The blood cockle Larkinia grandis is a commercially important resource in the Gulf of California, but little information is available on this species. In this study, the interactions between body weight (BW) and shell length (SL), height (SH), and width (SW) were evaluated in a L. grandis population in the Gulf of California, Mexico. Eighty cockles were hand-picked monthly from August 2017 to July 2018 near and/or under mangrove trees on the southeastern coast of the Gulf of California. The range of shell measurements (SL = 142.00–44.57 mm, SH = 85.50–31.15 mm, SW = 76.56–32.03 mm) indicates that the sampled population was dominated by adult specimens. Only the coefficient of variation for BW exhibited high dispersion (23%–45%). The potential relationships between BW and SL, SH, and SW were non-linear. The strongest interaction was found between BW and SW (R2 = 0.934), with the BW–SW relationship best describing the growth of this ark clam. All shell dimension–weight relationships were significant (P ≤ 0.05), indicating both negative (SL–SW and SH–SW) and positive (SL–SH, BW–SL, BW–SH, and BW–SW) allometric growth. The b values ranged from 0.8950, for the LogSH–LogSW relationship, to 2.6240, for the LogBW–LogSH interaction. This preliminary information is useful for developing conservation and sustainable exploitation strategies for this species, which is of economic importance to this region.

Bivalves reproductive cycle varies according to the particular environmental conditions where they are found, and these reproductive details represent basic information for their capture, management and conservation strategies. With this objective, the reproductive cycle of the clam Megapitaria squalida, inhabiting the Southeast of the Gulf of California (Altata Bay, Sinaloa, Mexico), was studied using histology and changes in the number and size of oocytes, from June 2013 to June 2014. Histological analysis of the gonads showed spawning activity throughout the year, with two peaks. The first was registered in October and it was accompanied by the highest decrease of weight; the second was in February with the highest percentage of spawning population; besides, a resting period was observed in December. The sex-ratio (female:male) of the clam population was 1.08:1 (χ² = 5.72, d.f. = 1, P < 0.05). Mean oocyte size and number were different (P < 0.05) among all sampling months and fluctuated from 34.6 ± 5.8 µm in June 2014, to 41.9 ± 6.8 µm in February 2014, and from 443.8 ± 424.5 in February 2014, to 1 214.4 ± 267.6 counted in April, respectively. With these results we suggest a protection season from October to November, when the most intense release of gametes occur in this population.

The shell height-body weight relationship of the black clam Chionista fluctifraga cultivated in the intertidal of the southeastern Gulf of California, was evaluated for the first time, to improve the knowledge in determining its harvesting time. Clam seeds (n=900,000; 6.1±1.9 mm) were produced in the laboratory. The culture was divided into pre-fattening in racks on the bottom (2 months) and fattening directly in the bottom (16 months) from May 2018 to October 2019. Each month, 60 (n=1080) clams were randomly selected to stablish the morphometric relationship between shell height (SH) and body weight (BW). The growth rate (mm/d and g/d) was recorded. The SH-BW Interaction in both cultivation phases showed positive allometry. SH in prefattening and fattening registered a growth rate of 0.072 and 0.058 mm/d, respectively. In fattening, the interaction BW-SH displayed a high coefficient of determination (R2=0.99). A final survival rate of 90% was obtained. The results yielded the equations that describe the relative growth of C. fluctifraga for the fattening stage. A harvesting time after 10 months of fattening in the intertidal zone is stablished to reach the commercial size (35 mm, SH).

The shape of the shell and the development of bivalve mollusks are strongly associated with the action of environmental conditions. The environmental variables, functional parameters of the shell, and the relative growth of Mytella strigata were seasonally (summer 2020 to spring 2021) determined in three locations: Altata Bay (AB), Macapule Lagoon (ML) and El Colorado Bay (CB) from the southeast Gulf of California (Mexico). Shell dimensions (SL: shell length, SH: shell height, and SW: shell width) showed significant differences. ML mussels obtained the highest measurements (SL = 19.12 ± 1.60 mm, SH = 47.67 ± 3.92 mm, SW = 14.92 ± 1.04 mm, and body weight = 7.54 ± 1.40 g). The greatest shell elongation (SH/SL) was observed in ML (2.49 ± 0.13), while CB recorded the highest compactness and convexity values. SH/SL was the most substantial interaction (R2 = 0.67, 0.63, and 0.55 in AB, ML and CB, respectively). The principal component analysis shows three groupings of the biometric indicators and the relative growth of mussels concerning the environmental parameters in each lagoon. The environmental conditions affected the shape of the shell and relative growth of M. strigata in the three lagoons, emphasizing the type of habitat and salinity as the determining factors. The shell phenotypic plasticity of this mussel represents an adaptive strategy of resilience to the environmental factors in each place.

Objetivo. Determinar la presencia de Perkinsus sp. en la almeja Chionista fluctifraga cultivada en una zona intermareal del sureste del Golfo de California, utilizando la tinción del medio fluido de tioglicolato de Ray (MFTR) y la reacción en cadena de la polimerasa (PCR). Material y métodos. La prevalencia y carga parasitaria de Perkinsus sp. se obtuvieron y se correlacionaron mensualmente con las condiciones ambientales del agua y los indicadores biométricos de la almeja (n=540), de mayo de 2018 a septiembre de 2019. Resultados. Se detectaron presuntas hipnosporas del protozoo en ocho meses de cultivo. La prevalencia fluctuó de 3.3% a 13.3%; la carga parasitaria osciló entre 2 y 1286 hipnosporas/g de tejido. La intensidad de la infección varió de negativa a leve. La prevalencia y la carga parasitaria se correlacionaron positivamente entre sí (r=0.61, P˂0.05), pero no con los parámetros ambientales, ni con los indicadores biométricos de la almeja. La prueba de PCR fue negativa para los casos positivos de MFTR. Conclusiones. Se detectaron presuntas hipnosporas de Perkinsus sp en C. fluctifraga sin claros indicios de infección que comprometieran la salud de la almeja en cultivo. Se recomienda el monitoreo constante de Perkinsus sp. en C. fluctifraga , para establecer posibles infecciones.