1. IDENTITY
2. DISTRIBUTION, ECOLOGY AND METABOLISM
3. LIFE HISTORY
4. POPULATION STRUCTURE AND MORTALITY
5. PRODUCTIVITY OF THE RESOURCE
6. HARVEST METHODS
7. EQUIPMENT USED FOR HARVESTING AND CULTURE OF RESOURCES
8. PROTECTION AND MANAGEMENT OF THE CROP
9. UTILIZATION
10. REFERENCES
by
Bernabe Santelices
Departamento de Biologia Ambiental y de Poblaciones
Facultad de Ciencias Biologicas
P. Universidad Catolica de Chile
Casilla 114-D; Santiago, Chile
|
ABSTRACT Gelidium chilense, G. lingulatum and G. rex are economically important in Chile. Gelidium lingulatum extends from central to southern Chile (33 to 41 S) while the two other species extend from central Chile to central Peru (35 to 14 S). All three species occur in low intertidal belts along the more wave exposed rocky coasts. Light intensity, temperature, water movement and interspecific interference have been proven to be ecologically important in regulating distribution and production. Daily growth rates of 2.5 to 4 percent have been reported. The Chilean wild crops (100 - 150 tons per year) are a minor part of the world crop of Gelidium-Pterocladia (15,000 to 19,000 tons per year). Gelidium rex has grown 2.5 to 3 percent per day in experimental field cultivation. Gelidium chilense is able to grow under free floating conditions. All three are gathered by hand picking as a part-time activity. |
1.1.1 Valid scientific name
In Chile, three species of Gelidium are economically important, Gelidium chilense (Montagne) Santelices et Montalva, G. lingulatum Kutzing and G. rex Santelices et Abbott.
1.1.2 Nomenclatural synonyms
The basionym of Gelidium chilense is Acropeltis chilensis Montagne (1837, p. 355). Previous to clarification this common species of Gelidium in Central Chile (Santelices and Montalva, 1983; Santelices and Abbott, 1985) passed under the name of G. filicinum Bory (Montalva and Santelices, 1981; Santelices, Oliger & Montalva 1981).
Gelidium lingulatum was originally conceived by J. Agardh, who gave it the manuscript name Suhria lingulata. Yet, it was first described by Kutzing (1868, p. 27, fig. 65). J. Agardh published further descriptions in 1872 and 1876. The species was found in Chile by Montagne (1852, p. 330) but misidentified as G. filicinum Bory, an opinion also held by Navas (1966). Skottsberg (1923, p. 5) and Levring (1960, p. 34) have confused Chilean materials of G. lingulatum with G. crispum Howe.
The recently described Gelidium rex Santelices and Abbott (1985, p. 33) had been referred to previously as G. spinolosum Kutzing prox. (Oliger and Santelices, 1981; Montalva and Santelices, 1981; Santelices, Oliger & Montalva 1981).
1.1.3 Vernacular name
In Chile fishermen refer to the various species of Gelidium under the common name of "chasca".
1.2.1 Affinities
1.2.1.1 Suprageneric
The genus Gelidium belongs to the family Gelidiaceae, which also includes eight other genera. The family Gelidiaceae has been considered a member both of the order Gelidiales and of the Nemalionales (=Nemaliales). The classification of the family depends upon acceptance of the Gelidiales as a distinct order, a taxonomic status which has been under dispute over the last twenty years (Dixon, 1961; Papenfuss, 1966; Pueschel and Cole, 1982).
1.2.1.2 Generic
The genus Gelidium was established by Lamouroux (1813) with the European species Gelidium corneum (Hudson) Lamouroux as the Type. The following is a diagnosis of the genus.
The thallus is cartilagineus, sometimes crispate, 2 to 40 cm tall, composed of one or several erect terete or compressed axes. Axes distichously, plumosely or irregularly branched, red to deep purple although in some species deep green, blackish or caeru-lean. Erect axes arise from cylindrical or compressed, branched or unbranched creeping axes with numerous short haptera extending as individual axes or forming massive disc-like holdfasts. Plants sometimes occurring in mats of algal turf with extensive basal parts or in rather discrete clumps. The erect fronds can be cylindrical at the base, subcylindrical above and frequently compressed at their apical ends. Margins of the axes can be entire or subentire. Often they are subentire in the basal third, irregularly sinuous-dentate or erase dentate above and variously branched along the edges of the upper half of the erect axes. Cortex with several rows of pigmented cells, generally smaller towards the outside, mostly 2-15 m m diam., generally irregularly arranged in surface view. Medullary cells in cross section generally rounded, up to 30 m m diam., colorless, compact or loosely appressed, with or without evident starch granules. Rhizoidal filaments thick-walled, up to 5 m m diam., in medullary and/or cortical tissues, varying in number and position within species. Tetrasporangia in sori occupying the entire or the somewhat expanded or broadly rounded tips of lateral branches or main axes. Fertile branches simple or pinnately compound, somewhat twisted and densely congested. Often with sterile margins. Tetrasporangia cruciately divided, up to 35 m m and generally arranged without order in the sori. Spermatangial sori sometimes apparent as relatively unpigmented areas on apices of branchlets, usually conspicuous by presence of a sterile darker margin. Carpogonial filaments unicellular, fusing with adjacent cells after fertilization. Mature cystocarp protruding equally on both surfaces of the branch, usually with one or, more rarely, several openings on each surface of the frond. Occasionally two cysto-carpic cavities coalesce laterally, forming compound cystocarps up to 1 mm long.
