SISTEMAS DE CONTROL DE LA TRAYECTORIA

While worldwide general marine fisheries landings seem to have reached a plateau in the late 1980’s, elasmobranch catches have been increasing progressively since the 1950’s, with decreases occurring only in the last few years, specifically 2004 and 2005 (Figure 1.1). However, worldwide marine fisheries have shifted in these last decades from catching long lived high trophic level fishes toward catching mainly short lived, low trophic level invertebrates and planktivorous pelagic fish (Pauly et al.,

1998; Pauly and Palomares, 2005). This effect, originally called “fishing down the food web” by Pauly et al. (1998) shows that the marine ecosystems top predators are the first ones to suffer from overfishing, with unsustainable exploitation patterns occurring presently. The fisheries, in order to compensate for the faster declines of these top predators, have to rely increasingly on fish and invertebrates that are of lower trophic levels.

World - Sharks, rays and chimeras

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1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year

Landings (thousands ton)

a)

Figure 1.1. World landings of all marine fishes (a) and sharks, rays and chimeras (b), from 1950 to 2005. Data from FAO FIGIS data collection (FAO, 2007).

Up until the 1980’s, elasmobranch fisheries were generally unimportant, small fisheries, with very little commercial value worldwide. Traditionally, these elasmobranch fisheries of the past were multi-specific fisheries that caught several species of elasmobranchs depending on the region and the season of the year. There was little or no interest in these fisheries, mainly due to their relatively small size and the low commercial value of elasmobranchs. Bonfil (1994) reported that cartilaginous fishes were a minor group which contributed with an average of 0.8% of the total world fishery landings between 1947 and 1985, while bony fishes such as clupeoids, gadoids and scombroids, accounted for 24.6%, 13.9% and 6.5%, respectively. In the last decades however, the declining catches per unit effort (CPUE) and rising prices of traditional food fishes, along with the growing market for shark fins for oriental markets, have made the previously under utilized elasmobranchs increasingly important resources. During the 1980’s, elasmobranch fisheries throughout the world were growing at a rapid pace and by the mid 1990’s, the high value of dry shark fins provided sufficient incentive to harvest sharks, even when the meat was not marketable (Castro et al., 1999).

The history of elasmobranch fisheries worldwide indicates, however, that these resources are usually not sustainable. Most elasmobranch targeted fisheries have been characterized by a “boom and burst” scenario, where an initial rapid increase of the exploitation and catches is followed by a rapid decline in catch rates and eventually a complete collapse of the fishery (Stevens et al., 2000). This situation seems to be particularly common in deep water species, including not only elasmobranchs but also the bony fishes (Haedrich et al., 2001). However, and even though overexploitation and population collapses is the most common scenario in elasmobranch fisheries, Walker (1998) demonstrated that elasmobranch stocks of some species can be

harvested sustainably and provide for stable fisheries when carefully managed. Some species such as the tope shark, Galeorhinus galeus, the sandbar shark, Carcharhinus plumbeus, the great white shark, Carcharodon carcharias and several species of dogfishes (order Squaliformes) have low productivity and cannot withstand high levels of fishing, whereas other species such as the gummy shark, Mustelus antarcticus, the Atlantic sharpnose shark, Rhizoprionodon terraenovae, the bonnethead, Sphyrna tiburo and the blue shark, Prionace glauca have higher productivity and can support higher levels of fishing mortality (Walker, 1998).

A huge problem with many current fisheries that is generally not reflected in landings databases is by-catch and especially discards (Zeller and Pauly, 2005). Most fisheries operating around the world catch elasmobranchs as by-catch and although some species are retained and utilized in some of these fisheries, others are discarded, sometimes after their fins have been removed. The survival of discarded elasmobranchs may vary depending on the species, the type of gear used and the depth where they have been caught, but there is a consensus that trawls, gill nets and purse seines cause high mortalities while longlines may allow for better survival rates (Bonfil, 1994). The by-catches and discards of elasmobranchs in large scale fisheries around the world are large and the associated unreported catches may represent as much as 50% of the total reported elasmobranch catch (Bonfil, 1994; Stevens et al., 2000).

In Portugal, landings of marine fishes from 1950 to 2005 were characterized by a peak during the 1960’s and a smaller peak in the mid 1980’s, but in general have been deceasing (Figure 1.2). Specifically, total Portuguese landings peaked at 560 thousand ton in 1964 and decreased by some 66% down to 188 thousand ton in 2005.

On the other hand, elasmobranch fisheries remained relatively unimportant until 1990,

when substantial increases were reported for a few years, but have decreased sharply since then (Figure 1.2). However, the relative importance of elasmobranch fisheries has been increasing substantially: the elasmobranch landings represented on average 1.0% of all Portuguese marine fish landings between 1950 and 1989 but this value increased in recent years with elasmobranch landings between 1990 to 2005 representing an average of 7.4% of all marine fish landings.

Elasmobranch fisheries in Portugal are not regulated, and thus there are no established minimum landing sizes or maximum catch quota limits for any species.

According to Correia and Smith (2003), current Portuguese elasmobranch landings come mainly from five distinct fisheries, 1) targeted deep-sea elasmobranch longlining, 2) targeted pelagic elasmobranch surface longlining; 3) by-catch of deep water elasmobranchs from deep sea longlining; 4) by-catch of pelagic elasmobranchs from teleost gill-netting, purse seining, and bottom trawling, and 5) by-catch of deep water elasmobranchs from crustacean bottom trawling.

