Miguel Robles-Mungaray

Phenoloxidase activity in larval and juvenile homogenates and adult plasma and haemocytes of bivalve molluscs.

Phenoloxidase (PO) activity was studied in larval and juvenile homogenates and in the plasma and haemocytes of adult Crassostrea gigas, Argopecten ventricosus, Nodipecten subnodosus, and Atrina maura. Samples were tested for the presence of PO activity by incubation with the substrate L-3, 4-dihydroxyphenylalanine using trypsin, alpha-chymotrypsin, laminarin, lipopolysaccharides (LPS), and sodium dodecyl sulphate (SDS) to elicit activation of prophenoloxidase (proPO) system. PO activity was not detected in larval homogenate. In juvenile homogenate, PO activity was found only in C. gigas and N. subnodosus. PO activity was present in adult samples and was enhanced by elicitors in the plasma of all species tested, but in haemocyte lysate supernatant (HLS) of only N. subnodosus. Activation of proPO by laminarin was suppressed by a protease inhibitor cocktail (P-2714) in plasma and HLS of all species tested.

Ontogenetic variations of hydrolytic enzymes in the Pacific oyster Crassostrea gigas.

Occurrence and level of hydrolytic enzymatic activity (proteases, glycosidases, phosphatases, lipases, and esterases) were studied in oocytes, larvae, juveniles, and adult haemolymph of the Pacific oyster Crassostrea gigas. Samples were obtained as oocyte lysate supernatant, larval homogenate supernatant, juvenile homogenate supernatant, haemocyte lysate supernatant, and plasma. The presence of enzymes was demonstrated by colorimetric and lysoplate assay techniques. Between stages, significant differences in enzymatic activity determined by the colorimetric technique were found. Higher levels of enzymatic activity were found in the adult stage. Lysozyme-like activity was not found in oocytes, but was present in larvae, juveniles, and adults. In larvae, the highest lysozyme-like activity was in 3-d larvae. Juveniles had a 48-fold higher level of lysozyme-like activity, compared with 20-h larvae and was six-fold higher compared with 3-d larvae. In adults, lysozyme-like activity had a five-fold higher level in haemocyte lysate supernatant compared with plasma and was 98-fold higher compared with 20-h larvae. As determined with the API ZYM kit, 19 hydrolytic enzymatic activities were present, in oocytes, larvae, juveniles, and adult haemolymph of C. gigas. The presence of important lysozyme-like activity was confirmed from trochophora larvae (20 h) to adult stages.

Chapter 29 - Scallop Fisheries and Aquaculture in Mexico

This chapter describes the three most important Mexican scallop species (lions paw: Nodipecten subnodosus; Pacific calico scallop: Argopecten ventricosus; Vogdes scallop: Euvola vogdesi), their ecology, fisheries and aquaculture. All commercially important scallops in Mexico occur in the Pacific Northwest and Gulf of California, especially in the lagoon systems along the coast in shallow waters to depths of about 100 m. The three scallop species are fast growing, reproduce early in life, and form large banks that have been commercially exploited over the past decades by hooka-diving from small fibreglass skiffs with outboard engines. As happened in many scallop fisheries around the world, exploitation is characterised by boom and bust phases. Commercial fisheries of Mexican bay scallop started in the early 1980s and represented the most important mollusc fishery in the country from 1985 to 2013, when the banks in Magdalena bay were diminished so much, that the fishery was closed. Vogdes scallop was only locally exploited for a short time, the lions paw, however, has sustained a small commercial fishery in Ojo de liebre and Guerrero Negro lagoons from the early 1990s to 2010 with a maximum production of about 150 mt of meats. In 2010, the population crashed, probably due to a disease, the cause of which is still being investigated. This species was also fished at different sites in the Gulf of California (Loreto, Bahia de Kino), but on a much smaller scale. Today, all scallop fisheries in Mexico are in a serious crisis and are deemed unsustainable. Therefore, large efforts have been undertaken to develop commercial aquaculture of A. ventricosus and N. subnodosus. While hatchery techniques for the former are fully developed and commercial spat production has been accomplished routinely, hatchery production of the latter is still on a small scale, and no commercial spat supply is as yet available, despite a large number of scientific studies on the subject. Small-scale pilot and commercial cultures of both species have been conducted at >15 sites on the Baja California Peninsula and the coasts of Sonora and Sinaloa over the past two decades, with varying results. No active scallop cultures are in operation as of 2015, which shows that they have not been commercially viable for the most part. Lack of spat production, site selection, El Nino years, diseases, handling, market failures, competition with the capture fishery and mismanagement have been quoted as possible reasons, and the Mexican government does not have a comprehensive programme to promote scallop aquaculture. Unfortunately, the large body of scientific studies on scallop aquaculture in Mexico has not translated into an economic alternative for the aquaculture and fishing industry in the region. As fisheries in the region are clearly in decline, efforts should be strengthened to promote sustainable aquaculture of native species and thereby improve the livelihood of coastal communities.

