Ricardo Searcy-Bernal

DEVELOPMENT AND CURRENT STATUS OF ABALONE AQUACULTURE IN CHILE

Abstract Abalone aquaculture is rapidly developing in Chile although this mollusc does not occur naturally in this country. The red abalone Haliotis rufescens was introduced in 1977 and the ezo abalone Haliotis discus hannai in 1982. After several years of research and development, the industry began in 1992 and Chile is currently the fifth producer of cultured abalone in the world with 304 tons in 2006. Twenty five companies are involved in this Chilean industry, culturing mainly red abalone. Most of the farms in the North include hatcheries and land-based grow-out operations, whereas most of the in-water grow-out facilities are located in the South. All farms in Chile use algae as the main food for growing abalone, but artificial feeds are also used in some land-based operations in the North. The average size of abalone harvested in Chile is 8 cm (100–120 g) after 3–5 y in culture systems. Whole frozen abalone (shell on) is the most important form of this Chilean product (82% in 2006) and the main market is Japan (90.2%). Abalone production has increased at a rate of around 50% per annum over the last 3 y. This development is expected to continue in the next years, fostered by favorable geographic, economic, and environmental conditions as well as an important government support to invest in abalone. A survey among producers revealed that feed availability and quality is currently considered a key issue to further develop this industry in Chile.

Simultaneous comparison of methods for settlement and metamorphosis induction in the red abalone (Haliotis rufescens)

Abstract This contribution describes two experiments that compare three methods of abalone metamorphosis induction: diatom-film, mucus and gamma-aminobutyric acid (GABA), under commercial-scale conditions. GABA was consistently the most efficient method (72–76% induction after 24 h) while the diatom-film treatment was the least effective (8–12% induction after 24 h). These experiments are the first successful cases of GABA application in the presence of bacteria without using antibiotics. Possible sources of variability in the efficiency of GABA among experiments are discussed.

The effect of irradiance on the survival and growth of abalone postlarvae Haliotis fulgens fed Navicula incerta

Abstract Survival and growth of Haliotis fulgens postlarvae (11 days old) were evaluated at four irradiance levels: 6, 24, 47 and 75 microensteins m−2 s−1 (μE). Experimental vessels were 1-l containers supplied with aeration and seawater flow. Four replicates per treatment were considered. Postlarvae were fed Navicula incerta, a cultured benthic diatom. Survival and growth rates were evaluated for 28 days. Shells were counted to determine mortality and shell size was determined by digital analysis of video recorded images. The highest survival (89.4% after 28 days) and growth rates (37.1 μm day−1) were found at 6 μE, whereas the lowest survival (3.5%) and growth rates (21.1 μm day−1) occurred at 47 μE. These results suggest that light conditions may have a dramatic effect on the success of abalone poslarval culture.

Current Status of Abalone Fisheries and Culture in Mexico

ABSTRACT During the 2008 season, 318 mt (meat weight) of abalone (Haliotis spp.) were commercially fished in México. The species composition of the catch was H. fulgens (70.8%), H. corrugata (28.9%), and H. cracherodii (0.3%). During the past 5 y, total catches increased 29% as a result of the recovery of natural populations of the 2 main species. In particular, H. corrugata catches increased from 50.4 t in 2004 to 91.7 t in 2008 (up by 82%). Currently, 3 private farms culture abalone (mostly H. rufescens) to market size (approximately >7 cm), and 29.6 t of this product were sold in 2008, mostly to markets in Asia and the United States. One of these companies is also producing abalone pearls and jewelry. A new private farm with restocking and growout objectives has just started operations. In addition, 6 hatcheries of fishermen cooperatives produce larvae and seed for restocking purposes and at least 2 of these have started grow-out trials. During the past 2 y, more than 130 million larvae and 350 thousand seeds (approximately > 1.5 cm) of H. fulgens and H. corrugata have been released in the wild stocks by these cooperative hatcheries.

