**1. Introduction**

294 Aquaculture

Vega, R., Valdebenito I., Barile J., Dantagnan P., Bórquez A. & Mardones, A. (1996). Estado

Chile, 81-84 p.

actual de la investigación y desarrollo de la tecnología para el cultivo comercial del puye *Galaxias maculatus* En: Silva, A. & G. Merino (Eds). Actas IX Congreso Latinoamericano de Acuicultura y 2º Simposio Avances y Perspectivas de la Acuicultura en Chile. Asociación Latinoamericana de Acuicultura, Coquimbo,

#### **1.1 Biological characteristics**

Barnacles belong to the Cirripedia group (*cirri*: cirri, *pedia*: feet) and are, for the most part, sessile crustaceans that live permanently adhered to a substrate that can be inorganic (rock), organic (coral, molluscs, turtles, whales) and even artificial (plastic, wood) (Southward, 1987). They mainly inhabit marine environments; although some species can resist low salinities in estuarine zones (Arenas, 1971), and are distributed bathymetrically from the high intertidal zone to depths of over 1,000 m (Anderson, 1994). They are gregarious, forming dense "patches" of individuals that can completely cover substrates.

The Thoracica superorder is the principal group that assembles the majority of Cirripedia species described. In contrast to other crustaceans, they are characterized by lacking development of the abdomen. This group is divided into three suborders: Lepadomorpha (Fig. 1A), Balanomorpha (Fig. 1B), Verrucomorpha. In general, they present a fragile, chitinous exoskeleton, as a result of which, the majority of species also possess a set of calcareous plates (mural plates and opercular plates) that surround the individual, providing support and defence, as well as, in the case of the opercular valves, associated to feeding, respiration and moulting processes in the specimen. Furthermore, some species have a calcareous base (Southward, 1987).

The thoracic barnacles are filtering organisms with a series of modified articulated appendages, such as a cirral fan, that enables them to capture particles suspended in the water column, feeding, principally, on microscopic algae and the larvae of other invertebrates (Anderson, 1994). These species are simultaneous hermaphrodites, undertaking crossed fecundation or copulation between adjacent individuals by means of elongation of a penis. The ovary is located in the basal part of the organism. After fecundation, the egg mass becomes compact, forming the so called "ovigerous lamellae", within which embryonic and early larval development of specimens occurs. Barnacles incubate eggs within the body cavity up to the larval nauplius I stage, which is released into the water column, initiating a planktonic, free-swimming life that can last two to four weeks. This larval stage, and principally their transport, is influenced by local oceanographic factors, as well as meso and macro-scale processes, such as currents, winds and upwelling (Roughgarden et al., 1988; Gaines and Bertness, 1992; 1993; Pineda, 2000). Larvae grow in size during this stage, increasing the number of appendages and advancing through successive stages (nauplius larvae II to nauplius VI), until converting into the competent larvae denominated *cyprid.* The *cyprid* presents a bivalve form, is lecitotrophic and possesses a sensorial system that enables it to search for an adequate substrate, where texture, colour, quantity of light and biofilm are variables that determine attachment. Immediately after *cyprid* larval settlement, they undergo metamorphosis, adopting the form of an adult specimen, where factors such as depredation, competition and physical disturbances (Gaines & Roughgarden, 1985; Minchinton and Scheibling, 1991, Thomason et al., 1998) play an important role in the early survival of individuals. Under laboratory conditions, it has been described how aspects, such as type and concentration of food, temperature and larval density are key factors influencing duration and survival during larval development (Qiu and Qian, 1999; Mishra et al., 2001; Thiyagarajan et al., 2003a; 2003b). In addition, with respect to induction of larval settlement, it has been observed that a great variety of chemical signals trigger this response, associated, principally, with three types of source: presence of conspecific indivuduals, presence of prey species and microbial films (Rodríguez et al., 1992).