It should be noticed that cystocarpic structure is the only presently accepted morphological difference distinguishing Gelidium from the closely related genus Pterocladia. However, due to the common scarcity of sexual thalli this character is of limited application for routine taxonomic purposes. Other morphological characters have been suggested as segregation characters (Okamura, 1934; Akatsuka, 1981; Stewart, 1976), including hyphal distribution, shape of medullary and cortical cells and degree of basal incurvation of branches and branchlets but they have not recieved general recognition (see Santelices, 1974 for a review).
1.2.1.3 Specific
The Type specimen of Gelidium chilense was collected at Coquimbo, central Chile (30°S), and is now deposited in the Montagne Herbarium, Museum National d'Histoire Naturelle, Paris (Santelices and Montalva, 1983). The Lectotype of Gelidium lingulatum Kutzing is a plant labelled 'Herbarium Kutzing No. 46' deposited at the Rijksherbarium, Leiden. Previously; the specimen No. 33241 in Herb. Agardh, University of Lund, identified by J. Agardh had been chosen as lectotype by Levring (1960). Both plants probably came from the same place in southern Chile in the proximity of Valdivia (Santelices and Montalva, 1983).
The holotype of Gelidium rex Santelices et Abbott bears the Herbarium No. 102652 and is deposited in the Museo Nacional de Historia Natural in Santiago, Chile. Isotypes have been deposited in the Herbarium of the Sala de Sistematica, Pontificia Universidad Catolica de Chile (SS UC), the Algal Collection of the U.S. National Herbarium/Smithsonian Institution, Washington, D.C. (U.S.A.), and the Herbarium of the B.P. Bishop Museum, Honolulu, Hawaii (U.S.A.). All plants were collected from their normal low intertidal to high subtidal habitats, among holdfasts of Lessonia nigrescens Bory, at Pelancura (ca 5 Km north of San Antonio Port) Santiago Province, Chile, on a wave-exposed rocky platform (Santelices and Abbott, 1985).
The plants of Gelidium chilense are composed (Fig. 1a) of several erect, flat axes similar to a sword blade but with rounded and somewhat widened apices. Attachment is by a cylindrical creeping axis with stolons at irregular intervals. Branches can be found along most of the axis, although they are scarce in the basal third. Branching can be of up to three orders. First-order branches are similar to the main axis, frequently disposed in an irregular manner and generally producing second-order or terminal, ovate-lanceolate branchlets. Often first order branches end in a truncate (grazed) apex whence a group of ovate-lanceolate or heart like branchlets originate.
A transection of the frond (Fig. 2a) shows a cortex of 2-3 layers of globose-ovoid pigmented cells with their diameters less towards the medulla. The medulla is composed of colorless cells of up to 20m m diameter. Rhizoidal filaments are extremely abundant in inner cortex and outer parts of the medulla, decreasing in density towards the inner medulla.
Tetrasporangia are produced in short, heart-like, rounded or irregularly shaped proliferations, commonly with toothed or dentate margins or on rounded and somewhat expanded apices of main axes (Pig. 3a). They are globose-ovoid, 10-30 m m diam. and 20-50 m m long, cruciately divided. Cystocarps are borne on small, rounded branchlets with dentate margins (Fig. 4a). They are ovoid in surface view, up to 600 m m thick and 800 m m long, with two locules, each with one or two ostioles opening on each surface of the frond.
Figure 1. External morphology of the three economically important species of Gelidium in Chile.
The plants of Gelidium lingulatum in Chile grow to 12 cm tall and are attached to the substratum by short, irregularly disciform holdfasts (Fig. 1b). The erect axes are cylindrical and simple or sparingly branched near the base. Upwardly they are strap-shaped (2 mm broad x 200 m m thick), with flat marginal branches in the upper parts disposed in an irregularly alternate or almost digitate manner. The larger branches resemble the erect axes, while the smaller are irregularly shaped. The margins of main axes and primary branches often have branch rudiments.
Figure 2. Transections of fronds of Gelidium chilense, G. lingulatum and G. rex.
A transection through the flat, erect axis shows (Fig. 2b) a cortex with three to four layers of rounded, pigmented cells of 5-15 m m diam., inwardly increasing in size and decreasing in pigmentation. Rhizoidal filaments are not very abundant and are scattered in the inner cortex and medulla.
