How does commercial fishing affect sharks?
Endangered species: rays and sharks in German seas
The study "Endangerment and protection of sharks and rays in the German marine areas of the North and Baltic Seas" was carried out by researchers from the Center for Natural History at the University of Hamburg on behalf of the Federal Agency for Nature Conservation (BfN). The study from 2017 provides for the first time comprehensive information about the occurrence and endangerment of cartilaginous fish in the German seas. The fish group includes sharks and rays, as well as chimeras - also known as sea cats.
The results of the study show that only one species of cartilaginous fish is currently not at risk. The others are extinct or lost or are in great danger or endangered.
Comprehensive study based on historical and current data
For the study, the research team at the University of Hamburg collected and analyzed historical data from 1625 to 1960 and current data from 1961 to 2015 on the occurrence of cartilaginous fish species in the North and Baltic Seas. For example, the holdings of museum collections in Germany and other countries were included. To this end, various natural history museums provided the research team with information on cartilage fish finds, as well as information on the location and date of discovery.
Precise information on the location and date of discovery was important so that the data could be geo-referenced and transferred to map material. On this basis, the occurrence of the cartilaginous fish species and their development could be shown.
The study was also based on national and international surveys from research and commercial fisheries. These surveys include, for example, regular surveys of certain marine areas by research vessels. The International Council for the Exploration of the Sea (ICES) regularly provides extensive data based, among other things, on trawl surveys.
Data from commercial fisheries were also included in the study. These come from employees of research institutes who ride on randomly selected commercial cutters and analyze the catches and discards. Discards occur because, in commercial fishing, species are often "caught" that unintentionally end up in fishing nets, so-called "non-target species". Such bycatch includes, for example, young fish, smaller marine animals such as crabs, starfish or jellyfish, but also larger marine animals such as sharks, marine mammals and sea birds. In most cases, bycatch is thrown overboard, dead or seriously damaged.
In the EU there is a so-called landing obligation that is to be implemented in all EU fisheries by 2019. This prohibits discards and the fish must be brought ashore. This discard ban is a core element of the EU's reformed fisheries policy from 2013. The landing obligation has been in force in the Baltic Sea since 2015 and has been in force in the North Sea since 2017.
Occurrence and endangerment of the cartilaginous fish species
On the basis of this extensive data collection, evidence of a total of 19 species of cartilaginous fish was compiled for the German marine areas of the North and Baltic Seas.
Ten species are classified as established in the German seas. These are species that regularly reproduce in the study area. This also includes species that reproduce outside the observation area, but occur regularly in it. The established types of cartilaginous fish include dog shark, white-spotted dog shark, small-spotted dogfish, dogfish, star rays, cuckoo rays, thorn rays, spotted rays, common stingrays as well as the common skate and its relatives.
In addition, one species of chimera, three rays and five shark species are currently irregularly found in German waters and are therefore not established. This includes, for example, the basking shark, which is more of a migrant.
Of the ten established cartilaginous fish species, only one is not threatened, that is the small spotted dogfish. The common stingray and the common skate have either died out or disappeared in German waters. Nail rays and dogfish are threatened with extinction, dog sharks and star rays are endangered or endangered. Cuckoo rays and spotted rays are extremely rare. Due to insufficient data, no risk analysis could be carried out for the white-spotted smooth shark.
Threats to cartilaginous fish species: direct and indirect effects of fishing
In the study, various causes for the endangerment of the cartilaginous fish species are named. Above all, this includes the indirect effects of fishing, which endangers all established cartilaginous fish species in the German marine areas - with the exception of the small-spotted cat shark, which is not at risk. The animals are not caught in a targeted manner, they are caught unintentionally. However, most of the animals do not survive being thrown back into the water, as it damages the catching procedure too much.
Trawling in particular leads to high bycatch rates, including invertebrates such as crabs, starfish and sea urchins. These in turn are an important food source for individual cartilaginous fish species. In addition, trawling has seriously affected the seabed. Individual areas in the southern North Sea are fished with bottom trawls up to ten times a year. This has contributed to the change in the marine community in these areas.
In addition to these indirect effects from fishing, targeted fishing also poses a threat to individual cartilaginous fish species. For example, dogfish and smooth thai can be fished. Basking sharks are not allowed to be caught according to international agreements. Direct, targeted fishing also contributed to the endangerment of dogfish, in particular, until the European Union (EU) reduced the statutory maximum catches to zero in 2010. This rule applies to EU waters as well as to EU ships in international waters. But initially there was still a quoted by-catch permit, which was withdrawn in 2011. Since then, landings of the dogfish have been prohibited, so that all accidentally caught specimens must be carefully and immediately returned to the sea. However, in addition to the EU, the spiny dogfish in the north-east Atlantic is also managed by Norway, Iceland and the Faroe Islands, each with separate rules. For example, targeted fishing for dogfish is prohibited in Norway. However, by-catches have to be landed, i.e. brought ashore.
Changes in habitat and consequences of climate change
In addition to fishing, habitat changes due to human intervention are also a problem for the cartilaginous fish species. The interventions include, for example, the construction of offshore wind turbines, the laying of submarine cables and pipelines or dredging work to deepen or maintain fairways, for example. However, not all changes to the habitat necessarily have a negative impact on all species.