The lepadomorph barnacles ("goose-neck" or "stalked barnacles") are characterized by their fleshy stalk used to adhere to the substrate, as well as calcareous plates, found only in the apical zone of the animal, denominated capitulum. These species mainly inhabit the intertidal zone and are considered neustonic species, adhering to floating structures (Fig.1A). On the contrary, the balanomorph barnacles ("acorn barnacles" or "non-stalked barnacles") do not possess a stalk or peduncle, and adhere directly to the substrate by means of a base that can be membraneous or calcareous. They possess greater development of the calcareous plates, with between 4 and 8 overlapping plates that form a supporting

Fig. 1. General view of the barnacles. A. Lepadomorpha. B. Balanomorpha.

within which embryonic and early larval development of specimens occurs. Barnacles incubate eggs within the body cavity up to the larval nauplius I stage, which is released into the water column, initiating a planktonic, free-swimming life that can last two to four weeks. This larval stage, and principally their transport, is influenced by local oceanographic factors, as well as meso and macro-scale processes, such as currents, winds and upwelling (Roughgarden et al., 1988; Gaines and Bertness, 1992; 1993; Pineda, 2000). Larvae grow in size during this stage, increasing the number of appendages and advancing through successive stages (nauplius larvae II to nauplius VI), until converting into the competent larvae denominated *cyprid.* The *cyprid* presents a bivalve form, is lecitotrophic and possesses a sensorial system that enables it to search for an adequate substrate, where texture, colour, quantity of light and biofilm are variables that determine attachment. Immediately after *cyprid* larval settlement, they undergo metamorphosis, adopting the form of an adult specimen, where factors such as depredation, competition and physical disturbances (Gaines & Roughgarden, 1985; Minchinton and Scheibling, 1991, Thomason et al., 1998) play an important role in the early survival of individuals. Under laboratory conditions, it has been described how aspects, such as type and concentration of food, temperature and larval density are key factors influencing duration and survival during larval development (Qiu and Qian, 1999; Mishra et al., 2001; Thiyagarajan et al., 2003a; 2003b). In addition, with respect to induction of larval settlement, it has been observed that a great variety of chemical signals trigger this response, associated, principally, with three types of source: presence of conspecific indivuduals, presence of prey species and microbial

The lepadomorph barnacles ("goose-neck" or "stalked barnacles") are characterized by their fleshy stalk used to adhere to the substrate, as well as calcareous plates, found only in the apical zone of the animal, denominated capitulum. These species mainly inhabit the intertidal zone and are considered neustonic species, adhering to floating structures (Fig.1A). On the contrary, the balanomorph barnacles ("acorn barnacles" or "non-stalked barnacles") do not possess a stalk or peduncle, and adhere directly to the substrate by means of a base that can be membraneous or calcareous. They possess greater development of the calcareous plates, with between 4 and 8 overlapping plates that form a supporting

Fig. 1. General view of the barnacles. A. Lepadomorpha. B. Balanomorpha.

**A B**

films (Rodríguez et al., 1992).

structure. Furthermore, two pairs of plates are located in the upper zone, forming the opercule (terga and scuta) (Fig. 1B). These species are habitual members of the shallow intertidal and subtidal communities of the coastal area. Finally, the verrucomorph barnacles ("wart barnacles") are small organisms, without a peduncle, characterized by their asymmetric opercular plates, and are more frequent in deep-waters, where they appear as epizoos of other invertebrates (Anderson, 1994).

#### **1.2 Commercially important barnacle species worldwide**

In spite of the wide variety of barnacle species on a global scale, only a few are commercially important, due to the small size of the majority of these organisms (Table 1). Of the lepadomorph barnacles, *Pollicipes pollicipes* (Leach, 1817), the "goose neck barnacle", is the best known culinary resource. It is extracted along the coasts of Galicia (Spain) by fishermen´s organizations, known as unions ("perceberos"), and can reach a height of 10 to 12 cm. Approximately 300-500 ton/year are captured, and demand is high (Molares &


Table 1. Commercially important barnacle species and species used for human consumption worldwide. Scientific and common names, geographic distribution and production types. Source: Modified from López et al., (2010).

