Invasive Species in the Aegean

Overview

The environmental impacts of invasive species has raised global concern as their presence has the potential to cause devastation to biodiversity and benthic community structure. These species are threatening due to their ability to outcompete native species for food and niche. This often results in the impeding faunal and floral species eventually replacing local individuals. 

It is vital that we track the spread of these invasive species, in order to preserve community structures endemic to the Mediterranean. Invasive species have become such a threat that more than 5% of the marine species in the Mediterranean are now considered non-native species. This amounts to over 986 alien species, of which 775 were found specifically in the eastern Mediterranean.

Partners

Species

FISH

MACROINVERTEBRATES

MARINE FLORA

FISH

Common Name

Indo-Pacific sergeant

Scientific Name

Abudefduf vaigiensis

Description

Small compressed oval body covered in small, fine scales. Vibrant coloration of yellow to pale-blue/green with  5 vertical stripes down their sides.

Habitat

Shallow water (<20m), associated with a variety of substrate.

diet

Zooplankton, benthic algae and invertebrates

Size

5-15cm

Status according to ELNAIS

Alien – Casual

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the  Indo-Pacific, potentially via shipping activity

first sighting in greek waters

Disputed because of confusion with similar species, potentially 2018

edible?

No

Impacts

Shows some evidence of hybridisation with native species, diminishing the strength of native gene pools.

further information

The males remain at spawning sites to guard and aerate the eggs

Common Name

Shrimp scad

Scientific Name

Alepes djedaba

Description

Sleek body adapted for open water swimming. Bright, golden yellow/green body with many bold vertical bands down their sides as juvenilles, which may fade during adulthood. Their fins display a pale yellow coloration.

Habitat

Shallow inshore reefs and sandy substrates

diet

Invertebrates such as shrimps and crustacean larvae, and sometimes small fish

Size

25cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Red Sea

first sighting in greek waters

Zakynthos, 1960

edible?

Yes

Impacts

They school with T.mediterraneus, and share the same dietary niches

further information

Possibly overexploited in its native areas, e.g., India, for human consumption

Common Name

Pharaoh cardinalfish

Scientific Name

Apogonichthyoides pharaonis

Description

The Pharaoh cardinalfish has a streamlined body with striking red and orange colouration dorsally and a palewhite or yellow underside. A thin, black stripe runs vertically through their eye, with a wider black line extending from their grill cover over the lateral line to the caudal fin.

Habitat

Worldwide distribution with a preference for rocky substrates and shallow waters

diet

Nocturnal planktivorous predator

Size

4-6cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Red Sea

first sighting in greek waters

Rhodes, 2002

edible?

No

Impacts

Outcompete Apogon imberbis

further information

Mouth-brooder

Common Name

Red Sea hardyhead silverside

Scientific Name

Atherinomorus forskalii

Description

These fish are characterized by a bright, iridescent silvery-blue body with several prominent yellow to golden horizontal stripes running along their streamlined body. The dorsal fin is located closer to the tail end of the body and is typically marked with a series of small spots.

Habitat

Tropical, often associated with reefs and other sheltered habitats

diet

Opportunistic feeder, prey includes zooplankton and benthic invertbrates

Size

10-12cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant

first sighting in greek waters

Kos, 1986

edible?

Yes

Impacts

Diet overlap with Atherina boyeri and  Belone belone

further information

Can form schools of thousands

Common Name

Blotchfin dragonet

Scientific Name

Callionymus filamentosus

Description

The blotchfin dragonet is a light brown fish that has darker brown spots. Males have a dorsal spine before the first dorsal fin. For both sexes, the second dorsal fin is noticably longer than the first.

Habitat

Sandy and muddy substrate in coastal areas to around 100m, although they have been recorded at depths as great as 350m

diet

Feeds on small benthic invertebrates, mainly crustaceans and marine worms.

Size

Up to 20cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Indo-West Pacific

first sighting in greek waters

Ionian sea, 2003

edible?

No

Impacts

As their population size has increased rapidly closely related species have seen massive population declines.

further information

Callionymus filamentosus are victims of a castrating parasite, Obruspora papernae that is found in most of the Mediterranean population. Despite this, they remain one of the most abundant fish species represented in shallow trawler fishery landings on the Israeli Mediterranean coast.

Common Name

Fangtooth moray

Scientific Name

Enchelycore anatina

Description

These morays have large teeth resembling fangs, and are typically dark brown or black with white or yellow spots. They have an elongated body and an absence of pectoral and pelvic fins, as well as a lack of scales.

Habitat

Rocky reef crevices, concealing itself for elusive predation, juveniles can also be found at great depths

diet

Hunts fish and cephalopods

Size

120cm

Status according to ELNAIS

Unknown

Pathway of Origin

Unknown

Origin

Migrated through the Strait of Gibraltar from the eastern-central Atlantic

first sighting in greek waters

Elafonissos Island, 2002

edible?