Tetrasporangia and cystocarps occur in pinnately or subpin-nately arranged proliferations (Figs. 3b and 4b) that are irregularly compound, commonly crisped or contorted and with serrate margins. Tetrasporangia are ovoid, cruciately divided, 16-25 m m diam. and 19-38 m m long. Cystocarps are elongate, up to 800 m m thick and 1 mm long, with an ostiole on each side of the frond.
The thallus of Gelidium rex is rigid, crispate and cartilaginous, up to 30 cm tall, consisting of one to several erect axes devoid of branches in the basal half and irregularly branched in the apical portion of the thallus (Fig. 1c). Erect axes arising from cylindrical creeping axes that have downward projecting numerous short haptera that form massive discoid holdfasts. Erect axes cylindrical at the base, flattened above and slightly compressed at the apical end; to 2 mm wide, 0.8 mm thick at the cylindrical base. Margins of axes and branches conspicuously dentate, particularly in upper portions. Branches in young specimens and in sterile adult plants scarce, generally of one order, disposed alternately along the axis and externally similar to the erect axes. Fertile thalli abundantly branched in their upper third and consisting of axes of elongated, bladelike branches with margins conspicuously dentate. Fertile branchlets lobate, or pinnately compound.
Cortex of erect axes (Fig. 2c) of 4-6 pigmented cell layers, the most external cortical layer conspicuous, of cuboidal cells with rounded corners, to 12 m m high by 8 m m diam.; inner cortical cells increase slightly in size inwardly, surrounded by numerous, colorless, rhizoidal filaments. Medullary cells rounded and ovoid in transection, to 30 m m diam., with extremely thick cell walls; rhizoidal filaments scarce in inner medulla.
Figure 4. Fertile female branchlets and cystocarpic structure in Gelidium chilense, G. lingulatum and G. rex.
Tetrasporangia cruciate, 20-40 m m diam., arranged without order in sori on single or pinnately compound fertile branchlets, with dentate margins (Fig. 3c). Cystocarps on pinnately compound, somewhat twisted and densely congested branches (Fig. 4c), ovoid, about 0.5 mm in surface view, up to 0.7 mm thick, with one or, more rarely, several openings on both surfaces of the frond.
It should be noted that all three species and especially G. chilense and G. lingulatum have several morphological variants which appear under different environmental conditions.
2.1 Geographic extent
2.2 Local vertical and horizontal distribution
2.3 Effects of ecological determinants
2.4 Nutrition and growth
Gelidium chilense and G. rex have an approximately similar geographic distribution. Gelidium chilense extends from 14°S in central Peru to approximately 35°S in central Chile. Likewise, G. rex has been found from southern Peru (ca 16°S) to southern (40°S) Chile (Santelices and Montalva, 1983; Santelices and Abbott, 1985).
Gelidium lingulatum has been repeatedly collected from Valparaiso, in Central Chile (ca 33°S) to Puerto Montt (41°S). Levring (1960) also reported the species from the Strait of Magellan (53°S) but the species has not been found there again.
All three species of Gelidium occur as belts around the lower limits of the spring tides on rocky bottoms in exposed and semi-exposed habitats.
In the rocky intertidal of central Chile, Gelidium chilense and Gelidium lingulatum occur (Fig. 5) at the same tidal elevations with no evidence of zonation or other type of spatial segregation between them although G. chilense extends slightly higher and lower than G. lingulatum. Gelidium rex occurs in low intertidal to high subtidal clumps of plants, sometimes forming a belt, and is frequently under the shade of the kelp Lessonia nigrescens (Oliger and Santelices, 1981; Montalva and Santelices, 1981).
Figure 5. Vertical distribution of Gelidium chilense, G. lingulatum and G. rex in wave exposed, rocky habitats of Central Chile.
Gelidium chilense is the species with most widespread distribution. It is most abundant on rocky intertidal shaded surfaces directly exposed to strong waves. Yet, the species also occurs on boulders where it forms a low turf. Infrequently it inhabits sheltered, middle intertidal pools where the plants have elongated, almost cylindrical creeping axes pinnately branched to three orders.
Gelidium lingulatum also is abundant on rocky intertidal surfaces exposed to strong waves. However, the species is most abundant and reaches larger sizes in middle intertidal pools with frequent water exchange. When growing on barnacles and mussels on wave exposed, vertical walls, G. lingulatum is rather rigid, sparingly and often irregularly branched below, irregularly 1-2 pinnately branched above.
Gelidium rex has the least widespread ecological distribution. It occurs only on shallow subtidal shaded rocky surfaces exposed to very strong waves and high water exchange rates.
