No abstract

Pigfish, Orthopristis chrysoptera, readily undergo vitellogenesis in captivity, but final oocyte maturation (FOM), ovulation, and spawning can be unpredictable. The objectives of this investigation were to assess the effects of various doses of Ovaprim ® (sGnRHa [salmon gonadotropin-releasing hormone analog] + domperidone) and human chorionic gonadotropin (HCG) on FOM, ovulation, and spawning in pigfish. Ovaprim dosages investigated were 0.25, 0.50, 1.00, and 2.00 mL/kg, which were injected into the dorsal musculature of female pigfish. Male pigfish received one half the dosage administered to females to ensure spermiation. HCG doses of 500, 1000, 2000, and 4000 IU/kg were administered to female pigfish, with male pigfish once again receiving half the female dosage. Eggs were collected over a 72-h period postinjection and enumerated and assessed for fertilization, hatching percentage, and survival to first feeding. Eggs and larvae were photographed and a suite of morphological parameters was determined. Hormone dose evaluations with pigfish showed that the low-dose (0.25 and 0.50 mL/kg) Ovaprim treatments resulted in better spawning performance. However, superior egg and larval characteristics validate the 0.50 mL/kg dose as the preferred choice for use with pigfish. The four doses of HCG administered to pigfish performed unreliably in this study; thus, no dose recommendation could be made.

Pinfish Lagodon rhomboides and Pigfish Orthopristis chrysoptera are commonly used as marine baitfish in the southeastern United States. Hormone efficacy studies for spawning induction have been conducted with both species, but spawning aids derived from piscine pituitary extracts have yet to be evaluated. Pituitary extract from Channel Catfish Ictalurus punctatus (CCPE) was chosen to determine its efficacy on spawning induction. The CCPE was dissolved in a saline solution and then injected into female broodfish at 5, 10, 20, or 40 mg/kg. The treated females were then paired with conspecific males receiving half the corresponding female dose. Ovaprim served as a positive control at a dose of 0.5 mL/kg for female broodfish and 0.25 mL/kg for males. A single pair of broodfish was randomly stocked according to treatment into separate 1,600‐L tanks within recirculating systems. Broodfish were monitored daily over 72 h after injection for spawning occurrences, and qualitative characteristics including egg and larval morphometrics and viability were quantified. Channel Catfish pituitary extract failed to induce spawning in Pinfish among all dosages administered. All CCPE dosages induced at least one spawn in Pigfish. No significant differences were detected in spawning frequency among treatments although the 10‐ and 20‐mg/kg CCPE dosages and the Ovaprim control each induced ≥50% of Pigfish females to spawn compared with only 16.7% of females treated with the 5‐ and 40‐mg/kg dosages. Floating eggs from Pigfish females in the 10‐mg/kg CCPE treatment were significantly larger than eggs produced using either the 20‐mg/kg CCPE or Ovaprim treatment. Hatching success, larval survival to first feeding, larval length at hatch and first feeding, and oil droplet diameter of recently hatched Pigfish larvae were significantly greater for those larvae from the Ovaprim treatment than for those from the 10‐ and 20‐mg/kg CCPE treatments. Data from these experiments demonstrate the potential use of CCPE to induce spawning in Pigfish, a popular marine baitfish species.