In particular, submarine cables that transport electricity from offshore wind turbines to land could have negative effects on the cartilaginous fish. Because the cables generate electric fields, albeit weak ones. Cartilaginous fish have special sensory cells, so-called electroreceptors, with which they can perceive electrical fields and field changes. It could be that the electric fields of the submarine cables affect the cartilaginous fish, for example by changing their original migration routes. It could also be that the animals can no longer find food organisms. Because they use their electroreceptors to perceive muscle contractions in crustaceans, for example. However, more research is needed to gain a better understanding of the effects of electromagnetic fields around submarine cables.
Climate change also has an impact on the cartilaginous fish species. These include, for example, changes in water temperatures: An increase in temperature worsens the living conditions of cold-loving species, such as the star ray. The increase in storms, in turn, can lead to higher embryo mortality in egg-laying shark and ray species, as the egg capsules can increasingly be washed ashore.
Species protection secures our existence
The protection of cartilaginous fish species and thus species protection as a whole are of central importance for biological diversity. This includes the diversity of species and habitats as well as the genetic diversity within the individual animal and plant species. This is not just about maintaining the intrinsic value of nature, but also about the basis of existence of all species, including humans. With the loss of biodiversity, we deprive ourselves and future generations of important development opportunities.
But the total number of species is falling dramatically with the rapidly increasing human population. Every year around a thousand times more species die out worldwide than would be the case under natural circumstances. 35 percent of the native animal species in Germany and 26 percent of the plant species are endangered.
The critically endangered or endangered cartilaginous fish are also subject to species protection. They include a whole range of species that are at the top of the food web. They are known as top predators or "top predators". They eat organisms from levels below in the food web. When the number of cartilaginous fish is reduced, this leads to imbalances in the food web. In addition, top predators mainly eat prey organisms that are weakened and / or sick. In doing so, they contribute to natural selection. A loss of the cartilaginous fish species would have negative effects on the marine ecosystem as a whole. Because species are always a basic unit of biotopes, ecosystems and landscapes.
In addition, Germany is obliged to protect species due to legal requirements, EU law and international agreements. The Basic Law provides in Article 20a that the state protects the natural foundations of life, also in responsibility for future generations.
Which protective measures are possible?
In order to protect the cartilaginous fish species in the North and Baltic Seas, the research team at the University of Hamburg calls for the creation of special marine protected areas. The potential of the marine Natura 2000 areas could be used for such retreat areas.
Natura 2000 is an EU-wide network of protected areas for the conservation of endangered or typical habitats and species. These protected areas are designated on the basis of the European Birds Directive from 1979 and the Fauna-Flora-Habitat Directive from 1992. With currently over 27,000 protected areas on almost 20 percent of the area of the EU, Natura 2000 is the largest cross-border, coordinated network of protected areas worldwide. It not only includes land on land, but also protects habitats and species in the sea.
In Germany, the federal states are responsible for implementing Natura 2000 on land and in the territorial waters - i.e. within the twelve nautical mile zone. The federal government is responsible for the area of the Exclusive Economic Zone, which adjoins the twelve nautical mile zone and extends to international waters beyond the 200 nautical mile zone. Cross-border regulations are required for international waters.
In 2004, a total of ten Natura 2000 areas were reported to the EU in the German Exclusive Economic Zone of the North and Baltic Seas. Two of the areas for the protection of sea birds have been designated as national nature reserves since 2005. The other eight areas were recognized by the EU as sites of Community importance in 2008, for example the Dogger Bank. The statutory ordinances and management plans for these areas are currently being drawn up in Germany.
For these Natura 2000 areas, scientists are calling for measures to regulate commercial fishing - so-called fisheries management. This includes, for example, the complete exclusion of fishing in certain areas, i.e. zones without any fishing at all. Likewise the reduction of the fishing effort and the adaptation of the fishing gear. Fishing gear that comes into contact with the bottom, such as bottom trawls, should only be used to a limited extent or not at all. Pilot studies show that the use of ecosystem-compatible fishing gear is also possible as an alternative to the bycatch-intensive fishing methods.
The Federal Agency for Nature Conservation has worked with the Fisheries Research Institute (Thünen Institute) to develop a fishery management system with spatial and temporal restrictions in marine protected areas. These measures aim to limit the negative effects of fishing on protected habitats and species. These measures can also have a positive effect on the protection of feeding and spawning grounds for various types of cartilaginous fish.
In addition to fisheries management, it is also crucial to avoid habitat changes in the protected areas due to other human activities, for example by avoiding the removal of sand and gravel.
It takes national and international rain
An international network of protected areas in the North Sea region could help with the reintroduction or recovery of the extinct or endangered species of sharks and rays. But such protected areas in the North Sea need not only a German, but an international set of rules. In order for species protection measures to be effective, cross-border concepts are required. One of the possible managed protected areas is, for example, the aforementioned Dogger Bank, to which Germany, the Netherlands and Great Britain have also registered Natura 2000 areas.
In addition, consumers can also contribute to the protection of cartilaginous fish by avoiding products made from cartilaginous fish. These include, for example, the Schillerlocken, a product of the dogfish. Consumers can turn to fish guides when it comes to buying fish. The environmental organization Greenpeace, for example, offers such a guide.
Center for Natural History at the University of Hamburg: Study on the endangerment and protection of sharks and rays in the German marine areas of the North and Baltic Seas
Federal Agency for Nature Conservation: Fisheries management in marine protected areas
Federal Agency for Nature Conservation: Effects of bottom trawling
Federal Environment Ministry: Natura 2000
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