Available data (see Santelices, 1974 and 1978 for reviews) point to general patterns of ecological responses for the species of Gelidium. They occur on rocky substrata, often on top of coralline crusts, normally associated with high levels of water movement, extending up to 1.5 m of intertidal elevation and down to 25 m deep. Their standing crop is maximal in shaded habitats and during summer. In Temperate latitudes seasonal growth is correlated with temperatures while in Tropical waters growth is correlated best with light intensity and water movement. Laboratory studies have confirmed these as low light saturation species. Growth can be increased by temperature increments up to 25°C or by long photoperiods combined with low light intensities. Increments in water movement or nutrient enrichments (especially nitrogen and phosphorus) can reverse to some extent the bleaching effects of high light and high temperatures. Grazing and interspecific interference often seem to affect field productivity but few quantitative data exist on this matter.
The few ecological studies performed with the three Chilean species of Gelidium (Oliger and Santelices, 1981) have shown that they have temperature tolerance ranges from 10 to 25°C. Growth does not occur above and below these limits (Oliger and Santelices, 1981). Growth rates are maximum at 20°C for Gelidium chilense and at 15°C for G. ligulatum and G. rex (Fig. 6).
The combined effects of light intensity and photoperiod affect in various ways the above three species (Fig. 6). The lower intertidal Gelidium rex is the species with the least tolerance to extended photoperiods under the higher experimental quantum dose used in these studies (120 m Em-2S-1). Growth under photoregimes of 16 h of daily light is achieved only when the quantum dose is reduced to 45 m Em-2S-1. By contrast, the middle intertidal species G. lingulatum and G. chilense will maintain their optimal growth rates under conditions of higher quantum dosage and long days (16 hours of daily light). None of the three species could survive in continuous light as, in all experiments, the thalli normally bleached under long day regimes of 24 hours of light.
Physiological ecological responses of sporelings to different temperature-light regimes are somewhat different from the responses shown by adult thalli (Correa et al., 1985). Both, in Gelidium chilense and G. lingulatum the sporelings are light-saturated at 50 m Em-2S-1. In the case of G. chilense maximum growth of the sporelings requires a shorter photoperiod (12 h) than the mature thalli. These findings are consistent with predictions indicating that mature plants should have greater light requirements than those of sporeling stages because of their increased proportions of non-photosynthetic internal tissues.
Field studies with Gelidium chilense and G. lingulatum in the rocky intertidal habitats of Central Chile have stressed the importance of interspecific interactions in the distribution of these species (Santelices, Montalva & Oliger 1981). As previously indicated, in these habitats both species of Gelidium occur at the same tidal levels with no evidence of zonation or other type of spatial segregation between them. Both are perennial (Montalva and Santelices, 1981). Gelidium lingulatum is maximally abundant in summer; the peak being correlated with temperature and photoperiod. The stocks of G. chilense, by contrast, scarcely vary seasonally. Temporal standing stock changes in this species, however, were significantly negatively correlated with the stocks of G. lingulatum. The negative correlation occurred at each of the three intertidal levels studied and the significance increased from the higher to the lower levels. Since in both species there was a direct correlation between total standing stock and tetrasporangial standing stock, the interspecific interaction affected their reproductive potentials (Montalva and Santelices, 1981).
Gelidium chilense also can interact with Lessonia nigrescens at low intertidal levels and the outcome of the interaction is heavily depending on season. Gelidium chilense is fertile all year round whereas the sporophyte of L. nigrescens is fertile only during late winter. If the kelp is removed during late fall or early winter, G. chilense temporarily extends into the low intertidal levels previously occupied by L. nigrescens. Yet, the newly settled juveniles of the kelp start appearing by the end of winter and are able to overgrow, shade and cover the thalli of G. chilense with their massive holdfasts (Santelices and Ojeda, 1984; Ojeda and Santelices, 1984). By contrast, if the kelp is removed in summer there is a 4-5 months of time for the growth and expansion of G. chilense without the juveniles of L. nigrescens. Under these circumstances the settlement of L. nigrescens expected to occur in August does not occur due to monopolization of the primary substratum by G. chilense.
Little is known of the nutritional requirements of the three Chilean species of Gelidium. Experimental studies with other species in the genus have shown that fertilization with ammonium or with nitrate increases pigment concentration and promotes growth. The effect is more pronounced if the additions are made in the presence of phosphorus (see Santelices, 1974 for a review). Some species can simultaneously assimilate ammonium and nitrate. The addition of NaHCO3 to the culture medium has been found to increase productivity still further.
The species of Gelidium are supposed to have a "Polysiphonia type" of life history with equal proportions of tetrasporic and asexual generations (Kylin, 1923). Indeed/the occurrence of sexual and tetrasporic phases has been confirmed in several species of Gelidium (see Santelices, 1974 for a review). Nevertheless, it is quite common to find field differences in proportions of tetrasporangial to sexual thalli. Tetrasporangial thalli often are several orders of magnitude more frequent or more abundant than sexual thalli. And this is the case both for G. chilense and G. lingulatum from Central Chile, where the biomass of sexual thalli throughout the year amounted to less than 10% of the fertile biomass (Montalva and Santelices, 1981).
