Eugenio Alberto Aragón-Noriega

MORPHOMETRIC RELATIONSHIPS, GAMETOGENIC DEVELOPMENT AND SPAWNING OF THE GEODUCK CLAM PANOPEA GLOBOSA (BIVALVIA: HIATELLIDAE) IN THE CENTRAL GULF OF CALIFORNIA

Abstract This paper describes morphometric relationships, and the timing of gametogenic development and spawning for the geoduck clam Panopea globosa (Dall 1898) from a population in the east central Gulf of California. Clams were collected monthly for a year (October 2004 to October 2005), and were measured and weighed to obtain morphometric relationships. Standard histological analysis and measurements of oocyte diameters were used to describe the timing of gametogenic development and spawning. Most morphometric variables were significantly correlated, however the coefficients of determination were generally low (<0.5) indicating high variation in measured traits. Early gametogenic development was observed in late summer/autumn when SST was high (∼30°C). Development increased as water temperatures fell with ripe individuals observed in early winter (∼20°C). Spawning occurred between January and February (winter), when SST were at their coolest (∼18°C). Cytological characteristics of the gonad and averages of oocyte diameters for the different reproductive phases were similar to other geoduck species previously described. Overall sex ratios were equal. This study is the first ecological study to be conducted for P. globosa. Given the development of fisheries for P. globosa and the interest in developing aquaculture for this species, the data provide valuable information for fisheries managers and aquaculturalists and represent the basis for further research on this species.

Morphometric Relationships, Age, Growth, and Mortality of the Geoduck Clam, Panopea generosa, Along the Pacific Coast of Baja California, Mexico

ABSTRACT A commercial fishery for gcoduck Panopea generosa in Baja California began in 2002 and has since achieved landings comparable with those in Washington state and British Columbia, Canada, where geoduck fisheries developed in 1970 and 1976, respectively. This investigation was motivated to acquire the knowledge of population biology of P. generosa at the southernmost extent of its distribution that is required to establish a biological basis for fishery management decisions. This article was further motivated to assess the appropriateness of the current minimum legal size of 130 mm established by the Mexican fishing authorities. Morphometric relationships, age, and growth, and natural mortality of P. generosa were investigated with animals collected from Bahía de San Quintin and Islas Coronado, Baja California, Mexico, collected monthly from April 2008 through January 2009. Ages were obtained by counting growth bands in cross-sections of the shell hinge plate and utilizing cross-dating methods to increase accuracy. Individual P. generosa ages ranged from 3–96 y over both sites. Growth is rapid during the first 10 y and then slows for individuals older than 20–25 y. The asymptotic length was found to be 134 mm, the mean total weight was 764 ± 255 g, the Brody growth coefficient (k) was 0.191, and the natural mortality rate was estimated to range from 0.027–0.046, depending on the method used. These parameter values are similar to those of more northern populations of the same species. Because the proposed minimum legal size is close to the asymptotic length, and considering that geoduck size is difficult to determine before harvest, we suggest that the use of a minimum legal size is not an effective management strategy for geoduck clams.

Status of Geoduck Clam Fisheries in Mexico

ABSTRACT There are 2 species of geoduck fished commercially in northwest Mexico: Panopea generosa, along the Pacific coast of the Baja California peninsula, and Panopea Globosa, in the Gulf of California and in Bahía Magdalena. This study describes the status of the geoduck clam fishery in northwestern Mexico. Recent surveys suggest an ample distribution of beds along both coasts of Baja California and the coast of Sonora. Landings have increased from 49 mt in 2002 to 2,000 mt in 2011. The fishery has a current annual value of approximately US

Reproduction of the Cortes Geoduck Panopea globosa (Bivalvia: Hiatellidae) and Its Relationship with Temperature and Ocean Productivity

30 million, and in Sonora, stock assessments estimate the potential yield to be around 1,800 mt. Fishers in Sonora have expressed an increasing interest to enter into the geoduck fishery, and a total of 1,173,898 pieces have been authorized for new extraction in 2012. We have conducted surveys in 24 beds from February 2009 to October 2011 to evaluate the resource. Given the long life cycles of geoduck, low recruitment and high fishing rates threaten the viability of this resource unless immediate management actions are taken.

Genetic and Morphological Variation of Northeast Pacific Panopea Clams: Evolutionary Implications

ABSTRACT This article describes the timing of gametogenic development and spawning in a population of geoduck clams, Panopea globosa (Dall 1898), from the Upper Gulf of California and its relationship to temperature changes and primary productivity. Clams were collected monthly over 1 year (March 2008 to March 2009), and salinity, dissolved oxygen, and substrate type were recorded during each survey. Standard histological analyses and measurements of oocyte diameters were used to describe the timing of gametogenic development and spawning. Satellite data for temperature and chlorophyll were gathered to test a general conceptual planktonic larval development model. The results demonstrated that reproductive activity was triggered by a steep decrease in temperature 4 months prior to the peak of productivity. Thus, larval development matches favorable conditions, as predicted by Cushings Match—Mismatch Hypothesis.

