ALBERT

Notes: Implanted pellets that provide a sustained release of [D-Ala6 Des-Gly10] LHRH-ethylamide (GnRHa) were used to induce maturation and ovulation of Southern flounder Paralichthys lethostigma. Of the 12 females whose ovaries contained follicles with a maximum diameter ≥500 μm, 11 ovulated for the first time within 90 h of hormone implantation. Only 1 fish with a maximum follicle diameter less than 500 μm ovulated within 2 wk after implantation. Ovulated eggs were manually stripped from the females and mixed with sperm from several males. Most females were spawned 1 to 3 times on consecutive days with variable fertility. One female was spawned 11 times producing 668,000 eggs. Fertility was evaluated by examining the incubated eggs for early stages of embryonic cleavage. The percentage of fertile eggs in subsamples of incubated eggs ranged from 7–95%. The results indicate that GnRHa implants can be used to induce repeated ovulation in this species. The variability in fertility is discussed in relation to egg quality.

Notes: The gametogenic cycle of the white bass Moronc chrysops was characterized for one year at monthly intervals by measuring circulating levels of the sex steroid hormones testosterone (T) and 11-ketotestosterone (11-KT) in males, and 17β-estradiol (E2) and T in females. Vitellogenin (VTG), the egg yolk precursor, was also measured in female blood plasma. Gonadal status of individual fish was assessed by histological evaluation, measurement of oocyte diameters, and spermintion response. At the onset of vitellogenesis (October), blood plasma levels of E2 and T were low, but increased significantly as the spawning period (March-April) approached and oocytes attnined their maximum diameter. All stages of oocyte development were observed in mature females, indicating that the white bass is a multiple-clutch, groupsynchronous spawner. Androgen levels increased in males throughout the reproductive cycle and reached maximal levels during the spawning period. The increase in androgens coincided with sperm production and spermintion in males. The circannual endocrine and gonadal development patterns observed in white bass were similar to those of other members of genus Moronc.

Notes: The effects of extender composition, cryoprotectant, and freezing rate on post-thaw rainbow smelt Osmerus mordax sperm motility were examined, and the fertilization capacity of fresh and post-thaw sperm were compared. The highest post-thaw motility (75%) was obtained when milt was diluted 1:3 with an extender containing 600 mM sucrose supplemented with 10% dimethyl sulfoxide and 1.5% bovine serum albumin and frozen at a rate of –20 C/min. Post-thaw motility for sperm stored in this extender was similar to fresh sperm and did not change after 90 d of storage. Furthermore, there were no differences in fertilization rate or embryo survival to the eyed stage between fresh and post-thaw sperm frozen in this extender. The lowest post-thaw motility was observed when sperm were frozen with methanol at a rate of -30 C/min. Refrigerated sperm diluted 1:3 with the 600 mM sucrose extender remained motile for 30 d. These data demonstrate that rainbow smelt spermatozoa can be effectively used following short and long-term storage using a simple, sucrose-based extender.

Notes: During their first year in captivity, summer flounder Paralicthys denratus were induced to spawn with gonadotropin releasing hormone analogue (GnRHa) implants, injected carp pituitary extract (CPE) or human chorionic gonadotropin (hCG) injections. The percentage of fertile eggs was greatest (69%) in CPE-treated females. CPE, but not GnRHa or hCG, was capable of stimulating oocyte growth (increased follicle diameter during vitellogenesis) followed by ovulation. Fish with maximum ovarian follicle diameters between 180 and 435 μm at the initiation of CPE injections produced the greatest percentage of fertile eggs. For most females, fertilization rate was greatest for the first batch of eggs ovulated. The mean fertilization rate for the first spawn of CPE-treated fish was 42% compared with 14% for the second spawn from the same fish. Fish with maximum initial follicle diameters of 585 40 μm that were implanted with GnRHa ovulated the greatest number of eggs, but fertility was low and variable. Approximately 35% of females injected with hCG ovulated a limited number of eggs, but only one hCG-treated female produced fertile eggs. Only a limited number of spermiating males were available for spawning trials. Hormone treatments used on females were ineffective for inducing or maintaining spermiation in male summer flounder.