Two hypothesis have been advanced to explain the differences in ratio of sexual to tetrasporic thalli. Based on life history studies of British species of Gelidium, Dixon (1961) suggested that local variations in the life history could be considerable and that meiosis may not be occurring in all sporangia of a given sporophyte. Alternatively, based on results reported by Yamasaki and Osuga (1960) from Japan, Santelices (1974) suggested intra-specific competition between tetrasporic and sexual thalli. Increased sensitivity to environmental parameters and reduced competitive ability could be expected to occur in the sexual, haploid phase while increased vigor could be expected to occur in the diploid thalli, leading to the possibility of a gradual replacement of haploid by diploid thalli in the field. More recently, Barilotti (1960) has agreed with this hypothesis although he has stressed that no direct survivorship difference has been found experimentally between the two phases, nor has there been an experimental evaluation of the importance of reproductive effort leading to diploid dominance performed for any species of Gelidium.
Reproduction has been found to be a seasonal phenomenon in many species of Gelidium and it is generally assumed to be temperature regulated (see Santelices, 1974 for a review). However, the two species of Chilean Gelidium so far studied are an exception to this trend. As discussed previously, tetraspore formation in Gelidium chilense and G. lingulatum is affected by interspecific interference. Cystocarp production in both species occurs during the whole year (Montalva and Santelices, 1981).
Spore germination has also been shown to be influenced by temperature in several species of Gelidium (Santelices, 1974). However, laboratory experiments with the two Chilean middle intertidal species indicate that temperatures ranging from 10 to 20°C, three different photoperiodic regimes and photon-flux densities from 25 to 75 m Em-2S-1 do not induce significant differences in germination values of G. lingulatum or G. chilense (Correa et al., 1985).
4.1 Population structure
4.2 Sporophyte - gametophyte and sex composition
4.3 Density
4.4 Mortality - morbidity
No study has been performed yet trying to understand the population structure of any of the three Chilean species of Gelidium. However a few ideas emerging from studies in other populations of Gelidium elsewhere are perhaps relevant.
Because vegetative propagation is common in the genus, the basalmost portion of the erect axes as well as the creeping axes might be several years old. Therefore, age composition can be studied only in natural populations of erect axes. Yet these axes generally are slow growers and frequently they are either too small or too weak to tolerate tagging for extended periods. Therefore, approximations to population structure of Gelidium communities have been attempted through the study of size distribution of fronds (Silverthorne, 1977). Thus, the continuous range of possible frond lengths was divided into intervals with all the fronds falling in a particular interval being treated as if they were at the mid-point of that interval. In order to identify rational intervals for the size-classes, Silverthorne (1977) determined and accepted the average elongation per quarter (about 2.25 cm) which was then used to define the first size-class. Recruitment was defined as the entry of new fronds into this size class, and biomass was considered as the weight of the frond excluding the first 2.25 cm. Through tagging of plants and study of size classes of the population, loss rates of the population could be estimated and found to be a function of frond length. With these data it was possible to recalculate loss rates for the various size-classes, evaluate the seasonal variations in loss rate and calculate survival rate for each different frond size. Finally, regeneration and recruitment was estimated experimentally. Data suggested a seasonal pattern of recruitment with increased values in winter and fall. Knowing the dry weight biomass per unit of area and the size-class distribution, Silverthorne (1977) could then calculate the average number of recruits in this species (G. robustum). This approximation probably could be used elsewhere in populations of these algal species.
Hypothesis and data related to the increased abundance of tetrasporangial thalli over sexual plants have been reviewed in Section 3.1
It is often impossible to distinguish individuals of Gelidium, therefore density measurements are infrequently used in ecological studies of these species.
No data exist on mortality rates of natural populations of the economically important species of Gelidium in Chile. As discussed in the previous section, in the Californian population of G. robustum the loss rate of the population (=LR) was a function of frond length (L) under the expression LR = 0.00307L (Silverthorne, 1977).
Mortality factors known for these and other populations of Gelidium are discussed in Section 5.2, below.
5.1 Standing stock values of wild resources
5.2 Factors affecting productivity
5.3 Possibilities of genetic improvement
5.4 Relative contribution of sexual reproduction and vegetative regeneration to economic harvesting
5.5 Possibilities of improvement by environmental enhancement
Since the species of Gelidium and Pterocladia are often difficult to distinguish under field conditions, standing stock values reported in the literature may include mixtures of these two genera. Indeed, in some areas such as Japan, the materials identified under the name of Gelidium also might include species of Beckerella, Suhria and Yatabella. Those from Indonesia perhaps include Gelidiella acerosa. Annual production of Gelidiaceae ranges (Table 1) between a minimum of 15,000 and a maximum of 19,000 dry tons per year. The production from wild stocks throughout Chile is just a minor part of this World Market.
