three-quarters of BL.
• The conspicuous gas bladder is located over the anterior half of the gut. Snout length remains relatively constant (2-5%BL) but the lower jaw increase in length: 3-7%BL in larvae less than 6mm; 25-74% in larvae around 20mm.
• Unfortunately, the elongate lower jaw of larval hemiramphids is fragile.
• Very small, pointed teeth are present on both jaws in the smallest specimens.
• The eye is slightly elongate. Larvae hatch with a well-developed caudal fin: most caudal fin rays are ossified at hatching.
• The dorsal and anal fins are situated far back on the body and have subdivided in the smallest specimen.
• Pectoral rays first appear between 5.4 and 6.1 mm, and they are all ossified by 13mm.
• Small pelvic-fin buds appear well-back on the body at 8-12mm; incipient rays develop from 10mm, and full fin complements are present by 13mm.
• Hemiramphid larvae are moderately to heavily pigmented. Discrete longitudinal rows of melanophores are characteristic, primarily dorsally and sometimes ventrally, on the trunk and tail.
• Pigment may also occur on the dorsal surface of the head, both jaws, opercle, gut, urostyle, and later on caudal fin rays and bases, and posterior lobes of the dorsal and anal fins.