R/AQ-4

Description:

OBJECTIVES: To develop Greater Amberjack, Seriola dumerili, as a new US aquaculture species, research efforts are needed to improve the juvenile supply in captivity. The overall goal is to describe the reproductive cycle and its endocrine dysfunction, from pre-puberty through early gametogenesis and spawning of females held in controlled thermo-photoperiod conditions in a biosecure recirculating aquaculture system. This goal will be achieved through 3 key objectives: Objective 1: Study puberty and the reproductive cycle of S. dumerili held in captivity. Objective 2: Develop a GnRH-based technology to induce captive spawning. Objective 3: Study the effect of different environmental regimens on phase-shifting the spawning time. The information derived from these objectives will be used in the subsequent reproductive manipulation of adult S. dumerili females to produce fertilized eggs and viable larvae on demand, thereby spurring regional economic development through safe and sustainable aquaculture practices. METHODOLOGY: Using an optimized GnRHa-based technology, a predictable and on-demand spawning technology for captive Seriola dumerili will be developed. A detailed description of the neuroendocrine profiles of neurohormones along the hypothalamus-pituitary-gonadal axis during female puberty and gonadal development will be generated to detect the stages of hormonal failure. On that basis, we will formulate suitable GnRHa delivery devices to promote ovarian development and/or ovulation and spawning. Two delivery systems will be tested in females arrested at early and late vitellogenesis to address these two potential blockages during ovarian development: 1) A slow and prolonged delivery system composed of FAD-SA microspheres, and 2) an EVAc-based delivery device that releases the hormone faster. We then will evaluate the efficiency of the devices by monitoring spawning, egg quality and fry viability. Further, by exposing broodstock to environmental manipulation, a permanent phase-shifting of gonadal development will be established that enables year-round spermiation, ovulation, spawning. RATIONALE: The proposed work is specifically designed to solve a bottleneck that currently hampers development of a US industry for S. dumerili, as well as the Seriola industry worldwide. Despite its ready adaptation to captivity, S. dumerili puberty, reproductive maturation and spawning has proven very unreliable. The basis of the proposed study is the understanding that a hormonal failure in captivity, which has been shown in many culture species, leads to oocytes arrested in vitellogenic stages and is ultimately the main reason for the lack of spawning of fish in aquaculture. GnRH-based spawning induction therapies, developed and widely implemented by the PI's laboratory, have solved this problem in a number of commercially important marine finfish. The availability of technologies to monitor important reproductive hormone, as available in the Zohar laboratory, provide the basis for tailoring the optimal dose and pattern of GnRHa required to induce good quality eggs and juveniles.