Estimation of Individual Growth Parameters of the Cortes Geoduck Panopea globosa from the Central Gulf of California using a Multimodel Approach

ABSTRACT Geoduck clams have become the most profitable emerging fishery resource in Northwest Mexico, with profits of more than US

Managing a protected marine area for the conservation of critically endangered vaquita (Phocoena sinus Norris, 1958) in the Upper Gulf of California

30 million during the last few years. The fishery targets two species—Panopea glohosa in the Gulf of California and Panopea generosa on the Pacific coast of Baja California—but is managed indistinctively. Despite its growing importance, scientific research on the basic biology of the Mexican stocks has been inexistent until recently. A major gap in knowledge is the interspecific distinction in structural and functional biological attributes. Consequently, the aim of this article is to provide the biological basis of phenotypic (morphometric) and genetic distinction between P. globosa and P. generosa to assist in their management and conservation. We found that P. generosa from the Pacific coast of Baja California is significantly smaller than P. glohosa from the northern Gulf of California in shell length, width, and height (t-tests, P < 0.0001), and that shell width and height scale differently to length in both species. Multivariate analyses (multidimensional scaling) provided additional support (stress = 0.04) to the species and geographical distinction. Genetic data from the nuclear ribosomal DNA provided contrasting results between polymerase chain reaction— restriction fragment length polymorphisms and direct sequencing. Ribosomal DNA sequences revealed higher diversity (haplotype and nucleotide) in P. glohosa. Standing in sharp contrast with the low intraspecific divergence, was the very large genetic differentiation between species in excess of 20% corrected Kimura 2-parameter sequence divergence and accounting for 98% of the molecular variance of both species. This differentiation was found to be of consequence for novel methods of molecular species identification and for the interpretation of the phylogeography and evolution of Panopea in the North Pacific. The relevance of our findings goes to the heart of filling a major information gap pertaining to the distinction of both species. Scientific and lay stakeholders of these valuable resources need to ascertain and acknowledge this distinction to adopt sustainable management and exploitation practices.

Edad, crecimiento y mortalidad de la almeja de sifón, Panopea globosa (Bivalvia: Hiatellidae) en la región central del Golfo de California, México

ABSTRACT We describe the growth of the Cortes geoduck Panopea globosa (Dall 1898) in the Central Gulf of California using a multimodel approach. Geoducks were collected from November 2008 to February 2010 as part of an experimental fishery off Guaymas, Sonora, Mexico. Their age was established using the acetate peel method. Individual growth was estimated by means of 4 models: von Bertalanffy, logistic, Gompertz, and Schnute. The parameters in each model and their confidence intervals (CIs) were computed using the maximum likelihood method. The best-fitting model was selected using Akaikes information criterion (AIC). According to the AIC, the logistic growth model best describes the growth of P. globosa in this region. We recomputed the CIs of the best model through bootstrapping the model 1,000 times. We found that the asymptotic length of the shell of P. globosa off Guaymas (located in the Central Gulf of California) was 122.2 mm (95% CI, 116.3–128.1) by averaging the asymptotic length estimated in the 3 candidate models (Schnute was not supported). After bootstrapping, the values for the parameters and the first-order corrected 95% CI of the logistic model were L∞ = 122.16 (118.2–124.94), K = 0.497 (0.36–0.614), and t0 = 2.26 (1.599–2.571). We concluded that using a multimodel approach and the AIC represent the most robust method for growth parameter estimation, at least in the studied species.

Integrating genetic, phenotypic and ecological analyses to assess the variation and clarify the distribution of the Cortes geoduck ( Panopea globosa )

We analysed fisheries trends in the northern region of the Gulf of California, within the Biosphere Reserve of the Upper Gulf of California and Colorado Delta River and the Vaquita Refuge Area, and suggest measures to protect the vaquita, Phocoena sinus. We compiled and analysed catch reports of artisanal fishermen in the three fishing communities of the Upper Gulf of California (San Felipe in the State of Baja California, and Golfo de Santa Clara and Puerto Peñasco in the State of Sonora) from 1995 to 2007. This information was categorised with respect to geographic information systems, and all fishing sites within two marine protected areas in the region were identified. In addition, from a survey based on direct interviews with artisanal fishermen in each of the three ports, we identified that 23% of fishermen will continue fishing despite on-going fishing buy-out programmes in the region. We suggest several specific courses of action to decrease the fishing impact on this critically endangered cetacean. However, given the critical situation of this critically endangered species, it is very uncertain whether enforcing a no-take zone within the biosphere reserve and the Vaquita Refuge Area, or even a wider fishing moratorium, will be enough to save this endangered species from extinction.

Selection of Models to Predict Panopea globosa Growth: Application of a Mixture Probability Distribution Function

Debido a la carencia de conocimiento biologico basico de la almeja sifon Panopea globosa, en Mexico, este estudio describe por primera vez la edad y crecimiento de esta especie obtenida desde el Golfo de California. La pesca comercial de almejas sifones (Panopea generosa y P. globosa) comenzo en Baja California en el 2002, con volumenes de captura de 1200 ton a la fecha, lo cual es similar a la pesqueria de este grupo de almejas en otros paises (Washington, Estados Unidos y la Columbia Britanica, Canada) aun cuando la pesqueria se inicio en los anos 70s. Este estudio se realizo con el objetivo de evaluar edad, crecimiento y mortalidad de organismos de P. globosa recolectados en la costa centro oriental del Golfo de California (Bahia del Sol, Sonora, Mexico) entre noviembre 2008 y febrero 2010. La edad se determino mediante el metodo de conteo de bandas de crecimiento en cortes transversales de la concha que es copiado en papel de acetato y ajustando el modelo de crecimiento de von Bertalanffy. La longitud asintotica fue de 122,86 mm con una tasa de crecimiento (k) de 0,33. La mortalidad se estimo con tres diferentes metodos. La mortalidad natural estimada fue de 0,079 a 0,546 segun el metodo utilizado. El intervalo de edad estimado fue de 2-27 anos, pero con mayor representatividad de los individuos de 10 anos. La longitud promedio (± IC α 0,05) de la concha fue de 109,8 ± 3 mm. Los parametros de crecimiento y mortalidad coinciden con los obtenidos en organismos jovenes de otras especies del genero, por lo que concluimos que nuestros resultados aportan evidencia de que la poblacion de la parte central del Golfo de California es de reciente asentamiento en respuesta a un evento ambiental favorable.