EFFECT OF DARKNESS AND WATER FLOW RATE ON SURVIVAL, GRAZING AND GROWTH RATES OF ABALONE HALIOTIS RUFESCENS POSTLARVAE

Abstract The effect of two light conditions (light at 10–13-μmol quanta/m2/s and darkness) in three water flow rates (0, 200, and 600 mL/min) on the survival, grazing, and growth rates of 6-day-old Haliotis rufescens postlarvae (pl) was evaluated. A factorial experiment with three replicates per treatment in blocks was conducted for 44 days in 2-L plastic containers with ca. 100 postlarvae each, inoculated every week with the cultured diatom Navicula incerta. Survival was highest (80%) in the treatment without water flow and with light, whereas the lowest (52%) corresponded to the 600-mL/min flow rate under darkness, but these differences were not significant. Initial grazing rate was significantly higher in darkness than in light (37 cell/pl/hr, SE = 1.6, and 27 cell/pl/hr, SE = 2.8, respectively). Growth rate was not significantly affected by the light treatments. However, in static conditions growth was higher in darkness (38-μm/day, SE = 2.0) than in light (34-μm/day, SE = 1.0). Growth rates of postlarvae were significantly affected by flow conditions, with means of 36 (SE = 1.3), 33 (SE = 0.7) and 31 (SE = 0.7) μm/day in flows of 0, 200, and 600 mL/min, respectively). These results suggest that the benefits of dark conditions on the growth rate of abalone postlarvae shown in previous experiments might not occur under flow conditions. However, the flow rates tested here were apparently too high to allow an optimal postlarval growth and slower flows should be tested in future experiments. On the other hand, flow allowed the development of high diatom densities under the light condition, which were difficult to maintain in darkness.

EFFECTS OF ANTIBIOTICS ON THE CONCENTRATION OF BACTERIA IN BIOFILMS AND ON THE GROWTH OF HALIOTIS RUFESCENS POSTLARVAE

Abstract The effects of chloramphenicol and streptomycin/penicillin on the concentration of heterotrophic bacteria in biofilms associated with abalone postlarval culture and on the growth and survival of Haliotis rufescens postlarvae (3–5 days old) were studied under laboratory conditions. Two experiments were carried out in 12-well polystyrene tissue culture plates with 5 mL of 1-μm-filtered autoclaved seawater. Water was changed every other day and antibiotics were added during the water change. Experimental units were previously inoculated with the benthic diatom Navicula incerta. In the first experiment chloramphenicol at 0, 5, 10, and 20 mg L−1 was used and a mixture of streptomycin and penicillin at 0/0, 50/50, 100/100, and 150/150 mg L−1 was tested in the second experiment (in both cases with three replicates). Bacterial counts (Zobell plates) were performed for a period of 4 and 5 wk (experiments 1 and 2, respectively). Bacterial densities decreased 90% in 20 mg L−1 of chloramphenicol during the first 48 h; however, bacterial counts increased in all treatments thereafter and differences were not significant at the end of the experiment. The growth of abalone postlarvae was not significantly different among treatments. In the experiment with antibiotic mixtures, bacterial abundance was reduced 99% at the highest concentration (150/150) in the first 48 h, and remained significantly lower than the control for 2–3 wk. During this period, postlarval growth in this antibiotic treatment was also slower, as well as final survival, suggesting an important role of bacteria in the nutrition and/or digestion of abalone postlarvae. Results of this study also suggest that bacterial resistance to these antibiotics develops fast, discouraging their long-term use in abalone culture.

METAMORPHOSIS AND POSTLARVAL GROWTH OF ABALONE HALIOTIS RUFESCENS IN A MEXICAN COMMERCIAL HATCHERY

Abstract Metamorphosis induction and postlarval growth of the red abalone (Haliotis rufescens) were evaluated in a commercial farm of Baja California, México. This hatchery settles larvae with gamma-aminobutyric acid (GABA, 1-μM final concentration) and culture postlarvae in 250-L tanks placed in a four-story structure inside a building with artificial illumination. Eight tanks (four at the top and four at the bottom of a culture structure) were sampled during four months after settlement. Upper tanks received more light than the lower tanks (means of 727 and 217 lux, respectively) and had a higher mean water temperature (14.9°C and 14.4°C, respectively). Estimates of metamorphosis induction were highly variable (37% to 99%) and mean values were higher in lower (76%) than in higher (54%) tanks. Potential causes of this unexpected variability are discussed. There was a significant positive linear relationship between metamorphosis induction and early (7-day) postlarval survival. Average postlarval growth rates were also highly variable among tanks (37–63 μm/day) and slightly higher in upper than in lower tanks (60 and 52 μm/day, respectively). During the sampling period, growth variability was positively associated with water temperature changes, especially after the formation of the first respiratory pore when growth increased abruptly.