Freire, 2003). Overexploitation of natural banks of this resource has prompted regulation of extraction activity. Other species of the same genus, such as *P*. *polymerus* (Sowerby, 1833) and *P. elegans* (Lesson, 1830), are commercially significant on a local scale in Canada and Perú, respectively, and, secondarily, are used to supply the Iberian market (Bald et al., 2006; Jacinto et al., 2010). On the other hand, the species *Capitulum mitella* (Linnaeus, 1758) or "stalked barnacle", distributed along the southern coast of Japan, is smaller (< 5 cm height) and is only consumed on the local market.

Of the balanomorph barnacles (Table 1), the most commercially important species is *Austromegabalanus psittacus* (Molina, 1782) "picoroco" or "giant barnacle" a large species that can reach a height of 30 cm. Distribution ranges from southern Perú to the austral zone of southern Chile and the southern coast of Argentina (Pilsbry, 1916; Young, 2000, López et al., 2007a). It is exploited on a small scale by artisanal fisheries and catches are concentrated in southern Chile (42oS), with landings that fluctuate between 200-600 ton/year (Fig. 2). Average commercial size is 2.2 cm carino rostral length. Another giant species is *Balanus nubilus* (Darwin, 1854), distributed along the Pacific coast, from Alaska to North America, and consumed by indigenous coastal communities (Morris et al., 1980). *Megabalanus azoricus* (Pilsbry, 1916) "craca", is a subtidal species, limited to the Azores Islands archipelago (Portugal), in the Atlantic Ocean (Southward, 1998; Regala, 1999; Santos et al., 2005). It is exploited locally, and specimens over 1 cm carino rostral length are consumed fresh (Lotaçor, 2006; Pham et al., 2008). The analysis of the enterprises LOTAÇOR S.A data, from 1980 to 2010 shows that reported landings are modest, ranging from 1 to 3.3 ton/year on the 80´s, stabilized bellow 1ton/year in the 90´s, have raised considerably between 1999 to 2003, when a historic maximum of 7ton/year was auctioned. Since 2003 the landings have been dropping to about 3.7ton/year in 2010. From 2005 to 2010, the average first selling price has been around 3.90€/kg, with a minimum of 0.20€/kg and a maximum of 20€/kg. The real catches and economic value of the resource may be substantially higher than the reported. The species is highly appreciated locally, and traditionally caught along the shores, by the people and for their own consumption. Dionisio et al., (2009), based on LOTAÇOR data, described some socio-economic aspects of this fishery and estimate a *per-capita* consumption between 88 and 241g/year. The *Megabalanus tintinnabulum* (Linnaeus, 1758) "claca" species is extracted in the Madeira archipelago (Portugal), and the Canaries (Spain). It is a cosmopolitan species whose distribution covers the entire tropical zone of the Pacific, Atlantic and Indian oceans (Young, 1998).

In the Japanese market, balanomorph barnacles are referred to as "fujit-subo". In northern Japan, mainly in the Aomori prefecture, the *Balanus rostratus* (Hoek, 1833) "mine fujit-subo" is commercialized, and can reach a height of 5 cm, with landings of around 10 ton/year. Other smaller species of balanomorph barnacles, *Megabalanus rosa* (Pilsbry, 1916) "aka fujitsubo" and *Tetraclita japonica* (Pilsbry, 1916); "kuro fujit-subo", are also extracted locally in the central-southern zone of Japan. Similarly, in Indonesia the *Tetraclita kuroshioensis* Chan, Tsang & Chu, 2007, "hat fujit-subo", is consumed by coastal communities.

