**Ecology, Fishery and Aquaculture in Gulf of California, Mexico: Pen Shell** *Atrina maura* **(Sowerby, 1835)**

Ruth Escamilla-Montes, Genaro Diarte-Plata, Antonio Luna-González, Jesús Arturo Fierro-Coronado, Héctor Manuel Esparza-Leal, Salvador Granados-Alcantar and César Arturo Ruiz-Verdugo

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/68135

#### **Abstract**

The pen shell *Atrina maura* bears economic importance in northwest Mexico. This chapter considers a review on diverse ecology, fishery, and aquaculture topics of this species, carried out in northwest Mexico. In ecology, biology, abundance, spatial prospecting, sex ratio, size structure, reproductive cycle, first maturity sizes, variation of gonadosomatic indexes and growth are discussed. In fishery, the information analysed corresponds to the structure of the organisms in the banks susceptible to capture, institutional and ecological interaction for fishing regulation, evaluation of fishing effort, improvement in fishing performance using the knowledge and attitudes of the fishermen on fisheries policies in the Gulf of California, resilience and collapse of artisanal fisheries and public politics. In aquaculture, they are long-line culture, bottom culture, reproductive cycle, growth, production of larvae and seeds, biochemistry of oocytes, nutritional quality of the muscle, evaluation of diets based on microalgae, immunology in larval and juvenile and probiotic use. The present work shows a status based on information published in theses and articles indexed 15 years ago to the date on the ecology, fishery and aquaculture in the pen shell *Atrina maura* carried out in the lagoon systems of northwest Mexico.

**Keywords:** growth, reproduction, culture, immunology, populations, estuaries

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **1. Introduction**

#### **1.1. Taxonomic position**

The taxonomy of the pen shell according to Keen (1971):

Phylum: Mollusca (Linnaeus 1758)

Class: Bivalvia

Subclass: Lamellibranchia

Order: Anisomyaria

Family: Pinnidae

Genus: *Atrina maura* (Sowerby 1835)

Synonymy: *Pinna lanceolata* (G.P. Sowerby 1835)

#### **1.2. Biologic**

#### *1.2.1. Current status*

The Pinnidae ('mussels, scallops, oysters or pen shells') are bivalve marine mollusks that during their life cycle have a planktonic stage and later will incorporate to the benthos where they live until they die. *A. maura* adults measure approximately between 170 and 350 mm, they live in muddy or sandy bottom places, where they strongly attach themselves to the substrate by using their fixation organ; also, due to the proximity of the organisms, they tend to form dense banks by living in groups with other species of lamellibranchs [1]. The shell of these organisms is triangular, reduced in the anterior part and has a pointy shape, whereas the posterior one is a long, flat and well-developed part similar to a wide fan, with a rounded truncated edge, the shape of the shell is strongly influenced by a series of adaptations related to the species life style. The reduction of the anterior part and of the anterior adductor muscle is associated to the substrate fixation by byssal threads, as it occurs with other anisomyarian mollusks [2]. The shell is colonized by a great amount of epibionts that make it look irregular; usually on the shell, there are numerous species of algae, mollusks, polychaetes, bryozoans, ascidians, etc. The outer surface is purplish-amber or dark brown in colour, while the inner surface is shiny [3] (**Figure 1**).

In the Pinnidae, the opening and closing of the valves does not occur in the normal way by the ligament, since the only function of this structure is to keep the valves together; therefore, it takes place by the flexion of the posterior part of the shell, which has high protein content. These organisms have a big posterior adductor muscle located at the central part of the shell (the organism's tissue that is put on the market), as well as a small anterior muscle located at the umbonal vertex. There are two more pairs of muscles that help the movement of the organism's foot, which are the anterior retractor pedals that together with the foot carry out the excavation and motility function [4]. These organisms can even bear the loss of the anterior Ecology, Fishery and Aquaculture in Gulf of California, Mexico: Pen Shell *Atrina maura* (Sowerby, 1835) http://dx.doi.org/10.5772/68135 5

**1. Introduction**

Class: Bivalvia

**1.2. Biologic**

*1.2.1. Current status*

surface is shiny [3] (**Figure 1**).

