Resource variables proposed to monitor the harvest of Lessonia nigrescens complex.
Abstract
Chilean fishery of brown algae includes species belonging to the genus Lessonia, Durvillaea, and Macrocystis, which can be found along the coast, ranging latitudes from 18° to 55°S. The exploitation of these seaweeds is done mainly in the Northern coast because the environmental conditions of this region decrease initial production costs. Brown algae are exploited from natural populations and exported to international markets as row material, source of alginates, widely utilized in diverse manufacturing processes and industries. International demand for Chilean kelps has produced sustained increase in harvest during the last decade, reaching more than 390,000 dry tons/year. This chapter approaches the most relevant aspects of the brown seaweed fishery in Chile which covers a wide range of the Southeast Pacific coast, considering the number of commercial species, its abundance and distribution, knowledge achieved on their ecology and biology regarding management, and conservation of these resources, and finally, provides tools for stakeholders and policy makers directed to sustainable management of natural kelp beds occurring in the cold temperate seas.
Keywords
- Brown algae
- kelp
- fishery
- coastal environment
- management
1. Introduction
Chile, a narrow and long country with over 4500 km of continental coastline, has an ancient tradition in the use of sea resources. Numerous algae, shellfish, and fish species have been incorporated in the diet and every day habits of his inhabitants, since prehistoric times. The astonishing evidence found at the archaeological site Monte Verde, dated 12,500 years BP and located near Puerto Montt (41°S), provides evidence of Pre-Clovis human settlement in South America, and exhibits ancient use of macroalgae, probably as food and for medicinal purposes [1, 2]. The diet of coastal human communities incorporated brown and red algae as significant components along the last 500 years, especially in those coastal populations situated South beyond 30°S [3].
As sources for alginates production, brown algae in Chile are exploited from natural populations and exported to world markets as row and dried commodity for alginates extraction [4, 5]. The local national gel industry, as well as invertebrate aquaculture production, utilizes only a minor fraction of the annual harvest [6]. During the last decade, a sustained increase of harvesting has been taking place, because of the international demand for Chilean kelp; production has reached more than 390,000 dry tons associated with an economic return of more than US$ 90 million [5, 7]. Chilean brown algae of economic importance belong to genus
In Chile, the harvest of brown algae is also matter of social relevancy since more than 15,000 people depend more or less directly on the exploitation and collection of this marine resource [9]. As established by local law, only authorized and registered artisanal fisherman are allowed to harvest such kelp [6]; however, enforcement measures and control are difficult to put into effect because of the topography of coastal territory where these natural populations of kelp occur, but also due to their extension and accessibility [10]. From the point of view of their ecological role, kelps have been defined as engineer species in the coastal marine ecosystems; they are key species which participate maintaining and preserving foci of high biological and genetic diversity [11, 12]. Also, these species are sensitive to disturbances from both natural and/or anthropogenic origin [13, 12].
2. Species in the fishery
Geographic distribution and occurrence of commercial brown seaweed are associated with high-energy environments in the Southeast Pacific (Figure 1).
Chilean kelp species commercially exploited are as follows:
3. Biological and ecological aspects
Studies on the distribution and abundance of Chilean commercial brown seaweed were scarce and locally restricted until the end of 2000 [21–29, 30, 31]. Other than this, the use of non-comparable methodologies in the few studies carried out, which approached biomass stocks information, did not allow extrapolation and inter-annual comparisons of the available total biomass. Similar situation occurred in relation to distribution studies of the involved species, both in temporal and spatial gradients [4]. Harmonization of methods or collection of information, as well as systematization of them, is essential aspects of the population ecology of commercial species, in order to propose adequate regulations and policies that guarantee a sustainable management of these resources.
One of the few extensive and intensive evaluations of biomass distribution of
In contrast to the lack of ecological information used to determine fishery regulations, several studies arise since the middle 1980s approaching different aspects of kelp knowledge, such as biology and population ecology [12, 13, 17, 32, 33], genetics and taxonomy [18–20, 34], enhancement and cultivation [35–38], new and novel uses for their natural by products, for medical nanotechnology, for example (see [39–41]).
