On our table today, there are a lot of ingredients from the ocean. In addition to the traditional local offshore products, there are also many species that have traveled far and wide to come to us:
The cod in the deep-sea cod fort are the yellow-lined narrow cod Gadus chalcogrammus from the North Pacific; the tuna sashimi or canned tuna is the tuna Thunnusspp. or bonito Katsuwonus pelamis from the tropical sea; the French silver cod has nothing to do with France and has nothing to do with the cod, they are the small scaly dog tooth antarctic fish Dissostichus eleginoides from the waters near the Antarctic...
What we often call "silver cod" belongs to the genus Canine Tooth Antarctica of the Antarctic fish family Of the order Perciformes, while the true cod refers to the three species of fish under the cod family Cod. 丨wikimedia
Thanks to the development of fisheries and modern logistics, we can eat these delicious seafood that seem to be very far away from us in geographical distance. But we know very little about how they came to us from the vast sea than we are familiar with their tastes.
Let's start with the tuna we're familiar with.
No.1
Trapped dolphins
In the distant eastern Pacific Ocean, the target species for tuna fishing are the yellowfin tuna Thunnus albacares, the big-eyed tuna T Albacares and.
Bonito belong to the same family as other tuna. Although Chinese name does not carry "tuna", bonito also belongs to the tuna, and its common English name is "skipjack tuna". 丨Wibowo Djatmiko / wikimedia
For tuna, a type of sea swimmer, early people caught them using live bait rod fishing. Although less efficient, rod fishing is more selective for tuna, and fishermen catch almost invariably fat gunfish that resemble cannonballs.
Tuna in clusters in the sea. 丨United Nations Food and Agriculture Organization / Danilo Cedrone
It was not until the 1950s that purse seine fisheries developed with the upgrading of synthetic net technology and vessel power. Some U.S. tuna fishermen have abandoned inefficient rod fishing in favor of purse seine techniques to catch tuna.
The so-called fence is a huge mesh that can stretch for one to two kilometers in length and two meters in height. When schools of fish are spotted, purse-seine vessels tow one end of the net to quickly envelop the school. When the bag of fish is completed, the bottom of the net is also tightened, and the fish is completely destroyed.
Schematic diagram of purse seine fisheries operations. 1. Purse seine boats surround fishing stocks; 3. Floats; 4. Shenzi;4. The bottom of the seine was tightened and subsequently pulled onto the fishing boat. 丨 GoodFishBadFish /Flickr
This gear, called purse seines, greatly improves the efficiency and volume of tuna. But at the same time, it also brings a problem -
In the eastern tropical Pacific, tuna is not always present alone. Sometimes, under the factor of bait, they will appear in pairs with dolphins. Therefore, experienced tuna fishermen often use swarms of dolphins on the surface to locate yellowfin tuna tracks.
At that time, when people were fishing for tuna, they did not deliberately distinguish between dolphins and tuna, and once they found the traces of dolphins and tuna, they used huge purse seines to catch dolphins and tuna back. The catch thus caught naturally consists of tuna and innocent dolphins in the net.
This tuna catch, which contains dolphins, is figuratively known as a dolphin sets.
Spotted proto-dolphins in tuna purse seines. 丨NOAA
This indiscriminate fishing method has led to the death of a large number of dolphins. It is estimated that in the 1960s, more than 100,000 dolphins died each year due to tuna purse seine fishing.
The two most deadly species of dolphins in the Eastern Pacific Tuna Purse Seine Fishery, the spotted proto-dolphin and the Oriental Longnose Proto-Dolphin, have an annual death toll. 丨NOAA
The mass death of dolphins caused by tuna purse seine fishing has caused concern among the American public. This concern partly prompted the United States to pass the Marine Mammal Protection Act (MMPA) in 1972.
Since then, environmental groups have banned the sale of dolphin-containing tuna in the United States by imposing trade restrictions. Faced with such an environment, tuna fishermen have also had to improve their fishing methods to reduce the bycatch rate of dolphins, and actively provide rescue for dolphins that are accidentally caught.
The "Dolphin Safe" logo from the U.S. Department of Commerce. 丨wikimedia
Until recent years, the annual number of dolphin deaths from fishing in the Eastern Pacific ocean has fallen to less than 1,000, a few hundredth of what it was half a century ago.
The problem of tuna and dolphins is a tragedy caused by the irrational use of natural resources by humans, but it still has some positive implications: since then, people have realized the seriousness of the problem of bycatch in fisheries and have begun to pay attention to the problem of bycatch in fisheries worldwide.
No.2 Bycatch: The Shadow of Fisheries
In fisheries, such bycatch is known as Bycatch, Chinese translated as bycatch, mixed catch or by-catch. In its 2005 statistical report, the Food and Agriculture Organization of the United Nations (FAO) defined by-catch as catch of all non-target species of animals.
Although the worldwide concern about bycatch has only emerged in recent decades, the problem of bycatch has a long history and has always been accompanied by fisheries.
People choose the right gear and catch the target catch they want. For example, saury gangtnet (a kind of netting) is mainly used to catch saury, while purse seines are used to catch marine pelagic fish with strong clusters such as tuna and mackerel.
Netting refers to a type of net that is pre-laid horizontally in the water, waiting, luring or driving the fishing object to the top of the net, and then lifting the net to the surface of the water to catch the catch. The working principle of the saury gang net: the net (gang net) set on both sides of the hull is pre-laid in the water, and the phototropism of the saury is used to lure the fish into the net with the fish set lamp, and then the net is collected and caught on the boat. 丨Pixabay
However, whether it is to catch a single species or to catch multiple species of fish, there is no way to achieve complete selective capture, and it is inevitable that non-target species or substandard species will be caught. So from this point of view, the problem of by-catch is actually the result of our lack of ability to choose when we engage in fishing operations.
