Sea Turtles

Overview

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Partners

Archipelagos is a partner of the Mediterranean Science Commission (CIESM) JELLYWATCH program, which gathers baseline data on the frequency and extent of jellyfish outbreaks across the Mediterranean Sea for the first time.

The threat of jellyfish blooms

Oceans around the world are being exposed to devastating destruction due to anthropogenic threats. Ecosystems commonly struggle to find stability, faced with overfishing, increasing sea temperatures and more. As key species struggle to cope with these factors, biodiversity finds itself susceptible to more primitive species groups such as jellyfish.

 

There are many trophic levels by which, when threatened, provide space for jellyfish blooms to infiltrate. Jellyfish thrive when oceans experience the following:

  • A collapse of small fish that live closer to the sea surface, such as sardines or anchovies. These are species that feed on jellyfish and when their populations decrease, predation pressures on jellyfish plummet. Impacts are later amplified as jellyfish numbers begin to increase, remaining individuals of fish populations are often out competed for resources of zooplankton.
  • Overfishing. As fish stocks are depleted due to human action, jellyfish populations increase. This initial action perpetuates the permanent removal of commercial fish from our oceans. Jellyfish prey upon the eggs and larvae of fish species, making it impossible for populations to not fall inferior to the already increasing number of jellyfish. 
  • Destructive fishing practices. Trawling and other methods of fishing that damage the seabed and all of its inhabitants, create optimal conditions for jellyfish. By removing all predators while simultaneously leaving behind a rocky damaged habitat, jellyfish are able to outcompete all remaining life.

Species

Common name

Loggerhead Turtle

Latin name

Caretta Caretta

Order

Testudines

Family

Cheloniidae

Life span

Between 45-65 years

Nesting behaviour

Loggerhead turtles nest on sandy beaches between August and September. Females lay five times a season with an average of 110 eggs per nest.

Weight

Averages around 135kg

Carapace length

Around 90cm

Population trends

Globally, loggerhead turtles are considered ‘Vulnerable’ by the IUCN Red List. The Mediterranean is home to one of 10 subpopulations and 86,000 nests per year, but little is known about this specific population.

Distinctive Features

Their skin ranges from yellow to brown in colour with a typically red to brown shell. They can be identified by their five vertebral scutes (shell plates) and hooked beak.

Diet

Crustaceans, molluscs, jellyfish and some fish species.

Main threats

Coastal development degrading nest sites, by-catch, plastic and light pollution and climate change.

Habitat

They spend most of their lives in shallow coastal waters and open ocean, only coming ashore to nest.

Interesting fact

Female loggerheads return to the beach they were hatched to lay their eggs.

All Media © Archipelagos Institute of Marine Conservation

Common name

 Green turtle

Latin name

Chelonia mydas

Order

Testudines

Family

Cheloniidae

Life span

Up to 90 years

Nesting behaviour

Green turtles nest in the eastern Mediterranean between July and September. Females lay on average 110 eggs per nest.

Weight

Up to 190kg

Carapace length

Up to 114cm

Population trends

Globally, green turtles are considered ‘Endangered’ by the IUCN Red List as the number of mature females has declined by 48% to 67% over the past three generations. The Mediterranean is home to roughly 1,500 nests per year.

Distinctive Features

The green turtle is named for the colour of the fat under its shell and has a carapace that has various colour patterns over its life. They can be distinguished from loggerhead turtles by the presence of a single pair of prefrontal scales and four vertebral scutes.

Diet

They have a mainly herbivorous diet of seagrass and seaweeds.

Main threats

Coastal development degrading nest sites, by-catch, plastic and light pollution and climate change.

Habitat

They prefer shallow coastal waters and inshore bays

Interesting fact:

Green turtles can hold their breath for up to five hours!

All Media © Archipelagos Institute of Marine Conservation

Common name

Leatherback turtle

Latin name

Dermochelys Coriacea

Order

Testudines

Family

Dermochelyidae

Life span

Up to 50 years

Nesting behaviour

There have been no documented leatherback nesting sites in the Mediterranean.

Weight

Up to 500kg

Carapace length

Up to 1.8m

Population trends

Globally, leatherback turtles are considered ‘Critically Endangered’ by the IUCN Red List. The population remains migratory in the Mediterranean.

Distinctive Features

Recognisable by its size, dark colouration and soft, leather-like carapace made of skin and oily flesh (giving the turtle its name).

Diet

Primarily jellyfish, but they can feed on other soft-bodied organisms such as tunicates and cephalopods.

Main threats

Coastal development degrading nest sites, by-catch, plastic and light pollution and climate change.

Habitat

Leatherbacks are found primarily in the open ocean.

Interesting fact

Leatherbacks are the largest of all living turtles and one of the largest reptile species on Earth.

All Media © Archipelagos Institute of Marine Conservation