Portugal - All marine fishes

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year

Landings (thousands ton)

Portugal - Sharks, rays and chimeras

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1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year

Landings (thousands ton)

b) a)

Figure 1.2. Portuguese landings of all marine fishes (a) and sharks, rays and chimeras (b), from 1950 to 2005. Data from FAO FIGIS data collection (FAO, 2007).

The Algarve region does not differ much from the national scenario, with records from 1988 to 2005 showing a trend of a general decline in landings in this region. Specifically, landings of elasmobranchs in 1988 in this region peaked at 888 ton and declined by some 38.1% to 550 ton in 2005 (Figure 1.3). On the other hand the commercial value of these resources has been increasing progressively. The average value of elasmobranchs sold at auction in the Algarve increased by 133%

from 1988 (0.81 Euros per Kg) to 2005 (1.90 Euros per Kg) (Figure 1.3).

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Figure 1.3. Landings and average value of elasmobranchs landed in the Algarve region from 1988 to 2005. Data from DGPA (GEPP, 1988; 1989; 1990; 1991; 1992;

1993; DGP, 1994; 1995; 1996; DGPA, 1997a; b; 1999; 2000; 2001; 2002; 2003;

2004; 2005; 2006)

One of the major problems with these large statistical databases is that data is not usually specified down to species level, and there is no way to discriminate between species, with the analysis usually having to be performed at higher taxonomic levels such as genus or even family. Most deep water species are even more problematic, given that due to their low or even null commercial value they are often discarded at sea and there is no way to account for fishing mortality in these landings statistics. That is the case of most catches of lantern sharks worldwide, where due to the small size of most species, specimens are usually discarded. Nonetheless, the FAO databases (FAO, 2007) does have two categories to list lantern sharks: the general “lanternshark NEI” group that refers to Etmopterus spp. and the “velvet belly (ETX)” group that refers specifically to Etmopterus spinax. Up until 1995 no recordings appeared for either of these categories, but from 1995 to 2005 some catches were recorded. Specifically, between those years, there were 953 ton of

Etmopterus spp. landed worldwide, of which 871 ton were recorded in Europe. The 75 ton of E. spinax landed in Europe accounted for the entire catch reported worldwide for this species (Figure 1.4). Portugal does not have records in any of these two categories.

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year

Figure 1.4. Etmopterus spp. (a) and Etmopterus spinax (b) worldwide and European landings from 1995 to 2005. On E. spinax, the world and European landings are the same. Data from FAO FIGIS data collection (FAO, 2007).

The rapid growth in the size and value of elasmobranch fisheries in the last few decades, the alarming increase of elasmobranch by-catch of other fisheries and the fact that we now know that these resources are highly vulnerable to overfishing, has

created a worldwide concern and the management and conservation of these resources is now a clear objective.

In 1999, the FAO developed the International Plan of Action for the Conservation and Management of Sharks (IPOA Sharks) (FAO, 1999). This tool was a voluntary instrument that applied to all States where elasmobranch fisheries take place and that set out guidelines that the implementing States were encouraged and expected to carry out in order to protect and manage these resources. Such measurements included highly general goals such as making sure that elasmobranch catches were sustainable, and other more direct goals such as monitoring elasmobranch catches, encouraging the full use of dead elasmobranch and reporting species specific biological and trade data. So far only a few countries have effectively developed their respective National Plans of Action and even fewer are implementing them, so the progress made is clearly insufficient (Fowler et al., 2004).

On the other hand, the Shark Specialist Group (SSG) of the World Conservation Union (IUCN) has, since 1991 when it was first established, been making a huge effort to assess all elasmobranch species described worldwide, in order to include them in the IUCN Red List of Threatened Species (IUCN, 2006a). This list is widely recognized as the most comprehensive source of information on the global conservation status of plant and animal species and can therefore be used as a tool for measuring and monitoring changes in the status of elasmobranch biodiversity. The assessments presented there are an essential baseline which evaluates the conservation status of individual species, identifies threats affecting them and if necessary, proposes recovery objectives. Up until the end of 2006, 547 chondrichthyan species had been assessed under the IUCN Red List criteria (IUCN, 2001), of which some 20% were listed under one of the threatened categories (IUCN, 2006b).

These IUCN SSG assessments have also been used to advise on the inclusion of elasmobranchs in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The CITES has been playing an important role against over exploitation of wild fauna and flora species by regulating international trade. The species can be listed in one of three different Appendices: Appendix I lists the most threatened species and international trade is entirely prohibited unless exceptional circumstances are demonstrated (e.g. for scientific research); Appendix II lists species where trade may be authorized if it is demonstrated that it will not be detrimental to the survival of the species in the wild and Appendix III list species already regulated by one or some countries and that need cooperation of other countries to prevent unsustainable or illegal exploitation. As a consequence of the assessments that have been carried out by the IUCN SSG, three chondrichthyan species, namely the whale shark, Rhincodon typus, the basking shark, Cetorhinus maximus and the great white shark have already been included in CITES under Appendix II, and two more species namely the piked dogfish and the porbeagle, Lamna nasus, and an entire family (the sawfishes, family Pristidae) have been proposed to be included this year during the 2007 Conference of the Parties (CoP 14) (Fowler et al., 2004; Lack, 2006).