No

Impacts

Muraena helena occupy the same niche.

further information

These are solitary animals

Common Name

Bluespotted cornetfish

Scientific Name

Fistularia commersonii

Description

The bluespotted cornetfish with very elongated and highly compressed body structure, often confused with drifting seagrass in the deep waters. Body color typically greenish-grey with a whiter underside, it features subtle blue stripes or dots.

Habitat

Occurs at depths between 0-132m on shallow coral and rocky reefs and sandy bottoms as well as Posidonia and Cymodocea meadows

diet

Feeds predominently on other fish, as well as shrimp and isopods.

Size

160cm

Status according to ELNAIS

Alien – Invasive

Pathway of Origin

Unaided

Origin

Lessepsian migrants, native to the Pacific and Indian Oceans

FIRST SIGHTING IN GREEK WATERS

Crete, 2001

edible?

Yes, in high demand

Impacts

Spicara smaris, Boops boops, and Mullidae species were found to be their most common prey type by weight

further information

A widespread species, found from Japan to the Meditteranean, it is related to pipefish and seahorses.

Common Name

Black-barred halfbeak

Scientific Name

Hemiramphus far

Description

A long, thin fish with a long beak-like lower jaw that protudes outwards from its body. It’s shorter upper jaw can be described as triangular and lacking scales. Mainly silver with a bluer dorsal region, a number of black vertical lines are found along the side of the body.

Habitat

Epiepelagic (0-6m), coastal waters

diet

Variable feeding habits, but mainly zooplankton and unmoored seagrass blades in surface waters.

Size

Up to 45 cm

Status according to ELNAIS ​

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Indo-West Pacific

first sighting in greek waters

Rhodes, 1943

edible?

Yes

Impacts

Negligible or unreported.

further information

One of the first lessepsian migrants to the Mediterranean

Common Name

Silver-cheeked toadfish

Scientific Name

Lagocephalus sceleratus

Description

This toadfish boasts a greenish body adorned with dark spots enveloping its upper half. A distinct white belly is set apart from the spotty upper portion by a silver encircling line.

Habitat

Found in warm, shallow waters, with sandy and muddy substrates

diet

Demersal carnivores, feed mainly on non-native species molluscs and crustaceans

Size

40-60cm

Status according to ELNAIS

Alien – Invasive

Pathway of Origin

Unaided

Origin

Lessepsian migrants, possibly transported in ship ballast water

first sighting in greek waters

Zakynthos, 2005

edible?

No, it is incredibly toxic

Impacts

In part due to their lethal toxicity, silver cheeked toadfish are massively succesful predators within Eastern Meditteranean waters. They have inhabited the niche of many native top predators of the ecosystem that have dissappeared due to overfishing. Surprisingly, they do seem to benefit the ecosystem by predating many other invasive species.

further information

An important part of the ecological sucess of L. sceleratus is due to their having one of the most advanced forms of teeth in the animal kingdom. The ‘first generation teeth’ are coated with recurring toothbands which are continously regenerated by stem cells.

Common Name

Red Sea goatfish

Scientific Name

Parupeneus forsskali

Description

In addition to the two chin barbels typical of goatfish, this fish can be identified with its elongated body and a bold black stripe that runs from the upper lip through the eye and along the upper body, ending near the second dorsal fin. Above the stripe, the body is grayish-green with yellow scale edges, while below, coloration is white with reddish scale edges.

Habitat

Sandy bottoms and coral reefs, often in the vicinity of seagrass meadows. Found at depths of up to 45m

diet

Carnivorous, mostly preys on small benthic crustaceans and molluscs

Size

25cm

Status according to ELNAIS ​

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrants native to Atlantic, Indian and Pacific oceans. 

first sighting in greek waters

Rhodes, 2017

edible?

Yes

Impacts

This invasive mullid competes with native mullid species.

further information

Probes the sand with sensory organ-carrying hyoid barbels.

Common Name

Fish in this genus are commonly referred to as sweepers, but this species has no common name

Scientific Name

Pempheris rhomboidea

Description

Elongated, slender body with scales displayed in a diamond formation. The diamond pattern is outlined in black, making it stand out from their pale body.

Habitat

Pelagic/neritic, minimum depth of 20m

diet

Zooplankton

Size

Up to 13.2cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Red Sea

first sighting in greek waters

Rhodes, 1983

edible?

Rarely consumed

Impacts

Reported to be populous underneath offshore fish farms in the Aegean, altering the dispersal and biodiversity of native fish due to human intervention.

further information

Exhibits underwater soniferoius behaviour

Common Name

So-iuy mullet

Scientific Name

Planiliza haematocheilus

Description

The fusiform body can be silver to brown in colour on the top of the body, however the bottom half is colourless. It has an caudal fin that has a stronger, more bolder colouration compared to the rest of the body. It has two separate dorsal fins and a small mouth with a thick upper lip.

Habitat

Euryhaline species that displays high ecological plasticity, typically found in near-shore water

diet

Omnivorous, often consumes detritus

Size

50cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Native to north-east Asia, escaped from fisheries

first sighting in greek waters

Rhodes, 1998

edible?

