Growth of the Pearl Oysters Pinctada mazatlanica and Pteria sterna in Different Culture Structures at La Paz Bay, Baja California Sur, México

A growth study of Pinctada mazatlanica and Pteria sterna was conducted to explain the basic steps required for the development of a pearl culture program in México. Seed for both species was collected using onion bags filled with black polyethylene sheets (40 ± 80 cm) and 5 g of vexar filament. The spatfall was July-August 1987 for P. mazatlanica and December 1987-February 1988 for P. sterna . The seed (12.8 ± 1.2 and 13.0 ± 0.6 mm respectively) was placed in pearl-nets for intermediate culture (to attain 30 mm height). Populations were subsequently divided into three groups, two groups at 10 m depth in lantern and pocket nets and a third placed over a submerged shelf at 10 m depth in plastic net cages. Growth in height, survival and temperature were monitored. After 22 mo P. mazatlanica showed no significant differences in growth between culture structures. Nevertheless, the survival obtained in cages (99%) was larger than that obtained in hanging structures (65%). After 18 mo of culture, significant differences (F = 5.199 P = 0.05) in growth were observed for P. sterna . Larger animals were found in pockets (106.6 ± 0.8 mm) followed by lanterns (104.0 ± 0.7 mm) and finally in cages (103.5 ± 0.6 mm). Survival in pockets was 99%, 84% in lanterns and 98% in cages. With the operation of the different culture structures used in this study, the bottom cage system seems optimal to begin a culture program to obtain pearl-oysters for nucleus implantation.     

In situ growth of pearl oysters Pinctada mazatlanica (Hanley 1856) and Pteria sterna (Gould 1851) under repopulation conditions at Bahia de La Paz, Baja California Sur, Mexico

Pearl oysters Pinctada mazatlanica (Hanley 1856) and Pteria sterna (Gould 1851) were studied for an annual cycle of in situ growth from May 1992 to April 1993. Organisms generated from extensive culture were kept under repopulation conditions at Caleta El Merito. Growth measurements of shell height and length were taken monthly. Data were used to build the annual growth curve of both species, to test the temporal relationship between shell height and length, to calculate monthly and total growth rate, to follow the modal progression with the ELEFAN software, and to fit the growth curve to the Von Bertalanffy equation. Growth dimensions increased steadily during the annual cycle, from 7 to 18 months old for P. mazatlanica and from 11 to 22 months for P. sterna. No significant differences were detected between shell height and length during growth, although length seemed to grow faster. The ELEFAN program identified two modes in P. mazatlanica (Rn= 0.205) and a single one for P. sterna (Rn= 0.557). A positive correlation to the Von Bertalanffy equation was seen for both species (r²= 0.97 for both species).     

Spatfall of pearl oyster, Pteria sterna (Gould), on experimental collectors at Bahía de La Paz, South Baja California, Mexico

Spatfall of pearl oyster, Pteria sterna (Gould), was analysed at two sites, stations Gaviota and Merito, at Bahía de La Paz, South Baja California, Mexico, during an annual cycle in 1991-1992. and from surface to 15 m depth. Sampling was carried out monthly using experimental collectors which remained immersed for 60-65 days. Four different substrates were tested for spat settlement preference: a native bush called ‘chivato’, dry palm leaves, and red and yellow plastic onion bags: temporal variations, and horizontal and vertical spatfall distribution patterns were evaluated between and within stations. Spat settlement showed significant differences depending on the structure and texture of the substrate type. Chivato bush was in general the best spat collector, but was difficult to handle for large-scale operations; plastic onion bags were more suitable and spat yield was adequate; palm leaves were poor spat collectors. There was no evidence for colour preference of spat settlement between red and yellow onion bags. Pteria sterna spat were present throughout almost all of the study period. Main spatfall was detected in winter-spring, coinciding with low temperatures; most spat then occurred from surface to 4-5 m depth. Few spat were present in summer and most then occurred below 7-9 m depth. The distribution patterns of spat within substrate replicates were apparently influenced by the abundance of spatfall. Aggregated spatial patterns were evident in shallow water during months of maximum spatfall but not when spat was less abundant. These events did not occur in the same substrate type, and differences were also detected between stations. Trends were related to oceanographic conditions prevailing at each site. Two patterns of spatfall abundance and vertical distribution were evident, one for winter-spring, and the other for summer. Samples at station Gaviota were grouped by spatfall abundance and spat vertical distribution patterns, while the latter defined better the grouping of samples at station Merito. Geographical variations of spatfall characteristics for Pteria sterna itself, and in comparison with Pinctada mazatlanka (Hanley) in the Gulf of California, are discussed.     

