Volitional Spawning of Black Sea Bass Centropristis striata Induced with Pelleted Luteinizing Hormone Releasing Hormone-Analogue

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.     

Growth and Feed Utilization of Captive Wild Subadult Black Sea Bass Centropristis striata Fed Practical Diets in a Recirculating System

The effects of four practical diets on growth, feed utilization, and body composition of wild‐caught juvenile and subadult black sea bass Centropristis striata (316 ± 113 g =±± SD) were compared for 221 d in a recirculating tank system consisting of 12 2,660‐L tanks. Salinity averaged 33.5 ppt and temperature averaged 20.9 C but vaned from 12 to 27.1 C. Diets differed in crude protein (CP) and crude lipid (CL) as follows: 1) low CP (44.0%), low CL (11.4%) trout diet; 2) low CP (44.8%), high CL (15.0%) trout diet; 3) midlevel CP (47.9%), midlevel CL (12.8%) Bounder diet; and 4) high CP (53.9%), high CL (15.1%) marine finfish diet. Energy: protein ratios (E: P) were 44.6, 45.3, 41.8, and 39.1 W/g. Survival to 221 d on all diets was 100%. Significant (P < 0.05) differences in growth rates were observed among diets. Final weights were higher for midlevel and high CP diets 3 and 4 (1,051 and 1,013 g) than for low CP diet 1 (873 g). Relative growth rate (RGR, % total increase in weight), specific growth rate (SGR, % increase in body weight/d), and daily weight gain (DWG, g/d) were higher for higher CP diets 3 and 4 (RGR = 223 and 221; SGR = 0.53; DWG = 3.28 and 3.16), than for low CP diet 1 (RGR = 181; SGR = 0.47; DWG = 2.54). There were no significant differences between initial and final whole body protein and fiber content among diets. Lipid and gross energy levels significantly increased (P < 0.0001) in all treatments while moisture levels significantly decreased (P < 0.001). Although these differences were not significant, feed conversion ratio (FCR = dry weight fed/wet weight gain) was lower for fish given midlevel CP diet 3 (1.49) and high CP diet 4 (1.52) than for those fed low CP diets 1 and 2 (1.60 and 1.62). Protein efficiency ratios (PER = weight gain/weight protein fed) (1.43 to 1.24), apparent net protein retention (ANPR = weight protein gain/weight protein fed) (20 to 25%), and apparent net energy retention (ANER = energy gain/energy fed) (53.3 to 56.8%) were not significantly different among treatments. The midlevel CP (50%), midlevel CL (12%) diet maximized growth rates and was also significantly less expensive per kg fish weight produced ($1.40) than the high CP diet ($1.94) which produced the second highest growth rates. These results demonstrated that wild‐caught black sea bass can be successfully reared in recirculating tanks from juvenile to marketable sizes with high survival and with good feed conversion and growth on commercially prepared diets with a wide range of protein and lipid levels.     

Residency and movement of stream-dwelling Japanese charr, Salvelinus leucomaenis, in a central Japanese mountain stream

Abstract – The residency and movement of stream-dwelling adult (2+ and older) Japanese charr, Salvelinus leucomaenis , were studied by mark and recapture experiments in the Jadani Stream, a headwater tributary of the Tedori River, central Japan, from 1986 to 1989. Of the marked fish, 31.3–58.3% were recaptured in the same pools where they had been caught during the study periods of summer (June–August), autumn (August–November) and winter–spring (November to the next June) and no seasonal movement was observed. The mean distances that the fish moved during the study periods ranged from 139.0 to 502.3 m and many movements longer than 1000 m were observed. Between the resident and the moved fish, there was little difference in body length, growth rate or sex. For the fish that had been resident in the same pools and riffles at previous recaptures, most fish were recaptures in the same locations at the next recapture. Conversely, for the fish that moved previously, most fish were recaptured in different locations from previous sites at the next recapture. These results suggest that Japanese charr exhibit relatively high residency throughout the year, but many fish moved longer distance. The results also suggest the presence of static and mobile components in the charr population.     

Economic Evaluation of Commercial-Scale, Saltwater Pond Production of Florida Red Tilapia in Puerto Rico

An economic analysis was performed of a proposed commercial-scale 20-ha saltwater pond culture operation for Florida red tilapia in Dorado, northern Puerto Rico. The analysis was based on actual cost and production data from a commercial-scale hatchery, pilot-scale grow-out trials conducted in six 0.2-ha saltwater (avg. = 22.7 ppt) ponds at the Dorado facility and on wholesale market prices ($4.96–5.18/kg) fetched by dressed-out (gilled, gutted and scaled) product. The proposed 20-ha growout facility is comprised of 25 0.8-ha earthen ponds, each supplied with sea water, brackish well water, drainage and aeration, which account for 60.8% of the capital costs. Ponds are stocked with fingerlings (0.85 g avg. wt.) at a density of 3.0 fish/m² (30,000/ha), and are harvested at 160 and 220 d, at an average weight of 545 g for a total yield of 11,445 kg/ha per crop. Imported feed ($0.55/kg), processing and distribution ($0.50/kg) and sex-reversed fry ($0.11/fry) are the highest variable costs, accounting for 30.7%, 15.4% and 13.9%, respectively, of the total annual costs. Salaries and benefits, and depreciation represent the highest fixed costs, accounting for 8.4% and 5.5%, respectively, of the total annual costs. Under these conditions, a wholesale price of $4.55/kg results in a positive cash flow by year eight, and a breakeven price, internal rate of return (IRR), net present value (NPV) and discounted payback period (DPP) of $4.08/kg, 7.6%, ($235,717) and >10 yr, respectively, suggesting that the proposed 20-ha operation is not economically feasible under these conditions. The proposed enterprise is marginally feasible if stocking density is increased to 3.5 fish/m² while at 4.0 fish/m² economic outlook is favorable. Costs can be lowered considerably by targeting production and market variables most sensitive to profitability indices, using locally-prepared feeds, and vertically integrating hatchery and growout operations.     