Yes

Impacts

A danger to native mullet species, they bring exotic parasites that have a wider influence on all nearby fauna and are often found in close proximity with Liza aurata, allowing parasite transfer.

further information

Native to an area with many cyclic changes in water composition; can hibernate in winter

Common Name

Striped eel catfish

Scientific Name

Plotosus lineatus

Description

This species of catfish has a cylindrical, elongated body covered in a mucus layer. Brrownish grey stripes run vertically along the body, with a set of 4 barbels by the mouth. It has a single venomous spine on each of the pectoral and dorsal fins.

Habitat

Mainly associated with reefs, with a depth range from 1- 60m

diet

Carnivorous, search sand for molluscs, worms, fish and crustaceans

Size

25cm

Status according to ELNAIS

Unknown

Pathway of Origin

Unknown

Origin

Lessepsian migrant, native to the  Indo-Pacific

first sighting in greek waters

Dodecanese, 2016

edible?

Edible with caution, due to being one of the most venomous species globally

Impacts

Compete with Trachinus draco and Mullus sp for prey

further information

Juvenilles form dense aggregations of around 100 fish, in a distinctive ball shape

Common Name

Common lionfish, Devil firefish

Scientific Name

Pterois miles

Description

This fish is well-known for its invasive propensity and is easily recognized with red, white, and black stripes and long spines that are very toxic. It typically swims slowly, passively drifting in the water while hunting for prey.

Habitat

Will settle in a majority of habitat types, but prefers rocky caves and crevices (often previously occupied by groupers) up to 150m deep

diet

Generalist predator that consumes a range of teleosts and crustaceans, some of which have high economic value, thus competeing with fisheries.

Size

30-40cm

Status according to ELNAIS

Alien – Invasive

Pathway of Origin

Unaided

Origin

Lessepsian migrants native to the Red Sea and Indian Ocean

first sighting in greek waters

Kalymnos, 2009

edible?

Yes

Impacts

They inhabit the same range as Pempheris species, Apogon species and Sarcocentron rubrum, pushing them out of their native habitat or consuming them; Spicara smaris, Sparisoma cretense, Chromis chromis, are all target species for lionfish consumption.

further information

They can live up to 30 years and have few predators.

Common Name

Redcoat

Scientific Name

Sargocentron rubrum

Description

The main body is enveloped by brownish-red and white stripes and has a dark red dorsal fin that is interrupted by white blotches on the membrane. Additionally, five vertical stripes adorn its cheek, extending from the back of the cheek to its large eyeball, running perpendicular to the body stripes.

Habitat

Nocturnal; rocky substrate from 0-40m, pelagic when juvenile then migrate to rocky inshore habitat after losing juvenile spines, and are found in caves during the day.

diet

Mainly on decapod crustaceans

Size

Up to 32cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Red Sea

first sighting in greek waters

Rhodes, 1948

edible?

Yes

Impacts

Competes with Apogon imberbis, they inhabit the same rocky ground nocturnally

further information

Sharp, long, venomous spines line its cheeks

Common Name

Lessepsian lizardfish

Scientific Name

Saurida lessepsianus

Description

The Lessepsian lizardfish is recognized by its triangular dorsal fin with 11-12 rays, long pectoral fins, and a caudal fin bearing 3-8 black spots. Its belly has a front portion ranging from pale grey to black, while the rear is whitish. Notably, it features a large mouth with a series of teeth that grow larger towards the back.

Habitat

Depth range of 20-100m, sandy and muddy marine substrates

diet

Piscivorous, low diet plasticity

Size

Up to 28cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Red Sea

first sighting in greek waters

Dodecanese, 1971 (potentially prior)

edible?

Yes

Impacts

High diet overlap with native Synodus saurus

further information

Only identified in scientific literature in 2015, before specimens were thought to be of similar species.

Common Name

Blue-barred parrotfish

Scientific Name

Scarus ghobban

Description

This parrotfish has an elongated, compressed body, with a beak-shaped mouth used for grazing on hard substrates. It has extremely striking colouration; an anterior of vibrant blue or green meets an oragne or pink posterior.

Habitat

0-90m, Adults are found among coral reefs, while juveniles prefer algae covered inshore habitats.

diet

Like other parrotfish, it feeds by scraping algae from rock and coral

Size

Usually 30cm, but up to 75cm has been recorded

Status according to ELNAIS

Alien – Casual

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Red Sea

first sighting in greek waters

2014

edible?

Yes

Impacts

Crushing and consumption of native corals and algae

further information

Maximum age of 13 years

Common Name

Narrow-barred Spanish mackerel

Scientific Name

Scomberomorus commerson

Description

With a body shape specifically adapted for speed, they have a pointed head and several dorsal and ventral fins to aid stability. They have a silvery, bluish-green body with many slim, vertical bars which may vary between black and deep blue. Their underside is most commonly white or silver.

Habitat

Pelagic, continental shelves to shallow coastal areas between 10-70m

diet

Low diet plasticity with their main food source being the anchovy, Engraulis encrasicolus, They also eat squid and shrimps.