#### **2. State of barnacle culture on a world scale**

In spite of the commercial importance of various species of barnacles, development of activities associated with cultures is limited to a few species (López et al., 2010). Among the lepadomorphs, previous information on *Pollicipes pollicipes* is available related to obtaining

Freire, 2003). Overexploitation of natural banks of this resource has prompted regulation of extraction activity. Other species of the same genus, such as *P*. *polymerus* (Sowerby, 1833) and *P. elegans* (Lesson, 1830), are commercially significant on a local scale in Canada and Perú, respectively, and, secondarily, are used to supply the Iberian market (Bald et al., 2006; Jacinto et al., 2010). On the other hand, the species *Capitulum mitella* (Linnaeus, 1758) or "stalked barnacle", distributed along the southern coast of Japan, is smaller (< 5 cm height)

Of the balanomorph barnacles (Table 1), the most commercially important species is *Austromegabalanus psittacus* (Molina, 1782) "picoroco" or "giant barnacle" a large species that can reach a height of 30 cm. Distribution ranges from southern Perú to the austral zone of southern Chile and the southern coast of Argentina (Pilsbry, 1916; Young, 2000, López et al., 2007a). It is exploited on a small scale by artisanal fisheries and catches are concentrated in southern Chile (42oS), with landings that fluctuate between 200-600 ton/year (Fig. 2). Average commercial size is 2.2 cm carino rostral length. Another giant species is *Balanus nubilus* (Darwin, 1854), distributed along the Pacific coast, from Alaska to North America, and consumed by indigenous coastal communities (Morris et al., 1980). *Megabalanus azoricus* (Pilsbry, 1916) "craca", is a subtidal species, limited to the Azores Islands archipelago (Portugal), in the Atlantic Ocean (Southward, 1998; Regala, 1999; Santos et al., 2005). It is exploited locally, and specimens over 1 cm carino rostral length are consumed fresh (Lotaçor, 2006; Pham et al., 2008). The analysis of the enterprises LOTAÇOR S.A data, from 1980 to 2010 shows that reported landings are modest, ranging from 1 to 3.3 ton/year on the 80´s, stabilized bellow 1ton/year in the 90´s, have raised considerably between 1999 to 2003, when a historic maximum of 7ton/year was auctioned. Since 2003 the landings have been dropping to about 3.7ton/year in 2010. From 2005 to 2010, the average first selling price has been around 3.90€/kg, with a minimum of 0.20€/kg and a maximum of 20€/kg. The real catches and economic value of the resource may be substantially higher than the reported. The species is highly appreciated locally, and traditionally caught along the shores, by the people and for their own consumption. Dionisio et al., (2009), based on LOTAÇOR data, described some socio-economic aspects of this fishery and estimate a *per-capita* consumption between 88 and 241g/year. The *Megabalanus tintinnabulum* (Linnaeus, 1758) "claca" species is extracted in the Madeira archipelago (Portugal), and the Canaries (Spain). It is a cosmopolitan species whose distribution covers the entire tropical zone of the Pacific,

In the Japanese market, balanomorph barnacles are referred to as "fujit-subo". In northern Japan, mainly in the Aomori prefecture, the *Balanus rostratus* (Hoek, 1833) "mine fujit-subo" is commercialized, and can reach a height of 5 cm, with landings of around 10 ton/year. Other smaller species of balanomorph barnacles, *Megabalanus rosa* (Pilsbry, 1916) "aka fujitsubo" and *Tetraclita japonica* (Pilsbry, 1916); "kuro fujit-subo", are also extracted locally in the central-southern zone of Japan. Similarly, in Indonesia the *Tetraclita kuroshioensis* Chan,

In spite of the commercial importance of various species of barnacles, development of activities associated with cultures is limited to a few species (López et al., 2010). Among the lepadomorphs, previous information on *Pollicipes pollicipes* is available related to obtaining

Tsang & Chu, 2007, "hat fujit-subo", is consumed by coastal communities.

and is only consumed on the local market.

Atlantic and Indian oceans (Young, 1998).

