The Marine Conservation Society wants to know if you’ve seen any basking sharks, turtles or jellyfish – in UK and Irish waters.
Jellyfish? Yes, because jellyfish are the favourite food of Leatherback Turtles. And they don’t just want to know about live jellyfish but about strandings on beaches as well. Identification of live jellyfish is usually easy but once they’ve washed up on the beach it can become more difficult. They want you to therefore send photos if possible, and offer a jellyfish identification guide.
Leatherback turtles (Dermochelys coriacea) are the largest species of turtle, and occasional visitors to the North and Irish seas. By comparing the distribution of jellyfish with environmental factors such as sea temperature, plankton production and current flow, the Marine Conservation Society (MCS) hope to understand what influences the seasonal distribution of jellyfish and leatherbacks in UK waters.
The basking shark (Cetorhinus maximus) is Britain’s largest fish. They can grow up to 11 metres long and weigh up to 7 tonnes – about the size and weight of a double-decker bus. Once numerous in the UK basking sharks were hunted for their liver oil and their populations declined to such an extent that now they are considered to be endangered in UK waters. The MCS Basking Shark Watch programme has generated the largest basking shark sightings database in the world and is instrumental in identifying surface feeding hotspots.
The UK’s first State of Nature report, which has been launched by Sir David Attenborough, reveals that 60% of UK wildlife species are in decline. And that is just the species which have been well studied. Our ability to monitor the state of nature, and respond with appropriate conservation action, is hampered by a lack of knowledge on trends for most of the 8,500 marine species.
The UK’s marine area covers over 850000 km2: that’s three times more than her land area. Her seas regularly host 13 species of marine mammal and even leatherback turtles. When divers first visit UK seas they are often amazed at the diversity and abundance of life (although, in winter, they are sometimes also dismayed by the cold water).
Despite its importance for wildlife, our knowledge of the state of our seas is poor. This lack of knowledge hampers our ability to assess the impact of man’s activities. Species commercially fished are the best known. The state of UK fish stocks has improved recently but overall 75% of EU fish populations continue to be overfished. Skates and rays are no longer viable commercial species in many areas. Since 1996, harbour seals have declined by 31% in Scottish waters, particularly around Orkney (which showed a 66% decline) and northern Scotland, due to a combination of factors including pollution, disease, prey availability and competition with grey seals. From the 1950s to the 1990s, grey seal pup production increased consistently, but it is no longer increasing in some regions.
There is evidence that sub-tidal marine sediment habitats have been damaged over large areas by fishing activity, in particular by bottom-trawl and scallop dredge gear. Such activities can have huge impacts on bottom-dwellers such as the ocean quahog, a remarkable bivalve mollusc that can live for 500 years! At a more local scale, these activities also damage sensitive features, such as maerl beds and seagrass, that shelter a range of wildlife.
Sharks, skates and rays face continuing declines and are severely depleted all around the Scottish coast, in part due to overfishing. Elsewhere, most commercial fish stocks around the UK remain depleted, though there have been improvements in stocks of certain species in the last 5–10 years.
Historically, however, national and international fish landings are a fraction of the highs in the 1960s and 1970s, and generally smaller than in the early 20th century. The problems of overfishing and discards are being discussed as part of the reform of the EU Common Fisheries Policy.
The continuous plankton recorder has been monitoring plankton in UK waters since 1931. These small plants and animals form the base of our marine food webs and play a pivotal role in the ecosystem by regulating larval fish stocks. Since 1950, there have been substantial changes to the main animal group within the plankton – copepods.
The total abundance of copepods has declined markedly, and the species present are changing as the sea warms. Already, these changes are negatively affecting fish species, such as cod, as well as seabirds.
At a smaller scale, there are almost no areas of pristine marine biodiversity left around the UK, as a result of increasingly intensive human pressures. Not only are fewer fish caught today compared with 20th century baselines, but they are also significantly smaller and they mature at a younger age. This is because the relative abundance of small and early maturing species increases as a result of overfishing.
Plastic pollution is a persistent problem in all areas. There have been significant recent improvements in water quality, however, due to the treatment of land-based discharges and international laws on marine pollution from ships.
Heads of leading UK conservation organisations are putting their names to a letter calling on David Cameron to act now for nature.