Size

120cm

Status according to ELNAIS

Unaided

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Indian Ocean

first sighting in greek waters

Ionian Sea, 2008

edible?

Yes, in high demand

Impacts

E. encrasicholus, Boops boops, T. mediterraneus; all are native prey species

further information

Can live up to 22 years

Common Name

Dusky spinefoot

Scientific Name

Siganus luridus

Description

This fish’s colouration is a mottled dark green and brown, with stronger pigmentation in the top half of their body. The anterior spines are slender yet powerful; the posterior spines are stout, all are venomous.

Habitat

Shallow water with hard substrates such as coral and rocky reefs. In Posidonia meadows in Rhodes.

diet

Herbivores that graze on algae in the subrate as well as larger brown algae

Size

20-30cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the western Indian Ocean

first sighting in greek waters

Crete, 1964

edible?

Toxic spines, but if prepared properly can be consumed

Impacts

Their algal grazing encourages urchin activity

further information

Around Santorini, this species accounted for 90% of the total abundance of herbivores

Common Name

Marbled spinefoot

Scientific Name

Siganus rivulatus

Description

The marbled spinefoot has a body with brown, green or grey coloration and a lateral midline. The fish’s eyes are silver or gold and notably it has protruding venomous dorsal spines that are displayed when threatened.

Habitat

Prefers sheltered areas such as shallow waters with hard substrates and strong algal communities

diet

Herbivorous, algae grazer

Size

20-27cm

Status according to ELNAIS

Alien – Invasive

Pathway of Origin

Unaided

Origin

Lessepsian migrants; native to the Indian Ocean and the Red Sea to the Mediterranean

first sighting in greek waters

Crete, 1925

Edible?

Yes

Impacts

These fish have the same dietary niche as Sarpa salpa, Sparisoma cretense, and many juvenile native fish; Siganids are far more abundant in the Mediterranean than other native herbivores

further information

This species has competitve superiority stemming from greater adaptability, rapid growth, higher fecundity and early sexual maturity.

Common Name

Yellowstripe barracuda

Scientific Name

Sphyraena chrystotaenia

Description

Like many barracudas this fish has a very elongated body with two dorsal fins and a forked tail. The underside of the fish is silvery with a darker dorsal coloration and a lateral stripe.

Habitat

Pelagic, from 1 – 50m

diet

Carnivorous, mainly preys on fish and crustaceans.

Size

20-25cm

Status according to ELNAIS ​

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Indo-West Pacific

first sighting in greek waters

Crete, 1995

edible?

Yes, becoming commercially important in the Mediterranean

Impacts

Consumes small fish that are also targeted by regional fisheries.

further information

Forms large schools

Common Name

Reticulated leatherjacket

Scientific Name

Stephanolepis diaspros

Description

A laterally compressed species with rough olive coloured scales. The first dorsal fin has a large spine, the second is filamentous and the caudal fin is rounded. It has a pointed snout and many incisor-like teeth.

Habitat

0-50m in demersal, tropical waters, around rocky substrate with vegetation, the immature individuals found on sandy and muddy substrates, sometimes found quite far off the coast.

diet

Preys on small invertebrates off rocks, omnivorous and opportunistic predators

Size

Up to 25cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Red Sea

first sighting in greek waters

Messenia, 1943

edible?

Yes

Impacts

Will consume marine plants to aid in digestion of its main prey.

further information

First described by Alec Frederick Fraser-Brunner in 1940

Common Name

Yellowspotted puffer

Scientific Name

Torquigener flavimaculosus

Description

This species has large eyes with a yellow ring surrounding the blue centre. It has a bulbous body covered in hexagonal plates for protection. It has yellow markings allowing camouflage with sand.

Habitat

Found in depths of 3-57m, near reefs, seagrass beds and soft substrates

diet

Carnivorous, preference for invertebrates with limited mobility

Size

Up to 16cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant, native to the Indian Ocean

first sighting in greek waters

Rhodes, 2006

edible?

Contain tetrodotoxin, not edible and lethal if consumed

Impacts

Predator of many native species

further information

Unique foraging strategy in which they can suck hermit crabs out of their shells

Common Name

Por’s goatfish

Scientific Name

Upeneus pori

Description

Slender body that is flattened on the underside. Their coloration is red/orange and pale silver underneath. The caudal fin has orange and silver stripes on the upper half and is solid orange on the other half, and can be distinguished by barbels underneath the mouth.

Habitat

Demersal species, found in soft and hard substrates in coastal areas between 20-52m

diet

Forages for benthic invertebrates with barbels

Size

Up to 19cm

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Lessepsian migrant

first sighting in greek waters

Iskenderun Bay, 2003

edible?

Yes, in high demand

Impacts

Competes with native mullidae sp.

further information

Has spread as far west as Sicily

Photo (c) Katerina Kalogerini, some rights reserved (CC BY-NC)

MACROINVERTEBRATES

Common Name

Spotted Sea hare

Scientific Name

Aplysia dactylomela

Description

Large sea slug with distinctive black rings of varying sizes covering the body which can have a pale green to yellow and dark brown base coloration. Head with four “horns”.