Such catches that exceed expectations are not in most cases a bonus. Some low-value, off-quota or regulatory catches are discarded. Most of these catches are dead or dying when they are abandoned. Therefore, bycatch first brings about the waste of marine living resources.
The large amount of by-catch catch produced when shrimp are caught using trawls. Sometimes these bycatch catches are processed into feed. 丨wikimedia
For species with high reproduction rates and high natural mortality rates, the impact of bycatch may be less, but for species such as cetaceans, sea turtles, and seabirds, where low reproductive rates and low natural mortality rates, the impact of bycatch is much greater. Under the influence of bycatch, some marine life populations have been greatly reduced, and some species have even embarked on the road to extinction.
Longline is a type of fishing gear that mainly catches high-value fish, including tuna and swordfish. It releases a long trunk line, uses floats to float on the surface of the water, and connects many branch lines with fish hooks under the trunk line, which is equivalent to dropping thousands of fish hooks at once.
Schematic of longline fishing. 丨 Ecomare, Oscar Bos / wikimedia
This method of fishing has accidentally caused the death of seabirds. When the crew hangs bait on the hook or discards the internal organs, it is very easy to attract seabirds to grab food. If the seabirds that come to grab food are not careful, they will be hooked by the bait hook and drown in the water.
BirdLife International's seabird researchers estimate that about 160,000 seabirds die each year due to longline fishing, and the most affected birds include albatrosses and seagulls. The study also found that the decline in albatross populations in recent years is closely linked to longline fishing.
Birds mistakenly caught by lensnets. 丨 U.S. Fish and Wildlife Service Headquarters / wikimedia
Turtles, which are relatively large and do not swim fast, are naturally very vulnerable to the threat of catchover. Statistics show that between 1990 and 2008, about 85,000 sea turtles were caught worldwide by gillnets, trawlers and longlines.
Gillnets are caught in a wide range of objects, they are placed in the water and rely on buoyancy to open the net vertically. Past fish, shrimp, crabs and shells were tattooed on the net. 丨Pedro Ramirez Jr. / wikimedia
But this data is based on only a small number of observed and recorded fisheries reports, so the actual by-game capture of sea turtles in the global fisheries may be two orders of magnitude larger.
Schematic diagram of the bottom trawling. 丨 afma.gov.au
For small cetaceans, gillnets, stream gillnets, seine nets, which are a huge threat. The effects of bycatch on small cetaceans may be more familiar with the story of Phocoena sinus, a porpoise in the Gulf of California.
With a maximum body length of less than 1.5 meters, the California Bay Porpoise is the smallest dolphin in the world, so named because it is only found in the northern Gulf of California. Their fate, along with the Gulf of California totoaba macdonaldi, also found in the Gulf of California, is unexpectedly linked.
California Bay porpoises. 丨Paula Olson NOAA / wikimedia
The "tonic" money gel traditionally comes from the Bahaba taipingensis of the totoaba family. As the number of yellowlips declined dramatically, merchants began to turn their attention to another species of totoaba across the ocean, the Gulf of California totoaba.
Illegal fishing of totoabas in the Gulf of California using gillnets has made the California Bay porpoise, which is similar in size to totoaba, a target for bycatch. In just over two decades, the population of porpoises in California Bay has dropped from about 600 at the end of the last century to 19 today. Ex situ conservation of the only remaining Porpoises in the Gulf of California failed at the end of 2017.
The California Bay porpoise seems to have escaped the fate of extinction.
Schematic diagram of a gillnet. 丨Michigan Sea Grant / NOAA
No.3 What can we do as consumers
While the problem of bycatch, which pervades fisheries, cannot be avoided, fisheries practitioners have made some efforts to reduce the impact of by-catch on other non-target species.
People first made many improvements in fishing gear. For example, the Turtle Excluder Device (TED) is installed on the trawler to allow the turtles who have strayed into the net to escape; the bird repellent device is added to the longline, which increases the weight of the fishing line so that the hook sinks rapidly, and the bait loading speed is improved to keep the seabirds away from the baited hooks; and the acoustic scare device (Pingers) is added to the gill net to remind marine mammals to stay away from these difficult gill nets.
Schematic diagram of the turtle escape device. Turtles can easily escape, while other catches continue to be left in the net. 丨Special Biology Society Malaysia Branch / Twitter
In terms of policies and regulations, fisheries managers have also established closed periods and closed areas, and established by-catch quotas to reduce catches of non-target species. Although fishery bycatch as an important feature of fisheries will always exist, with the development of fishery science and the efforts of fishery practitioners, the probability of fishery bycatch is gradually decreasing.
Add an acoustic scare device to drive dolphins away from gillnets. 丨 futureoceans.com
As a consumer, there seems to be little we can do about reducing bycatch. But we can still support the sustainable development of marine living resources through the selection of seafood.
In many countries and regions around the world, the corresponding "Seafood Selection Guide" has been launched. Although the types listed in these guidelines are inconsistent for regional reasons, the assessment principles are largely similar: preference is given to the purchase of seafood that is more resource-rich, farmed, at the bottom of the food chain and produced in a sustainable manner, as such seafood resources are more environmentally friendly.
For Chinese consumers, when choosing seafood on a daily basis, we can refer to the Seafood Selection Guidelines launched by WWF Hong Kong Or the Taiwan Seafood Selection Guidelines recommended by the Taiwan Fish Database.
When it comes to eating seafood, we should know a little more about things other than their tastes, and make rational choices after understanding them. Only in this way can the good wish of "fish every year" be realized forever.
Author: Sundayhao
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