Results of spontaneous spawning of yellow snapper (Lutjanus argentiventris peters, 1869) reared in inland ponds in La Paz, Baja California Sur, México

Maturation and fecundity in two-year cycle of the yellow snapper (Lutjanus argentiventris) was studied as a potential fish-culture species in northwest Mexico. The results of this work will be used in future experiments to control sexual maturation by manipulation of photoperiod and temperature.     

Fouling and predation; how do they affect growth and survival of the blacklip pearl oyster, Pinctada margaritifera, during nursery culture?

This paper reports on 5 experiments conducted to assess the effect of cleaning regime and predation on growth and survival of blacklip pearl oyster (Pinctada margaritifera) juveniles in north Queensland, Australia. P. margaritifera juveniles with a mean (±SE) dorso-ventral shell height (DVH) of 4.5 ± 0.1 mm were placed into plastic mesh trays and cleaned either every 4 or 8 weeks or left uncleaned for 16 weeks. Cleaning regime had a significant effect on growth and survival (P < 0.005). Lowest DVH (16.2 ± 1.0) was shown by oysters in uncleaned trays during 16 weeks compared to oysters in cleaned trays; however, there was no significant difference in DVH between oysters held in trays cleaned every 4 (19.4 ± 1.2) or 8 weeks (21.2 ± 0.8). In contrast lowest survival was shown by oysters held in trays that were cleaned every 4 weeks (30 ± 5%), but no differences were noted between oysters cleaned every 8 weeks (63 ± 4%) and oysters that were left uncleaned for 16 weeks (75 ± 8%). Predators of P. margaritifera in northern Australia included crabs, stomatopods, flatworms, gastropods and fish. The stomatopod, Gonodactylus falcatus, was the most destructive predator with individuals consuming in excess of 20 juvenile pearl oysters per week. The leather jacket, Paramonocanthus japonicus, did not kill pearl oysters, but trimmed the margin of oysters shells significantly reducing DVH when compared to control groups cultured without fish. Removing predators monthly had a significant effect on growth of pearl oysters compared to oysters in non-inspected trays; however monthly inspection of culture trays did not significantly improve oyster survival. This revised version was published online in August 2006 with corrections to the Cover Date.     

Growth and survival of the pearl oyster Pinctada imbricata (Röding 1758) in supended and bottom culture in the Golfo de Cariaco, Venezuela

We evaluated growth and survival rates of Pinctadaimbricata in relation to environmental changes during nine months insuspended and bottom culture in the Golfo de Cariaco, Venezuela. Juveniles,measuring 13 mm in length, were cultured using two methods, (1) inSpanish-type baskets suspended at 3–4 m in depth from a longline and (2) in baskets embedded on the seabed (7–8 m indepth). At monthly intervals, we quantified mortality and took a sample ofoysters to determine shell length (dorsal-ventral axis) and the dry mass of theshell, muscle and remaining tissues. We also quantified the dry mass of foulingon the shells (a potentially important environmental factor). Survival rateswere slightly higher in suspended culture (98–100%), although notsignificantly higher than on the bottom. The growth rate was higher in suspendedculture than on the bottom culture, and the difference between culture methodswas greater for tissue and shell biomass than for shell dimensions. At the endof the study, oysters measured 55 mm in shell length for oysters insuspension and 45 mm for those on the bottom. Although growth wasnot significantly correlated with any environmental factor, it tended toincrease with increases in chlorophyll a during periods ofupwelling, thus suggesting that phytoplankton abundance enhanced the growth ofPinctada imbricata. The pearl oyster Pinctadaimbricata should be an excellent species for aquaculture activities,given its high rates of growth and survival in suspended culture and itseconomic importance in the Caribbean region.