Habitat

Rocky shores and sand with dense algal cover, shallow waters

diet

A herbivore that feeds on green algae

DEPTH

0-40 m

Size

40 cm

Status according to elnais

Unknown

Pathway of Origin

Unaided

Origin

Cape Verde archipelago, the Caribbean and around the Gulf of Mexico, off the coast of Florida, Bermuda, Bahamas, Belize, Brazil, Senegal and the Canary Islands.

first sighting in greek waters

2002

further information

It is nocturnal during the day it hides under large rocks or in crevices. At night, it is usually seen either crawling like an ordinary sea slug on seaweeds, or swimming by undulating its wings. Mantle flattens with swimming and ripples similar to that of cuttle fish. If threatened releases magenta ink to the water

Common Name

Pygmy sea hare

Scientific Name

Aplysia parvula

Description

A small sea slug. Mottled brown or green (sometimes more uniform). Tentacle tips are dark in colour.

Habitat

Intertidal and subtidal habitats.

diet

A herbivore that feeds on red algae

DEPTH

0-50 m

Size

6 cm

Status according to elnais

Questionable

Pathway of Origin

Unaided

Origin

Red Sea and Indian Ocean

first sighting in greek waters

2006

further information

It usually occurs in less than 5 m of water. Found roaming around various species of algae. It is nocturnal.

Common Name

Ragged sea hare

Scientific Name

Bursatella leachii

Description

Large sea slug of grey brown coloration with numerous long, branching, white papillae that give the animal its ragged appearance. A key distinctive feature are the dark brown blotches on the white papillae and bright blue eyespots scattered over the body. It also has two characteristic tentacles originating from the head resembling long ears, and two oral tentacles of similar shape near the mouth.

Habitat

Shallow, sheltered waters, often on sandy or muddy bottom, seagrass beds, and occasionally in harbour environments.

diet

A detritivore that feeds on green aglae, cyanobacteria and Calothrix crustacea

DEPTH

0-30 m

Size

10 cm

Status according to elnais

Alien – Established

Pathway of Origin

Unaided, Transport – Stowaway

Origin

Tropical Atlantic and Indo-Pacific Oceans

first sighting in greek waters

1975

further information

More active during daytime and hides at night. In the early morning sea hares are found together in groups of 8–12 individuals, disperse during the day. They reassemble again at night. Often found around Caulerpa prolifera. Comercial benefits in anti-HIV medicine

Common Name

Atlantic blue crab

Scientific Name

Callinectes sapidus

Description

Decapod crustacean with distinctive blue legs and claws. Back legs are adapted for swimming.

Habitat

Inhabits the crevices of rocks or man-made structures in estuaries and river mouths. Good tolerance to high salinity water to almost fresh water.

diet

An omnivore that feeds on clams, oysters, and mussels as well as almost any vegetable or animal matter.

DEPTH

1 to 90 m

Size

18 cm

Status according to elnais

Alien – Invasive

Pathway of Origin

Transport – Stowaway

Origin

Western Atlantic, from New
England to Uruguay

first sighting in greek waters

Amphipolis and Methonis – North West Aegean Sea (1937)

further information

During times of the year when temperatures are colder, C. sapidus tends to migrate to deeper water. They are active swimmers and have their last pair of walking legs adapted to be shaped like a paddle to accommodate swimming. It is a diurnal animal

Common Name

Upside-down jellyfish

Scientific Name

Cassiopea andromeda

Description

Scyphozoan jellyfish with yellow-brown bell, pale spots and streaks with frilly tentacles. Lies upside down on the seabed, easily mistaken for an anemone.

Habitat

Sandy or clear, warm and shallow waters

diet

Feed on small pelagic species, which are near the seabed. They recieve nutrients from a symbiotic relationship with macroalgae.

DEPTH

> 7.5 m

Size

30 cm

Status according to elnais

Alien – Established

Pathway of Origin

Unaided

Origin

Indo-Pacific

first sighting in greek waters

Therasia Island (1942)

further information

Prey on fish larvae/eggs and could therefore negatively affect fisheries

Common Name

None

Scientific Name

Cerithium scabridum

Description

Sea snail with brown to green coloration and long proboscis. Shell is long and gets wider close to the opening and tapers to the end.

Habitat

Intertidal or shallow water zone sandy mud, rock pools in sheltered places, and lagoons.

diet

A herbivore that feeds on graze on algae and dertitus

DEPTH

2 – 25 m

Size

7 cm

Status according to elnais

Alien – Established

Pathway of Origin

Unaided

Origin

Red Sea, Persian Gulf, western and southern India

first sighting in greek waters

2007

further information

Nocturnal – does its foraging at night

Common Name

Jewel box oyster

Scientific Name

Chama pacifica

Description

White to pinkish-red with pale-rose blotches. Large, ovoid-shaped oyster. Usually thick and irregularly rounded.