Notes: Along the Atlantic coast black sea bass occur from the Gulf of Maine to Florida and support important commercial and recreational fisheries. Interest in commercial production of black sea bass has increased in recent years due to high demand and limited seasonable availability. Efforts towards large-scale production have been hampered by a high incidence of early larval mortality. Two of the most important environmental variables affecting hatchery production of marine finfish larvae are temperature and salinity. In the wild, larval black sea bass are found in waters with temperatures of 12–24 C and salinity levels of 30–35 ppt. Studies were conducted to define the temperature and salinity ranges that support growth and development of black sea bass during early life stages. Three developmental phases were investigated: 1) fertilization to hatch: 2) hatch through yolk sac absorption: and 3) during the initial exogenous feeding stage (5–14 days post hatch: DPH). Fertilized eggs were obtained by manual spawning of fish following administration of LHRHa. Fertilized eggs were transferred to 300-mL glass Petri dishes or 500-mL beakers to assess the effects of salinity and temperature through hatch and yolk sac absorption, respectively. To determine environmental effects on growth and survival during initial exogenous feeding 400 actively feeding larvae were cultured in green water and fed enriched rotifers for a 9-d period. For investigation of the effect of salinity, sea water (35 ppt) was diluted gradually to 15, 20, 25, and 30 ppt and maintained at 21 C. For examination of the effect of temperature, seawater was adjusted from 21 C to 12, 15, 21, 27, or 30 C at a rate of 3 C/h. No eggs hatched at 12 C or when salinity was maintained at 0 or 5 ppt. Hatching was uniformly high (≥ 85%) at temperatures between 15 and 27 C and at salinities ≥ 15 ppt. Survival through yolk sac absorption was greatest at temperatures between 18 and 27 C and at salinities ≥ 20 ppt. Survival through first feeding stage was highest at temperatures ≥ 18 C and 30 ppt salinity. Larval growth through first feeding was not significantly affected by salinity level but did increase with rearing temperature. The results indicate that survival and development of black sea bass during early life stages are most favorable at temperatures 〉18 C with salinity levels approaching full strength seawater.

Notes: The black sea bass is a high-value marine serranid and is a prime candidate for intensive cultivation. Reliable methods for controlled spawning are needed to accelerate the development of hatchery technologies that result in mass production of healthy juveniles. During 1998–2001, spawning studies were conducted at The University of North Carolina at Wilmington (UNCW) and at the South Carolina Department of Natural Resources (SCDNR), Charleston, using pelleted luteinizing hormone releasing hormone analogue (LHRH-a).From April through July 2001, 28 vitellogenic-stage females, with mean oocyte diameters (MOD) ranging from 277–448 μm, were implanted with a 95% cholesterol-5% cellulose pellet containing LHRH-a (-50 μg/kg body wt) at UNCW. In 10 individual spawning trials, females with MOD of 305–448 μm and maximum oocyte diameter × 475 μm spawned volitionally beginning 2–3 d post-implantation (PI) and continued spawning over an average of 1.9 d (range = 1–4 d). Individual females released a mean total of 149,000 eggs (117,000 eggs/kg) with a mean buoyancy rate of 40.5% (floaters). Fertilization and hatching rates were 98% and 27.2% of floaters, respectively, yielding 14,600 yolksac larvae/female (12,600 yolksac larvae/kg body wt), and overall egg viability averaged 8.9%. In eight group spawning trials (2–3 females/group), average performance of females, including fecundity (103,800 eggs/female; 105,500 eggs/kg body wt), buoyancy rate (42.5%), fertilization and hatching rates (97.7% and 24.3% of floaters), numbers of yolksac larvae produced (10,900 yolksac larvae/female; 10,100 yolksac larvae/kg body wt), and overall egg viability (10.6%) was comparable to what was seen in individual spawning trials.From 1998–2000, a total of 58 vitellogenic stage (70% of oocytes 500 pm) females were implanted with pelleted LHRH-a (-50 μg/kg body wt) in nine group spawning trials (2–19 females/group) at SCDNR. Volitional spawning typically began 18–42 h PI and recurred every 1–3 d for an average duration of 9 d. Female groups released a mean of 560,000 eggs (84,000/female; 132,000/kg body wt) over the spawning period, with mean buoyancy rate of 25.7% floaters. Fertilization and hatching rates were 17.7% and 11.6 % of floaters, respectively, yielding 4,300 yolksac larvae/female (4,600 yolksac larvae/kg body wt). Overall egg viability was 2.9%.Captive wild-caught black sea bass were induced to undergo repetitive volitional spawning by implantation of pelleted-LHRH-a, consistent with a multiple clutch group synchronous pattern of ovarian development. Group spawning appears to be a practical way to compensate for variable fecundity and egg viability of individual females. Research is needed to identify optimum hormone treatments and eligibility requirements.