REPRODUCTIVE AND LARVAL PERFORMANCE OF THE PEN SHELL ATRINA MAURA IN RELATION TO THE ORIGIN AND CONDITION OF BROODSTOCK

ABSTRACT The pen shell Atrina maura has economic importance in northwestern Mexico, but limitations to rear larvae in hatcheries increased the interest of scientists and producers to study aspects of reproduction and larval cultivation. Reproductive and larval performances of the species were studied in relation to the origin (depth, phases of tidal cycle) and gross condition of broodstock. The results were correlated to variations in water temperature and concentration of chlorophyll a. Tide influenced spawning response, which was between 40% and 100% successful in broodstock collected during rising and falling tides and only 10% at high or low tides (this percentage corresponds tomales only). The number and size of released and fertilized eggs and the survival of larvae were higher in pen shells collected at 5–8 m depth, compared with those collected at less than 1m. The number and size of released and fertilized eggs, number of veliger larvae, and the survival and growth rate of larvae were significantly higher in January 2012 and correspond to low temperatures, high concentrations of food, high percent of ripe gonads, high-condition index (CI), and low-muscle index (MI). These indicators were significantly lower in March 2012, when broodstock had the lowest percent of ripe gonads, the lowest CI, and the highest MI of all samples. The number and size of released eggs was positively correlated with concentration of chlorophyll a and negatively correlated with temperature, indicating that both factors play a different role in regulating reproductive output.

Settlement and Early Nursery of Juvenile Anadara grandis (Pelecypoda: Arcidae) Under Different Conditions at the Hatchery and Ponds

ABSTRACT Fifteen-day pediveliger larvae of Anadara grandis (shell length, 230 ± 20 µm (mean ± SD, n = 20) were cultivated up to the juvenile stage by testing 2 densities: 71 larvae/cm2 and 283 larvae/cm2 for 37 days. During this time, we registered morphological changes of the larvae from pediveliger up to the juvenile stage, as well as absolute growth, and growth and survival rates. The growth rate was 53.5 µm/day at a density of 71 larvae/cm2, with a survival of 60%; at a density of 283 larvae/cm2, the growth rate was 33.6 µm/day, with a survival of 40%. Subsequently, the juveniles obtained were nursed for 57 days in 2 types of experimental units: Nestier trays suspended in a pond and cylindrical upwelling containers with increasing water flow in the laboratory. In each experimental unit we cultured 66,666 juveniles with a shell length of 1.57 ± 0.05 mm (n = 20). In the Nestier trays, growth was 4–6 µm/day, with a survival of 15%. In the upwelling-type units, growth was 5–6 µm/day, with a survival of 93%. ANOVA revealed significant differences (P < 0.05) in juvenile growth between the Nestier trays and the upwelling-type containers. Low juvenile survival in Nestier trays is attributed to clogging with wind-blown slime. However, a nursery of A. grandis juveniles in ponds requires further research to show its economic feasibility.