Habitat

Rocky shores and hard substrates, thrive in harbour environments

diet

A filter feeder that feeds on phytoplankton & bacteria

DEPTH

0 – 40 m

Size

8 – 10 cm

Status according to elnais

Alien – Established

Pathway of Origin

Unaided

Origin

Indo-Pacific

first sighting in greek waters

Rhodes Island (2005)

further information

Singly or together with Erythrean spiny oyster can form dense aggregations, producing solid reefs at some sites and completely replacing native species.

Common Name

Persian conch

Scientific Name

Conomurex persicus

Description

Elongated white shell, densely covered in a brown sstriped pattern.

Habitat

Sandy bottoms between 1 and 10 m deep

diet

A herbivore that feeds on algae

DEPTH

3 – 8 m

Size

4 – 7 cm

Status according to elnais

Alien – Invasive

Pathway of Origin

Unaided, Transport – Stowaway

Origin

Western Indian Ocean

first sighting in greek waters

Rhodes Island (1988)

further information

Buries itself during the winter months starting in October/November and ends its dormant state in April. Poisonous. It is a nocturnal species.

Common Name

Leaf Oyster

Scientific Name

Dendostrea folium

Description

A red-brown coloured shell with an irregular elongated shape. Two valves – right valve dark purple, left valve white with purple stripes.

Habitat

Shallow, sublittoral, on rocks.

diet

A filter feeder that feeds on bacteria, protozoa, a variety of diatoms and invertebrate larvae

DEPTH

5 – 30 m

Size

Up to 55 mm in height, 30 in length and 10 in width

Status according to elnais

Alien – Invasive

Pathway of Origin

Unaided, Transport – Stowaway

Origin

Indo-West Pacific

first sighting in greek waters

2005

further information

Attached to other living sessile bivalves.

Photo (c) wayneking, some rights reserved (CC BY-NC)

Common Name

Long-spined sea urchin

Scientific Name

Diadema setosum

Description

Echinoid with black test and very long and narrow spines, which can be black, white or banded black and white. It also has 5 characteristic white dots on its body and an orange ring around the periprotcal cone. Mildly venomous.

Habitat

Can be found on sandy area, near seagrass beds or rocks

diet

A herbivore that feeds on green and filamentous algae

DEPTH

0-70 m

Size

Up to 10 cm, spines up to 30 cm

Status according to elnais

Alien – Established

Pathway of Origin

Unaided

Origin

Indian Ocean, East Africa and the Red Sea. Also in South Pacific Islands and Japan.

first sighting in greek waters

2010

further information

Lives in a group or alone. Hides in crevices and under overhangs by day, and forages at night, at a distance of a few meters away from its daytime hideout. It is nocturnal.

Common Name

Giant pink ascidian

Scientific Name

Herdmania momus

Description

A large ascidain that is translucent with pink/red colouration. Inflated, spherical body with two short, cylindrical siphons on the top and side. Tiny calcareous spicules lie under the surface of the outer tunic and internal structures.The gut can sometimes be distinguished through the transparent body, forming a loop

Habitat

Smooth artificial substrates such as breakwaters, jetties and artificial reefs

diet

A filter feeder that feeds on plankton and small organisms

DEPTH

up to 20 m

Size

18 cm

Status according to elnais

Alien – Established

Pathway of Origin

Unaided

Origin

Indo-Pacific

first sighting in greek waters

2010

further information

Have not yet been shown to outcompete native species or invade natural ecosystems. Its potential invasive status is uncertain.

Common Name

None

Scientific Name

Oculina patagonica

Description

A stoney colonial coral that is yellow-brownish in colour. Tubular skeletons of the polyps are crowded, up to 5 mm

Habitat

Natural pristine sites as well as in
marinas, harbours and heavily polluted areas.

diet

Stony colonial coral that
can harbour zooxanthellae

DEPTH

0-40 m

Size

5 mm

Status according to elnais

Unknown

Pathway of Origin

Transport – Stowaway, Transport – Contaminant

Origin

The eastern Atlantic

first sighting in greek waters

2002

further information

The colonies are generally encrusting, thicker in the centre with a thin edge spreading over the substrate.

Photo (c) Rafael Medina, some rights reserved (CC BY)

Photo (c) Bernat Espigulé, some rights reserved (CC BY-NC)

Common Name

Sally light foot crab

Scientific Name

Percnon gibbesi

Description

Decapod of brownish colour with characteristic green and yellow
rings on the legs. Eye stalks and claws are orange.

Habitat

In the crevices of rocks or on man-made structures such as ports and marinas at shallow depths.

diet

A herbivore that feeds on filamentous and calcareous algae.

DEPTH

0.5 – 4 m

Size

3 cm

Status according to elnais

Alien – Invasive

Pathway of Origin

Transport – Stowaway

Origin

Pacific (California to Chile)
and Atlantic (Florida to Brazil) American coasts. Atlantic coast of Africa

first sighting in greek waters

further information

Often hides under stones and within man made structures such as marinas and docks. It is nocturnal.