The standing stock values normally found in commercial beds of Gelidium vary widely from a few hundred grams to a maximum of 1.5 Kg m-2 In Japan, the fishing fields are classified as excellent if the standing stock is above 1.5 Kg m-2 good if the stock is between 1.0 and 1.5 Kg m-2, common or normal if the biomass of Gelidium is between 0.5 and 1.0 Kg m-2 and bad if the value is less than 0.5 Kg m-2 (Okasaki, 1971). Detailed standing stock measurements are lacking for commercial beds of Gelidium in Chile. Ecological studies (Montalva and Santelices, 1981; Santelices, Montalva & Oliger 1981) have reported stock values of about 0.5 Kg m-2 for Gelidium chilense and 0.9-1.0 Kg m-2 for G. lingulatum. The extremely wave exposed habitats occupied by G. rex together with its clumpy distribution has prevented accurate stock measurements of that species.
TABLE 1. Annual crops of Gelidium and Pterocladia harvested in different area
|
Place |
Fishing Area N° |
Metric Tons (dry) |
Harvesting method used |
|
Spain |
27 |
4000 - 5500 |
Drift, trawling and diving |
|
Japan |
61 |
3000 - 3300 |
Hand picking, diving |
|
Portugal |
27 |
2500 - 3000 |
Drift, hand picking |
|
R. Corea |
61 |
2000 - 2500 |
Hand picking |
|
Mexico |
77 |
1000 - 1500 |
Diving |
|
Morocco |
34 |
1000 - 1500 |
Hand picking, drift |
|
Indonesia |
71 |
400 - 500 |
Hand picking |
|
France |
27 |
300 - 400 |
Drift |
|
U.S.A. |
77 |
150 - 200 |
Diving, hand picking |
|
Chile |
87 |
100 - 150 |
Hand picking |
|
P.R. China |
61 |
100 - 150 |
Hand picking |
|
Corea DPR |
61 |
80 - 100 |
Hand picking |
|
New Zealand |
81 |
50 - 100 |
Hand picking |
|
Formosa |
61 |
50 - 60 |
Hand picking |
|
Total |
|
14,730 - 18,960 |
|
5.2.1 Wild resources
Section 2.3 reviewed the effects of various ecological factors on the growth and production of these Gelidium species. The following factors seemingly affect commercial beds in Chile, as elsewhere, but in general the ecological data to establish quantitative relationships are still lacking.
a) Currents: It is widely recognized that the temperature regime and the nutrient contents of some bodies of water could be important determining distribution and production of species. The general occurrence of upwelling areas along most of the coast of northern and central Chile is suspected to have some effect on the high production rates of these seaweed populations.b) Extreme low tides: This represents a widespread detrimental interaction of factors significantly reducing intertidal stocks. In central Chile there is a significant biomass reduction of Gelidium lingulatum in the months with extreme low tides during clear daylight hours (Montalva and Santelices, 1981).
c) Water movement: Intense water movement has been observed to extensively destroy wild crops of Gelidium robustum in Baja California, G. sesquipedale in Spain, Pterocladia lucida in New Zealand and P. capillacea in the Azores, New Zealand and Alexandria (see Santelices, 1974 for a review). This effect has not been observed in the normally wave exposed populations of Gelidium along Chile.
d) Grazing: Grazing by invertebrates and fishes is also expected to cause mortality at least of erect axes in commercial beds of Gelidium (Santelices, 1974). In Chile pertinent data quantifying the phenomenon are lacking although it is known that the species of Gelidium are common food items of sea urchins and some herbivorous molluscs (Santelices et al., 1983; Santelices and Correa, 1985). Field studies have experimentally shown that intense grazing by the sea urchin Tetrapygus niger could prevent the establishment and cover increase of Gelidium chilense (Ojeda and Santelices, 1984).
e) Competition: The interference effects between Gelidium chilense and G. lingulatum and between G. chilense and Lessonia nigrescens have been discussed in Section 2.3. These studies justify the suggestion that once established the populations of Gelidium are quite resistant to invasions by other algal species. This is probably due to Gelidium having creeping axes which, especially on substrata with a calcareous crusty can survive and produce new erect fronds after harvesting or grazing. In the rocky intertidal habitats of Central Chile, Codium dimorphum is one of the few species able to overgrow the plants of Gelidium chilense (Santelices, Montalva & Oliger 1981).
f) Epiphytes and parasites: There is no quantitative information for these, or for other species of Gelidium, on the effects that the organisms living on or inside their thalli might have on their productivity. This is in spite of the general observation, for example, that Bryozoa are common epiphytes on Gelidium rex.
g) Harvesting practices: Careless harvesting practices can have serious and long-lasting effects on the productivity of Gelidium. Cutting of erect axes always has resulted in less destruction and faster regrowth of the various species than scraping of the substratum (see Santelices, 1974 for a review). Scraping of the substratum normally destroys the creeping axes allowing for the invasion of other algal species. In central Chile, a mixed stand of Gelidium chilense and G. filicinum could recover in 48 months only 45% of the 100% previously occupied rocky surface when removed by scraping of the rocks (Santelices, Oliger & Montalva 1981).