Because of
Exploited and unexploited species belonging to
4. Collection, harvest, and landings
Largely and until year 2000, the whole brown algae fishery in Chile was based on the collection of natural mortality kelp from coastal populations. A sudden and significant increase of its demand, other than as raw material for alginate source, also as food source for cultivated abalones introduced in Chile in the last 16 years, triggered the harvest of kelp species. Since then, the Chilean brown seaweed fishery becomes an extractive fishery in which converge four main factors: (1) still the international market request for alginic acid source; (2) use for feeding the emergent local farming of several kelp-consuming organisms under controlled conditions; (3) the switch of fishers toward the harvest of commercial brown seaweeds as consequence of the collapse of other benthic fisheries, and (4) the strong impact on local economy produced by the international fluctuation of the price of copper. This metal constitutes the Chilean main resource, representing more than 60% of the internal gross product (PIB, as its acronym in Spanish); it provides direct and/or indirect jobs for thousands of people in the country, being Chile the first copper producer around the world. Local economy is extremely sensitive to fluctuations of international cooper price, and the fall (currently crush) of it provokes significant unemployment, particularly of non-specialized workforce; as one of its primary consequences, unemployed people are forced to migrate to coastal areas where they can develop subsistence economy based on precarious jobs represented by the collection and harvesting of brown seaweeds [9, 6].
During the last 35 years in Chile brown algae, landings have fluctuated between 40,000 and 390,000 tons/year, showing sustained increase since 2000 (Figure 2);
The significant rise of kelp demand, as commodity source of alginic acid around the world during the last years, explains the increase of kelp extraction. A smaller fraction of this increment is consequence of the yield reduction of kelp used for milling, because of higher humidity contents of lately processed plants if compared with those from previous years [7, 50]. From a different perspective, during 1997–1998 when a severe ENSO event occurred, Chilean exports of brown algae showed a considerable peak, probably related to significant mortalities generated by this large scale oceanographic event. The warming of the ocean surface, simultaneously to decreasing of nutrients concentrations, both associated with “El Niño,” has strong impact over kelp populations and thousands of dead plants are cast ashore by waves which end collected by fishermen [16, 23, 60].
Since 2005, the abalone cultivation industry exhibits a remarkable and sustained growth, especially in Northern Chile; this commercial activity consumes close to 4800 tons of fresh alga/year, mainly
5. Management
Chilean authorities have implemented a management and conservation strategy program for economically important brown algae, considering its economic, social, and ecological importance, and also the significant increase of kelp harvest. The expectative of this program is focused on surveillance of available and harvestable biomass, evaluation of strength of harvesting (Capture per Union Effort-CPUE), and characterization of the productive chain based on these primary producers. As a result of this strategy, carried on since 2010, plus several years of kelp knowledge achieved, recommendations have been established for the management of kelp sustainability. The premise is “
The main practical recommendations of the program for the sustainability of brown seaweeds are focused on selective harvesting of adult sporophytes and maintenance of a permanent stock of individuals able to reproduce, recruitment facilitation, decrease of grazing by benthic invertebrates, and permitting the sustainability of kelps and the conservation of its associated biodiversity [6, 5, 56, 62]. Considering all aspects mentioned, the following bio-ecological recommendations must be applied to kelp beds subjected to significant, frequent, and intense harvesting: (1) to harvest the whole plant, including the holdfast. (2) To harvest plants with a basal diameter larger than 20 cm. (3) To harvest one out of every three plants, with preference for the biggest specimens, thereby thinning the population. (4) For the particular case of
According to administration regime (Conservation Strategy) assigned by competent authority to natural populations, the density of both adult plants and juvenile recruitment of
The density of adult plants is greatest in populations inside MPA in contrast to those inside OAA (Figure 3). As previously exposed in MAEBR, the seasonal harvest of
In MPA,
The size structure of
After 25 years of observation and assessment of
As last recommendations, it will be necessary to make significant progress in areas such as: (a) perfection of the capacities of commercial management by using social capital, (b) optimization of control mechanisms and enforcement considering the idiosyncrasy of Chilean artisanal fishermen, (c) improvement of information flow between and among the different actors in the productive chain and the authorities, and (d) establishment of controlled extraction of brown algae by using management plans from territorial perspective.