Common Name

Rayed pearl oyster

Scientific Name

Pinctada radiata

Description

Bivalve with brown-purple shell occasionally mixed with green, pale yellow or white. The shape of the shell is rounded and irregular, with the two valves being flattened and developing obliquely in one direction.

Habitat

Attached to hard surfaces (natural or artificial) such as rocks, nets, buoys and docks, as well as in seagrass meadows on sandy-muddy sediments

diet

A filter feeder that feeds on microscopic plankton and organic particles.

DEPTH

5-25 m

Size

5-10 cm

Status according to elnais

Alien – Invasive

Pathway of Origin

Escape from Confinement, Transport – Stowaway (hull fouling)

Origin

Shallow waters in the Indo-Pacific region

first sighting in greek waters

1961

further information

Creates extensive oyster beds

Common Name

Rapa whelk

Scientific Name

Rapana venosa

Description

Large sea snail with rounded and heavy shell of grey to reddish brown coloration. Ornamental axial ribs, with a whorl and as a short spire.

Habitat

On sandy and rocky mixed bottoms in marine and brackish estuarine

diet

A carnivore that feeds on Bivalve molluscs

DEPTH

0.5-25 m

Size

3 – 16.5 cm

Status according to elnais

Alien – Casual

Pathway of Origin

Unaided

Origin

Northeast Pacific

first sighting in greek waters

Thessaloniki (1986)

further information

Often lies buried in the sand to avoid predators and preys on other mollusc species. Nocturnal.

Common Name

Nomad jellyfish

Scientific Name

Rhopilema nomadica

Description

Scyphozoan jellyfish with eight characteristic large mouth-arms, divided at mid-length into two ramifications with numerous long filaments.

Habitat

Coastal areas

diet

A carnivore that feeds on vast amounts of shrimp, mollusc and fish larvae

DEPTH

0-40 m

Size

The bell of this jellyfish can range from 10 to 90 cm in diameter, usually 40 – 60 cm

Status according to elnais

Alien – Casual

Pathway of Origin

Unaided

Origin

East coast of Africa and the Red Sea

first sighting in greek waters

Peninsula of Mani (2006)

further information

Dense in summer months
but found all year round.

Common Name

Manila clam/Japanese carpet shell

Scientific Name

Ruditapes philippinarum

Description

Bivalve of oval shell, radiating ribs, variable pattern and colour (generally cream coloured).

Habitat

Estuaries and lagoons, on sandy and muddy bottoms

diet

A filter feeder that feeds on plankton

DEPTH

Buries to 10 cm depth

Size

4 – 5.7 cm

Status according to elnais

Unknown

Pathway of Origin

Unknown

Origin

Pacific to the Indian Ocean

first sighting in greek waters

1980

further information

Significantly increase sediment erosion and re-suspension rates and over-enrich sediments with biodeposits, leading to sediment anoxia which inhibits nitrification and kills benthic fauna.

Common Name

Bigfin reef squid

Scientific Name

Sepioteuthis lessoniana

Description

Cephalopod with thick, muscular, oval fins extending around the mantle. Presence of large chromatophores covering the surface of the head.

Habitat

Shallow waters, found on coral reefs and seagrass meadows

diet

A carnivore that feeds on prawns, fish and crustaceans

DEPTH

100 m

Size

3.8 – 33 cm

Status according to elnais

Alien – Established

Pathway of Origin

Unaided

Origin

Indo-Pacific – Japan to Australia and New Zealand coasts, Hawaii to the East African coast, north to Red Sea and south to Madagascar

first sighting in greek waters

2009

further information

Exhibit both schooling and shoaling behaviours. Very young bigfin reef squids will also stay close together (shoaling), but do not swim together parallel to each other (schooling). Unlike most other squid species, bigfin reef squids are rarely cannibalistic. Nocturnal. Commercially important.

Common Name

Spiny oyster

Scientific Name

Spondylus spinosus

Description

Bivalve with rust coloured shell lined with long white spines and multiple eyes around the edge of the mantle.

Habitat

Rocky substrate

diet

A filter feeder that feeds on plankton

DEPTH

2-40 m

Size

7 cm

Status according to elnais

Alien – Casual

Pathway of Origin

Transport – Stowaway (hull fouling)

Origin

Indo-West Pacific

first sighting in greek waters

2008

further information

It can form large populations of up to 15 individuals.

Common Name

Worm Sea Cucumber

Scientific Name

Synaptula reciprocans

Description

Holothurian with a very elongated body of a dark-brown to black coloration, which can appear as a long black rope to the untrained eye. Characteristic mouth surrounded by tentacles.

Habitat

Found on rocky or sandy substrate, usually close to vegetation

diet

An omnivore that feeds on diatoms and other micro-organisms and organic coated particles

DEPTH

From the surface down to 20 m

Size

40 cm

Status according to elnais

Alien – Invasive

Pathway of Origin

Unaided

Origin

Red Sea

first sighting in greek waters

1995

further information

They are surficial modifiers, distribution highly depends on the water currents

MARINE FLORA

Common Name

Red Harpoon Weed

Scientific Name

Asparagopsis armata

Description

This species of marine red algae has two morphologically different stages: The gametophyte stage is pale purplish-red, while the tetrasporophyte stage is brownish-red, filamentous, and highly branched.