Restocking of Abalone Populations (Haliotis spp.) in Mexico

ABSTRACT Abalone restocking in the peninsula of Baja California, Mexico, has been practiced for more than 2 decades by fishermen cooperatives. We describe the methods used to produce and release abalone larvae and seeds by these organizations, and provide their recent production statistics. From 2005 to 2011, 2.2 million seeds (>15 mm) and 692 million competent larvae were produced by 6 cooperative hatcheries and released in their fishing grounds. Of these, 90.1% of the seeds and 80.7% of the larvae corresponded to Haliotis fulgens, whereas the figures for Haliotis corrugata were 9.9% and 19.3%, respectively. The research conducted in Mexico on the evaluation of the impact of restocking is also addressed. Preliminary results suggest that less than 5% of the seeds stocked are incorporated into commercial catches.

EFFECT OF TWO STOCKING DENSITIES ON THE GROWTH AND MORTALITY OF THE PINK ABALONE HALIOTIS CORRUGATA IN RECIRCULATING AND FLOW-THROUGH SYSTEMS

Abstract Traditional abalone culture is carried out in flow-through systems with water exchange rates between 200 and 2,400% of the total tank volume per day. These high volumes of water associated with abalone culture represents a constraint for the growth of this industry, and recirculating systems can become a viable alternative, because the water exchange rates are less than 10% of the total volume. The objective of this experiment was to evaluate the water quality parameters and the growth rate and mortality of the pink abalone cultured at two different densities, 10% (D1) and 30% (D2) in a flow-through system (S1) and two closed recirculating systems (S2 and S3). A total of 2,400 juvenile abalone (7.11 ± 2.0 g and 37.01 ± 3.4 mm) were distributed among the three experimental systems. The experiment lasted for 127 days. Weight and length of all the abalone were measured at the beginning and end of the experiment. Average water quality parameters for each system (S1, S2, and S3) were respectively: temperature (18.2 ± 1.4, 18.4 ± 1.9, and 18.1 ± 2.0°C); salinity (33.8 ± 1.0, 34.5 ± 1.2, and 34.2 ± 1.5‰); alkalinity (127 ± 13.2, 135 ± 13.7 and 131 ± 14.1 mg of CaCO3/L), total ammonia nitrogen (0.006 ± 0.02, 0.03 ± 0.07, and 0.02 ± 0.08 mg TAN/L) and nitrite (0 ± 0.00, 0.08 ± 0.07, and 0.07 ± 0.05 mg NO2/L). Growth rates in weight (g/d) were for S1D1 (0.027 ± 0.007), S1D2 (0.018 ± 0.001), S2D1 (0.007 ± 0.001), S2D3 (0.005 ± 0.000), S3D1 (0.007 ± 0.000) and S3S2 (0.009 ± 0.003), and growth rates in length (mm/d) were for S1D1 (0.038 ± 0.004), S1D2 (0.031 ± 0.002), S2D1 (0.013 ± 0.001), S2D3 (0.013 ± 0.000), S3D1 (0.002 ± 0.000), and S3D2 (0.024 ± 0.001) respectively. In flow through systems growth in length and width was density dependent. Mortality was higher in S3D2 than in any other treatment. A lower water exchange rate in closed systems could adversely affect growth and mortality. Abalone culture in closed recirculating systems could become another alternative for this industry, but more research is required.

Survival and Growth of Red Abalone (Haliotis rufescens) Postlarvae Under Different Static and Flow Conditions

ABSTRACT The effect of different strategies of opening water flow on the survival and growth of Haliotis rufescens 9-d postlarvae was evaluated using a randomized block design with 3 replicates for 63 days. Larvae were settled (1.5 µM gamma-aminobutyric acid) in 2-L plastic vessels (total area, 701 cm2) and were subjected to the following treatments: static conditions, static conditions with aeration (NF + A), flow opened after 10 d, flow opened after 17 d, and flow opened after 24 d. The experiment was conducted at constant temperature (17.5 ± 0.5°C) and light intensity (∼750 lux). Water was changed daily in static treatments, and flow treatments received filtered seawater at ∼60 mL/min. Postlarvae were fed the benthic diatom Navicula incerta per standardized protocols. Every week, all organisms in each experimental unit were counted to estimate survival, and samples of 15 postlarvae were recorded under an inverted microscope and measured using digital image analysis. At the end of the experiment, greater survival occurred in treatment NF + A (68.2%) and was the lowest in the treatment in which flow was opened after 10 days (26.9%); however, no significant differences were found (P > 0.37). The greatest growth rate was observed in the treatment in which flow was opened after 24 days (61.6 µm/d), and the lowest was seen in static conditions (47.6 µm/d and 44.6 µm/d for static conditions and NF + A treatments, respectively). An inverse relationship between final growth rates and postlarval densities was found. Our results suggest that abalone postlarvae can be cultured successfully in static conditions with aeration, but feeding routines should be improved to allow high growth rates at high stocking densities.