A participative, adaptive, and multidisciplinary management plan requires ecological indicators that permanently monitor administrative measures agreed upon by the direct users of
Resource variable |
Description | Time regime |
Decision policy |
Verification source |
Additional requirements |
Investment items |
---|---|---|---|---|---|---|
Landing (kg) |
Fishing/ harvesting area |
Permanent (daily) |
Once fishing quota is reached, stop the harvest |
Artisanal fishing |
Implemen tation of an electronic registration system for harvest/ landing |
Implemen tation, maintenance of electronic equipment. Training |
Capture per unit effort (CPUE) |
Capture per unit effort (kg/h/ fisherman) per bed or area. Fishing gear: “barreta” |
Permanent (Monthly) |
Once CPUE >150 kg/fisherman/h (Fishing ban, extraction area rotation, change fishing gear) |
Scientific survey, Landing register, Fishermen statistics |
Implemen tation of CPUE registration system by area |
Monitors for recording landing information. Training |
Minimum legal size of capture (MLS) |
Morpholo gical variable: holdfast diameter. MLS 20 cm |
Permanent (seasonal) |
Once MLS of holdfast diameter ≤ 20 cm. (Change harvesting area, fishing ban) |
Scientific survey, landing register, fishermen statistics |
Implemen tation of a registration system of MLS by area |
Monitors for recording landing information. Training |
The effect of harvesting in OAA has been explained by the absence of precautionary management measures in a scenario of high demand for biomass [9, 14, 44, 46]. Thus, management based on the ecosystem approach requires ecological indicators sensitive to harvesting pressure, which allow establishment of decision criteria that are easy to observe, communicate, and measure by both scientific observers and artisanal fishermen [49]. Demographic attributes, such as density of adult plants, biomass per unit of area, recruitment, and size structure all constitute indicators that satisfy these characteristics, are easy to obtain and can be evaluated along spatial and temporal gradients (Table 2) [49].
Demographic variable | Description | Time period |
Decision policy (criteria) |
Verification source |
Additional requirements |
Investment items |
||
---|---|---|---|---|---|---|---|---|
Harvest | No-harvest | |||||||
Density of adult plants >20 cm holdfast diameter |
Number of plants per m2 |
Permanent (seasonal) |
Once adult plant density ≥2.0 plants m2 |
Once adult plant density ≥1.5 plants m2 |
Landing from fishermen, Scientific survey |
Implementation of a registration system by harvesting area, zone or Region |
Training for registration system. Scientific survey |
|
Biomass | kg/m2 | Once biomass ≥25 kg m2 |
Once biomass <20 kg/m2 |
|||||
Recruitment | Number of recruits m2 ≤1 cm holdfast diameter |
Once number of recruits ≤5 plants/m2 |
Once number of recruits > 40 plants/m2 | |||||
Size structure of populations in natural beds |
Population size structure using holdfast diameter as morphological indicators |
Once standing crop ≥30% standing stock |
Once standing crop <20% standing stock |
Based on demographic indicators, the rule establishes that the harvest in OAA should begin when the abundance and biomass of a population per unit of area is close to biomass or demographic levels detected in an un-intervened population (e.g., MPA): There is a minimal density of recruits, the portion of adult plants must be above 40% of the total population, and the percentage of remaining adult plants in the area should be enough to generate post-harvest recruitment (Table 2). Afterward, once the population reaches levels of abundance and biomass per unit of area similar to those found in the population under intense harvesting pressure (e.g., OAA), its sustainability will depend on following elements: (1) stability of recruitment frequency, (2) maintenance of a stock of reproductive individuals, and (3) stability of harvesting frequency. Once these indicators exceed the harvesting period should end and should be followed by a recess period (ban or quotas), until adequate pre-harvest values would be reached (Table 2). Thus, the installation of a permanent monitoring program of the populations of
6. Concluding remarks
The landings of brown seaweeds in Chile [61] reach 390,000 wet tons/year being the world's largest landings from natural populations. This fishery is managed under the concept of “good practices,” based on biological and ecological knowledge of the species [6, 12, 14, 23, 25, 32, 48, 57–59]. Most of the brown macroalgae are known as foundational species of marine ecosystems [12]; they constitute the basis of coastal food webs [14, 26, 60, 62], contribute significantly to the total biomass of the ecosystem [23, 32], and are highly connected with all trophic levels [61]; they provide shelter, food, nursery, and breeding areas [23, 32, 6]. Indiscriminate harvest of a foundational species as
Acknowledgments
This synthesis is the result of numerous research projects financed by public and private institutions and with the participation of many co-workers, students, and technicians. I deeply appreciate the support of CONICYT-Chile, FONDECYT, FONDEF-Huam AQ12I0001, and COPRAM-Chile.
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