5.2.2 Cultured stocks
Massive cultivation of Gelidium still is at the experimental stage with but a few laboratory and field attempts having been performed in different areas. Three basic types of culture have been attempted.
Field cultivation has been initiated either from spores or from vegetative tissues. Spore cultivation of Gelidium amansii has been successful in Japan (Suto, 1974). However, the spores take about two years to grow and reach harvestable size. More recently, Correa et al. (1985) were able to define the optimal conditions for increased sporeling growth of G. chilense and G. lingulatum but they have not entered the stage of field cultivation.
Field cultivation of vegetative branches also has been completed in Japan (Suto, 1974). However, the economic cost of the plants used as the seed and the cost of the labour force needed for setting the seed plants to the ropes was so expensive that the whole operation left little for profit. This same type of field culture has been successful in growing Gelidium rex in intertidal channels and rapids in central Chile and daily growth rates of 2.5 to 3% have been obtained.
The attempts to grow these species under free-floating conditions represent an alternative approach. The first such attempt were performed with Hawaiian populations of Pterocladia (Santelices, 1976) and, more recently, species of Gelidium from India and Norway have been maintained in free-floating conditions with growth rates up to 6.5% daily. This type of cultivation has been initiated with the three Chilean species of Gelidium. Gelidium chilense was the species with fastest growth, a doubling time of about 30 days. The capacity of these algae to grow free floating is related to their ability to adopt a globular habit, devoid of holdfasts and with production of a profusion of radially-oriented branches. In G. chilense the thalli become globose after 28 days. Radially branching thalli of G. ligulatum resulted from proliferations appearing on the attachment parts of the thalli while G. rex did not show any growth or any modification of its morphology at all (Santelices, Oliger & Montalva 1981).
No attempts seem to have been made to genetically improve the commercial strains of Gelidium.
As commented upon in several sections of this report, the commercial harvests of the three species of Gelidium are based on vegetative regeneration and growth after cutting of the erect axes.
No attempt has been reported to improve production of the Chilean beds of Gelidium through environmental enhancement. In Japan, management of the beds includes regularly adding nitrate and phosphate and expansion of the beds by setting stones in areas of potential growth but otherwise limited by substratum availability.
6.1 Annual cycle of operations
6.2 Manpower productivity
6.3 Alternate employment
All the species of Gelidium presently harvested from Chile are gathered from wild beds either by hand picking in intertidal fields or by snorkel collecting in shallow waters. Since all three species of Gelidium occur in habitats exposed to strong water movement and since storminess along the Chilean coast is seasonal, a naturally closed season probably exists in most areas. However, there is no legal enforcement or regulation restricting access to the Gelidium beds of Chile at any time of the year. Such regulations do exist for other economically important Chilean seaweeds such as Gracilaria.
The harvesting operations of species of Gelidium in Chile are so simple that no one has described manpower productivity. In Japan, Gelidium gathering through swimming and diving in shallow waters yields 14-16 Kg day-1 per fisherman (Yamada, 1976). In Japan two other collecting methods are used. Hand picking of seaweed at depths of up to 15 m after diving from a boat yields 40-75 Kg day-1 per diver (dry matter) while working on a boat and harvesting using woody frames with bamboo teeth can produce 60-115 Kg day-1 per man (Cuyvers, 1978).
Hand picking of Gelidium in Chile is just a part-time activity for most fishermen involved in the operation. During other times these fishermen work gathering other types of seaweeds or various types of shellfish.
The commonest and simplest equipment used in harvesting Gelidium in Chile is a float with a net hanging in it in which the collector puts the hand picked thalli. Knives and iron spatulas are sometimes used to help in the plant's removal. In such a simple operation on one has ever evaluated the efficiencies of the tools used, the percentages of the crop left in the field or the manpower requirements.
8.1 Management of seaweed resources
8.2 Regulation of seaweeds
The Subsecretaria de Pesca, a part of the Ministerio de Economia, Fomento y Reconstruccion is the national body concerned with the management, development and conservation of marine renewable resources, including the seaweeds. The Servicio Nacional de Pesca (National Fisheries Service), one of the Divisions of the Subsecretaria de Pesca is the national body executing the management and exploitation policies. These services are performed by eleven Regional Fisheries Offices each located in one of the 12 Geographic Regions in which the country is divided.
The specialists of the Subsecretaria de Pesca maintain a flexible relation with fishermen associations. Decisions on exploitation policies are normally made after technical studies performed by experts from the Universities, private consulting companies or from the Instituto de Fomento Pesquero (equivalent to a National Fisheries Institute). Problems to be solved arise either from field visits of experts from Subsecretaria de Pesca, from documents produced by the local scientific and technological community or from the fishermen's associations and cooperatives.