**2. State of barnacle culture on a world scale** 

Fig. 2. "Giant barnacle" in a local market in Puerto Montt city, southern Chile.

juveniles in artificial floating substrates (Goldberg, 1984). Results have been scarce, mainly because, in this species, larval settlement is determined by the presence of conspecific adults (Molares et al., 1994; Cruz et al., 2010). Among balanomorph barnacles, similar experiments have been undertaken on *Megabalanus azoricus* in the Azores islands, where technologies have been designed for installing collectors in the water column. The results indicate that larval settlement occurs, although it is still not possible to ensure that levels are sufficient for industrial scale cultures (Pham et al., 2008; Pham & Silva, 2010; López et al., 2010). Thus, progress has been made, on an experimental level, with these two species, in the area of spat collection from the wild. The only species where studies have advanced from experimental to semi-industrial cultures, is the "giant barnacle","picoroco", *Austromegabalanus psittacus*, on the Chilean coast. In this species, it has been shown that levels of spat collection from the wild will permit the development of commercial cultures. Similarly, the growth rates enable specimens of a commercial size to be obtained over a short period of time (López, 2008; López et al., 2010). Furthermore, low cost production technologies have been developed to obtain spat and to enhance growth. The yield and economic feasibility of various products have also been evaluated (Bedecarratz et al., 2011).

In *Megabalanus azoricus*, culture activities are incipient. This species is an intertidal barnacle found strictly in areas characterized by strong water flows around the Azorean coastline. It is a highly appreciated shellfish, whose natural populations are subject to intense exploitation (Santos et al., 1995). As a result, the regional authorities have identified the need to conduct trials with a view to developing aquaculture technologies for this species (Pham et al., 2008). Initial results for this species are encouraging (Pham et al., 2011), but much more research is required.

One aspect critical to barnacle species culture is present levels of knowledge with regard to: the particular biological characteristics of life cycle; the dispersion and behaviour of competent larvae, as well as ecological and functional aspects of juveniles during growth. From experiences undertaken to date, the main difficulties affecting culture are the following: (a) juveniles cannot be obtained from the wild, or can only be obtained in very limited quantities. It may also be possible to procure juveniles through larval cultures in hatcheries; however this increases costs considerably. The limited amount of spat obtained from the wild can be associated with various aspects, such as: - low supply of competent *cyprid* larvae; - substrates that are inadequate for the exploratory and attaching behaviour of the competent *cyprid* larvae; - lack of synchronization between period of maximum competent larvae quantities and the installation of artificial substrates (spat collectors) in the water column; - high spatial and temporal variation in spat collection, associated with climatic, oceanographic and topographic factors (Goldberg, 1984; Lagos et al., 2008; Andrade et al., 2011). (b) high levels of unpredictability in competent larvae supplies, that operate on a macro and meso-scale in the ocean. Consideration must be given to the fact that barnacles can form metapopulations and larval dispersion can be very wide (Lagos et al., 2005); (c) problems during growth related to the presence of predators or species that compete for the substrate or food (Pham & Silva, 2010); (d) density-dependent effects associated with mass recruitment (Hills & Thomason, 2003); (e) heavy weight of the shell, that occurs mainly in balanomorphs species. This also generates low harvest yields.

On the other hand, the main advantages associated with the biological characteristics of the barnacle species are: (a) possibility of obtaining spat from the wild; (b) gregarious larval settlement, which, if suitable substrates are available, can ensure an adequate supply of spat; (c) internal embryonic development in the case of balanomorphs barnacles, that limits early mortality and d) filter feeding, that permits suspended cultures without provision of exogenous feed.

Future projections for barnacle culture are aided by the wide-ranging and diversified literature available on larval development in various species; specifically, on aspects such as: duration, effects of environmental factors and feeding, as well as ecological, physiological and behavioural factors associated with larval settlement and recruitment (Walker, 1995; Jenkins et al., 2000; Dionisio et al., 2007; Tremblay et al., 2007; Pineda et al., 2009). Although this information is mainly related to species that are not commercially important, it can be used to optimize barnacle culture.