**1.1. Taxonomic position**

4 Organismal and Molecular Malacology

Phylum: Mollusca (Linnaeus 1758)

Subclass: Lamellibranchia Order: Anisomyaria Family: Pinnidae

The taxonomy of the pen shell according to Keen (1971):

Genus: *Atrina maura* (Sowerby 1835)

Synonymy: *Pinna lanceolata* (G.P. Sowerby 1835)

The Pinnidae ('mussels, scallops, oysters or pen shells') are bivalve marine mollusks that during their life cycle have a planktonic stage and later will incorporate to the benthos where they live until they die. *A. maura* adults measure approximately between 170 and 350 mm, they live in muddy or sandy bottom places, where they strongly attach themselves to the substrate by using their fixation organ; also, due to the proximity of the organisms, they tend to form dense banks by living in groups with other species of lamellibranchs [1]. The shell of these organisms is triangular, reduced in the anterior part and has a pointy shape, whereas the posterior one is a long, flat and well-developed part similar to a wide fan, with a rounded truncated edge, the shape of the shell is strongly influenced by a series of adaptations related to the species life style. The reduction of the anterior part and of the anterior adductor muscle is associated to the substrate fixation by byssal threads, as it occurs with other anisomyarian mollusks [2]. The shell is colonized by a great amount of epibionts that make it look irregular; usually on the shell, there are numerous species of algae, mollusks, polychaetes, bryozoans, ascidians, etc. The outer surface is purplish-amber or dark brown in colour, while the inner

In the Pinnidae, the opening and closing of the valves does not occur in the normal way by the ligament, since the only function of this structure is to keep the valves together; therefore, it takes place by the flexion of the posterior part of the shell, which has high protein content. These organisms have a big posterior adductor muscle located at the central part of the shell (the organism's tissue that is put on the market), as well as a small anterior muscle located at the umbonal vertex. There are two more pairs of muscles that help the movement of the organism's foot, which are the anterior retractor pedals that together with the foot carry out the excavation and motility function [4]. These organisms can even bear the loss of the anterior

**Figure 1.** *Atrina maura* procured from the bottom culture at San Buto estuary in Baja California Sur, México [20].

adductor muscle or even the fusion of the ventral margins of the shell, as long as the posterior part can still be closed by the action of the posterior adductor muscle [5]. The byssus is kept in a chamber found at the posterior basal region of the foot; the bundle of fibrous strands can measure 25 cm in length. The byssus gland is near the area where the foot begins. The soft parts hold a series of characters that differ from other bivalves and are confined mainly in the area between both adductor muscles and overstepping this region, the mantle's lobs and the elongated gills are found, which are extended toward the posterior region, overtaking the adductor muscle [4]. The mantle is attached to the shell as it occurs with other species with similar living habits (some Mytilidae), so it is very retractable without a pallial line. The mantle's retraction confers the family great regeneration ability since all the posterior part of the shell can be rebuilt. The mantle's cavity is divided by a septum that forms the external and internal chambers [5]. The mouth is a tiny orifice located at the anterior portion of the labial lips and continues with the oesophagus, a narrow circular canal that connects with the stomach, where the intestine begins, running toward the posterior area and coming out from the digestive gland, entering the gonad until it reaches the posterior adductor muscle [4]. A very distinctive and unique organ from the Pinnidae family is the pallial organ, whose function has been controversial for a long time. Originally, it was considered as a cleansing organ, in charge of extracting broken pieces from the shell that would remain in the pallial cavity [6, 7]. The heart is located in the dorsal region at the same level as the posterior adductor muscle. The crystalline style begins in the stomach up to the posterior intestine grip, and it secretes enzymes that aid in digestion [8]. The respiratory organ is composed by gills or ctenidia that resemble light brown elongated leaf shape structures which appear in groups of four, located by pairs on each side of the organisms [4]. There are waste ducts that cover the mantle in an anterior-posterior direction, starting from the mouth's palps reaching up to the end of the posterior back part of the gills, completing the division between the inhalant and exhalant chambers.

These canals allow the disposal of pseudofeces and other type of wastes from the inhalant chamber, which can be used to clean the sandy cavity and other residues introduced by the swell before the animal shuts its valves [5]. *A. maura* is a gonochoric organism whose zygotes arise from the union of female and male gametes deriving from those organisms with separated genders. The sexual maturity state can be determined by the gonad's coloration, which sometimes can be observed macroscopically when the valves are opened. The females present a deep orange coloured gonad (like the colour of a brick), and the males have a whitish gonad [9]. The fertilization is external and the larval development is planktonic with trochophore and veliger larvae [10]. The gonads are anastomosed glandular structures that branch out invading the digestive gland. As the maturation progresses, the gonad occupies an even larger space, and it turns out to be more notorious up to the point in which it reaches the typical follicular tubular-acinar system structure that characterizes all bivalves [8, 11].