For eastern Pacific populations of leatherback turtles, the 21st century could be the last. New research suggests that climate change could exacerbate existing threats and nearly wipe out the population.
When leatherback turtle hatchlings dig out of their nests buried in the sandy Playa Grande beach in northwest Costa Rica, they enter a world filled with dangers. This critically endangered species faces threats that include egg poaching and human fishing practices. Now, Drexel University researchers have found that the climate conditions at the nesting beach affect the early survival of turtle eggs and hatchlings. They predict, based on projections from multiple models, that egg and hatchling survival will drop by half in the next 100 years as a result of global climate change.
“Temperature and humidity inside the nest are significant factors affecting egg and hatchling survival,” said Dr. James Spotila, the Betz Chair Professor of Environmental Science in Drexel’s College of Arts and Sciences. Spotila and colleagues therefore examined the relationship between regional climate patterns with leatherback turtles’ nesting success over six consecutive nesting seasons at Playa Grande. This beach is the major nesting site for leatherback turtles in the eastern Pacific Ocean, containing more than 40 percent of nests.
“We have discovered a clear link between climate and survival of this endangered sea turtle population,” said Spotila.
The researchers found that warmer, dryer El Niño conditions were associated with significantly higher mortality for eggs and hatchlings. Using projections of global climate change due to global warming over the next 100 years, they predicted that El Niño conditions will become more frequent and hatchling success will decline throughout the 21st century at Playa Grande and other nesting beaches that experience similar effects.
Leatherback turtles are the largest on Earth, growing up to two meters long and exceeding 900 kilograms. They are critically endangered. Some of the most important populations have collapsed. For example, the rookery in Malaysia, which from 10,155 clutches in 1956 fell to 37 in 1995 in the same stretch of beach.
Leatherbacks can be found in the tropic and temperate waters of the Atlantic, Pacific, and Indian Oceans, as well as the Mediterranean Sea. Adult leatherbacks also traverse as far north as Canada and Norway and as far south as New Zealand and South America. Unlike other reptiles, leatherbacks are able to maintain warm body temperatures in cold water.
Tagging and tracking leatherback sea turtles has produced new insights into the turtles’ behavior in a part of the South Pacific Ocean long considered an oceanic desert. According to researchers at Stanford University, the new data will help researchers predict the turtles’ movements in the ever-changing environment of the open ocean, with the goal of reducing the impact of fishing on the endangered leatherback population.
Leatherback turtles have suffered a massive 90 percent drop in their population in the eastern Pacific Ocean over the last 20-plus years, largely at the hands of humans
Now, new data from a 5-year-long project tagging and tracking the turtles are providing insights into their behavior, explaining why they congregate for months in what appeared to be one of the most nutrient-poor regions in the oceans, the South Pacific Gyre, and also helping researchers predict their movements on the high seas.
This new view of the lives of leatherbacks could offer a way to keep the turtles out of harm’s way and give their numbers a chance to rebound.
Until now, researchers didn’t know why the leatherbacks that nest at Playa Grande in Costa Rica headed for the gyre and lingered for months. Satellite surface data suggested that this area spanning the Pacific Ocean between South America and New Zealand, from the low to mid-latitudes, appeared to be a virtual desert in the ocean, largely devoid of nutrients.
However, the presence of substantial tuna and swordfish fisheries within the region suggested there must be ample forage of some sort available.
Because only limited data exist concerning the diversity, abundance and distribution of the leatherback’s favorite prey – gelatinous zooplankton, such as jellyfish – within the South Pacific Gyre, no one knew whether the turtles had food down there or not.
But the data that came back from the tagged turtles suggest there may be plenty of jellyfish on which to feast.
One of the biggest hazards leatherbacks face on the high seas is longline fishing, a widely used approach for capturing commercially valuable species such as tuna and swordfish. The turtles also face fishing pressure from gill nets and longlines as they swim through coastal waters on their way out to the open ocean.
The problem, George Shillinger, lead author of a paper to be published in Marine Ecology Progress Series, said, is that areas that attract commercially desirable species also tend to be attractive to leatherbacks and other non-targeted species, known as by-catch.
Temporary closure of certain areas – breeding zones, migration routes and rich foraging habitats – when turtles are most likely to be concentrated there is one possible measure to protect turtles. Modification of fishing techniques, such as deploying hooks at the depths that are least likely to be occupied by turtles, could also help.