The general regulations governing the harvesting and culture of seaweeds are contained in the Decreto 175 issued on March 24th, 1980. In synthesis, any enterprise, individual or association intending to either harvest or culture seaweeds has to produce a technical proposal which is evaluated by the experts in the corresponding Departments of the National Fisheries Service. They submit their technical evaluations to Subsecretaria de Pesca which makes a decision regarding authorizing the given activity. In the case of leasing of a nearshore or intertidal area, the Subsecretaria de Marina (Navy Under-secretariat) would authorize the leasing only after a positive report from Subsecretaria de Pesca.
At present, there is no special legislation governing the culture and harvesting of seaweeds in Chile for any genera, except Gracilaria. Harvesting of Gracilaria spp. is specifically regulated by a different legal body (Decreto 136 of July 2nd, 1983). Therefore, the only legal bodies regulating harvesting and culture of Gelidium beds in Chile are contained in Decreto 175 referred to above.
9.1 Chemical and nutritional content
9.2, 9.3 & 9.4 Human food, animal fodder and manure
9.5 Industrial products and processes
According to Zaneveld (1955), various species of Gelidium analyzed by Matsui (1916) yielded, on a dry weight basis, 2.01% nitrogen, 12.5% crude protein, 23.7% galactan, 2.03% pentosan, 23.2% reducing sugar; 0.93% methyl pentosan, 17.89% fiber, 0.52% magnesium, 0.28% lime and 4.23% ash. Later studies on chemical composition of other species of Gelidium have reported high vitamin B12 content (Tsuda et al., 1958; Guven et al., 1979b; Guven and Guler, 1979a), cholesterol and a series of sterols (Tsuda et al., 1958; Fattorusso et al., 1975; Chardon-Loriaus et al., 1976), essential oils with antibacterial and antifungal activities (Guven and Guler, 1979b; Ma and Tai, 1984), proteins with lipolytic, hypoglycemic and anticoagulant activities (Guven and Guler, 1979b) and lipid soluble extracts with anti-inflamatory properties (Baker, 1984). No equivalent study has been performed with the Chilean species of Gelidium.
Human consumption of Gelidium is restricted mainly to G. divaricatum in China and to G. amansii in Japan, Indonesia, China, Borneo and The Celebes Tzaneveld, 1955, 1959; Johnston, 1966; Levring et al., 1969). Nowhere are the species used as animal fodder or manure. In Chile., all the harvested crops are exported as raw materials for agar production.
Species of Gelidium are among the most important agarophytes in the world (Santelices, 1974; Santelices and Stewart, 1985). About 35 species are harvested in various areas contributing to 40-50% of the world's annual exploitation of agarophytes, estimated at 39,000 tons of dry matter (Whyte and Englar, 1981).
The agar content in the species of Gelidium varies with species (Table 2), season, location and environment. Commercially, 17-25% yield from agarophytes is considered normal (Whyte and Englar, 1981). However, agar concentrations found in several Gelidium species can be far above this (Table 2). Among the Chilean species, Gelidium chilense produces the highest agar yield while G. lingulatum yields the least gel (20%). Gelidium rex yields an intermediate amount of gel but it produces the strongest gel (Santelices, Oliger & Montalva 1981). It should be noticed that Gelidium lingulatum has shown significant differences in viscosity and gel strength among karyologically different generations with the tetrasporangial thalli having higher gel strength values (Santelices, Oliger & Montalva 1981).
TABLE 2. Agar content of several species of Gelidium on a dry weight basis
|
Species |
Locality |
Fishing Area N° |
Amount of Agar |
Reference |
|
Gelidium amansii |
Japan |
61 |
25 to 30% |
Levring et al., 1969 |
|
Gelidium chilense (=filicinum) |
Chile |
87 |
25 to 31% |
Santelices et al., 1981a |
|
Gelidium latifolium |
Java |
71 |
25 to 35% |
Levring et al., 1969 |
|
Gelidium lingulatum |
Chile |
87 |
20 to 24% |
Santelices et al., 1981a |
|
Gelidium micropterum |
India |
51 |
43% |
Levring et al., 1969 |
|
Gelidium pusillum |
Philippines |
71 |
41% |
De León &. Domantay, 1974 |
|
India |
51 |
50% |
Kaliaperumal & Umamaheswara Rao, 1981 |
|
|
Gelidium purpurascens |
California, USA |
77 |
25.4% |
Whyte & Englar, 1981 |
|
Gelidium rex |
Chile |
87 |
27% |
Santelices et al., 1981a |
|
Gelidium robustum (=carti lagineum) |
California, USA |
77 |
40 to 45% |
Barilotti & SiIverthorne, 1972 |
|
Gelidium sesquipedale |
Portugal |
27 |
24% |
Da Fonseca, 1966 |
|
Gelidium spinolosum |
Morocco |
34 |
33% |
Levring et al., 1969 |
|
Gelidium sp. |
Sri Lanka |
51 |
21 to 40% |
Arumugam et al., 1981 |
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