Artificial Propagation of Mutton Snapper Lutjanus analis, A New Candidate Marine Fish Species for Aquaculture

Abstract Wild-caught mutton snapper Lutjanus analis , a high-value marine food fish species, matured in flow-through seawater (36 g/L) tanks after 3 yr in captivity. On 31 May 1995, a female with a mean oocyte diameter of 382 μm was injected with human chorionic gonadotropin (HCG) (500 IU/kg body wt.) followed 24 h later by a second injection (1,000 IU/kg body wt.). At the time of the second injection, three males were injected with HCG (500 IU/ kg body wt.). Voluntary spawning occurred 33 h after the first injection, with a total of 534, 781 eggs released. Fertilization rate was 75.7%, while average diameter of fertilized eggs was 783 μm. Embryos were stocked in a 30-m³ outdoor tank at a density of 10.5/L. On day 2 post-hatching (d2ph), larval density was 8.61 larvae/L, and average notochord length was 2.6 mm. Larvae were fed ss-type rotifers from dl-d28ph, Artemia nauplii from 0–08ph, and artificial diets (52–48% protein) from d24-d38ph. On d38ph, fish averaged 0.308 g and 22.2 mm standard length. Survival (from d2ph) was 14.3%, with a total of 36,900 post-metamorphic juveniles produced. On d97ph, 1,390 hatchery-reared juveniles (avg. wt. = 10.5 g) were stocked into two 14.5-m³ recirculating seawater tanks (695 fish/tank; 48 fish/m³) and fed a 56% protein pellet. After 168 d, fish averaged 140.8 g, with a survival rate of 97.8% and a feed conversion ratio (dry wt./wet wt.) of 1.2. These preliminary results reveal the mutton snapper to be a prime, new candidate species for commercial cultivation.     

Breaking the crossability barriers between disomic tetraploid Solanum acaule and tetrasomic tetraploid S. tuberosum

Summary A combination of compatible second pollinations and embryo rescue was applied for systematic production of true tetraploid hybrids from crosses between disomic tetraploid Solanum acaule and tetrasomic tetraploid potato, S. tuberosum. Several genotypes of tetraploid potatoes were pollinated with S. acaule, and the compatible second pollinations were made on the following day, with a genotype of S. phureja, IvP 35 to promote fruit development. Embryo rescue was carried out in 21 families, 14 to 27 days after the first pollination. A total of eight plants were obtained from the embryo rescue and their chromosome numbers were counted in the root tips. Three of the eight plants were identified as tetraploid, and five others as diploid. Morphology, isozyme banding patterns, and pollen stainability, as well as potato spindle tuber viroid (PSTVd) resistance, indicated the hybrid nature of the three plants. This is the first report of successful tetraploid hybrid production between disomic tetraploid S. acaule (4x) and tetrasomic tetraploid potatoes. Seed set from the crosses between one of hybrids and diploid potatoes indicated workable levels of both male and female fertility for introgression of valuable genes from S. acaule into the cultivated potato gene pool. The methodology used may be applied to other disomic tetraploid tuber-bearing Solanum species and with some modifications also to distantly related solanaceous species and genera.     

Near-isogenic lines of durum wheat: their development and plant characteristics

Summary The effect of specific plant characteristics on the grain and biomass yield of durum wheat can be accurately determined by using isogenic lines, which, however, were not usually available. This study reported the effects of long glume, glaucousness, glume pubescence, black glume and purple culm on the yield and its associated characteristics in near-isogenic lines of durum wheat cv. LD222, which were developed by continuous backcrossing. The long glume trait which resulted in a large photosynthetic area did not enhance yield. Increased glume size associated with the P gene tended to increase the main culm dominance, characterized such as vigorous main culm and weak tillers, and plant height, but to reduce tillering and spike number. Consequently, grain yield and harvest index declined. Under the adequate water supplying condition of the present study, the glaucous trait was beneficial for grain yield. The trait of glume pubescence did not excert any significant effect on the yield related characteristics in the LD222 background. The traits of black glume and purple culm reduced the number of spikes per unit area and the number of kernels per unit area.     

Construction and characterization of a BAC library of soybean

We have constructed a soybean (Glycine max (L.) Merrill) bacterial artificial chromosome (BAC) library from green leaf protoplasts of the cultivar, Misuzudaizu. The library contains 53,760 clones with an average insert size of 116 kb. About 2.9% chloroplast DNA origin was revealed by PCR and colony hybridization. Apart from 2.8% clones having no insert, this library represents 5.2 genome equivalents. With this genome coverage, the probability of having any DNA sequence represented in the library is higher than 99.5%. Three-dimensional pools of the BAC library in combination with the use of a high efficiency genome scanning (HEGS) electrophoresis facilitate rapid and efficient PCR-based screening. An average of five positive clones were identified after screening the BAC library with SSR and STS markers. BAC-end walking was performed for three SSR associated BACs. This library will provide a good resource for positional cloning of agronomically and biologically important QTL genes that Misuzudaizu possesses.