Notes: Juvenile and adult black sea bass (Centropristis striata L.) were exposed to various concentrations of four anaesthetics to determine practical dosages for handling as well as for procedures such as bleeding, ovarian biopsy or tag implantation. In experiment 1, juveniles exposed to either 2.0 mg L−1 metomidate, 15 mg L−1 clove oil, 70 mg L−1 tricaine methanesulphonate (TMS) or 200 mg L−1 2-phenoxyethanol (2-PE) reached stage II of anaesthesia in 3–5 min and could be handled for weighing and measuring. All fish had completed recovery to stage III within 6 min. In experiment 2, the established concentrations of each anaesthetic were tested on juveniles to determine their ability to prevent a reflex to a subcutaneous needle puncture. All of the fish exposed to clove oil (20 mg L−1) and 40% of the TMS-treated (70 mg L−1) fish reacted while none of the fish anaesthetized in metomidate (2.0 mg L−1) or 2-PE (200 mg L−1) responded to the needle puncture. In experiment 3, metomidate (5.0 mg L−1), clove oil (30 mg L−1) TMS (125 mg L−1) or 2-PE (300 mg L−1) were all effective for performing an ovarian biopsy or tag implantation on adults. In experiment 4, TMS (125 mg L−1) exacerbated the cortisol response to a short handling stressor during a 30 min exposure. Fish anaesthetized in 2-PE (300 mg L−1), metomidate (5.0 mg L−1) or clove oil (40 mg L−1) had increased cortisol levels associated with the handling stressor but there were no further increases during the remainder of the experimental period. The results demonstrate that these anaesthetics are effective for sedation and anaesthesia of black sea bass and that the best choice is dependant upon the procedures to be performed.

Notes: Four experiments were conducted to investigate the effects of feeding frequency on growth of juvenile Atlantic halibut, Hippoglossus hippoglossus L. Fish (22–75 g) fed three (3 ×) or five times per day (5 × day−1) under constant light and temperature (13±1°C) consumed significantly more feed than fish fed 1 × day−1 but by the end of the experiment only fish fed 5 × day−1 were heavier and had greater specific growth rates (SGR). Under simulated winter conditions (9L:15D, 5±1°C), halibut (∼300 g) fed every other day consumed more feed, had a greater SGR and final weight compared with fish fed every third day. Feed conversion ratios were not different among treatment groups in any of the experiments. These results suggest that growth rates may be improved by feeding juvenile halibut more than 1 × day−1.

Notes: Haddock (Melanogrammus aeglefinus L.) were maintained on either simulated natural (SNP) or advanced, phase-shifted photoperiods (ADV) and reproductive characteristics of female fish were measured throughout two reproductive cycles. By advancing the seasonal photoperiod 8 weeks, relative to ambient conditions, follicle development, peak levels of estradiol and initiation of spawning were all accelerated compared with fish maintained on an SNP. Profiles of steroid synthesis and follicular development were similar between the two groups but the spawning period was protracted by 40 days in the fish maintained on ADV. Ultrasound imaging proved to be an effective and non-invasive tool for accurately assessing ovarian development throughout the reproductive cycle. These results suggest that photoperiod manipulation has significant potential for extending the availability of eggs and larvae for haddock aquaculture.