Habitat

Epiphytic to algae, especially Corallina spp.

depth

0-40m

Size

Up to 200 mm

Status according to ELNAIS

Alien – Casual

Pathway of Origin

Unaided

Origin

Native to western Australia, mechanism of spread unknown

first sighting in greek waters

Santorini, 1972

Impacts

Asparagopsis armata is noted for its high biomass production and biotechnological potential due to the myriad of produced secondary metabolites. However, it’s also one of the most aggressive invasive seaweed species, causing economic and ecological problems in Europe.

further information

The asexual phase of Asparagopsis armata was once described as a separate species, Falkenbergia rufolanosa.

Common Name

Red Sea Plume

Scientific Name

Asparagopsis taxiformis

Description

This species of red algae has a cosmopolitan distribution in tropical to warm temperate waters.

Habitat

Tropical/subtropical

depth

0-14m

Size

Between 5 to 20 cm

Status according to ELNAIS

Alien – Invasive

Pathway of Origin

Unaided

Origin

Native to southern Australia and New Zealand, mechanism of spread unknown

first sighting in greek waters

1992

Impacts

A.taxiformis erodes the habitat structure and biodiversity of native algal forests in the Mediterranean Sea. The seaweed has been shown to have a positive impact in methane reduction in livestock. Feeding ruminants a diet containing 0.2% A. taxiformis reduced their methane emissions by nearly 99%.

further information

Among 20 types of seaweed tested, A. taxiformis showed the most promise in reducing methane emissions in ruminants, with nearly 99% effectiveness

Common Name

Caulerpa spp. are commonly known as Sea Grapes

Scientific Name

Caulerpa cylindracea

Description

This green macroagae has one main stolon with coarse branchlike structures bearing clusters of miniature grapelike appendages.

Habitat

Colonises a variety of substrata from the intertidal zone to over 60 m in depth

depth

0-70m

Size

From 5 to 30 cm

Status according to ELNAIS

Alien – Invasive

Pathway of Origin

Unaided

Origin

Native to western Australia, mechanism of spread unknown

first sighting in greek waters

1993

Impacts

Caulerpa cylindracea is a key invasive species in the Mediterranean Sea where it has spread widely, raising ecological concerns. It dominating presence has been found to alter indigenous flora and fauna biodiversity, affect the behavior of native species and have adverse repercussions on fish growth and population dynamics.

further information

Caulerpa cylindracea has a unique reproductive strategy, reproducing vegetatively by fragmentation, and sexually through a process known as holocarpy, where the entire organism’s cytoplasm is used up in the creation of gametes.

Common Name

Fern algae

Scientific Name

Caulerpa scalpelliformis

Description

Delicate, fern structures creating fronds that resemble a comb, they are a bright, dark green.

Habitat

Tropical and subtropical distribution on rocky substrate, often in rock pools.

depth

0-30m

Size

20cm, with fronds around 3cm

status (ELNAIS)

Unknown

Pathway of Origin

Unknown

Origin

Native to western Australia, mechanism of spread unknown

Status according to ELNAIS

1929 (First Mediterranean sighting)

Impacts

Disrupting habitat and ecology of native species with preference for rock pool habitats.

further information

This species can control nutrient levels in the water by absorbing nitrates and phosphates, and are used in aquariums for this reason.

Common Name

Killer Algae

Scientific Name

Caulerpa taxifolia

Description

Caulerpa taxifolia is a light green macroalga with upright leaf/feather-like fronds arising from creeping stolons.

Habitat

This species can be found on a wide variety of substrates from rock, sand and mud to seagrasses. It is usually found in depths of 3-35m, but has been recorded at depths down to 100m in the Mediterranean.

depth

0-100m

Size

Frond diameter is 6-8mm and frond length is usually 3-15cm in the shallows, 40-60cm in deeper situations but can grow up to 2.8m in height

Status according to ELNAIS

Alien – Established

Pathway of Origin

Unaided

Origin

Native to tropical waters of populations naturally occurring in the Pacific Ocean, Indian Ocean and the Caribbean Sea, though not confirmed, its spread in the Mediterranean may be due to accidental release

first sighting in greek waters

2010

Impacts

This invasive species disrupts marine ecosystems by out-competing native species for food and light and due to the toxic effect of its caulerpenyne compounds. It forms large monospecific meadowns and vastly reduces biodiversity and suitable fish habitats. It can get caught and cause damage to fishing gear and accumulation of its toxins in fish populations can impact human consumption of local fish e.g. Mediterranean bream (Sarpa salpa).

further information

Caulerpa taxifolia has been cultivated for use in aquaria since the early 1970s in Western Europe. A cold-resistant clone was bred and later distributed to various aquaria, which eventually led to its escape into the wild and invasive behavior. It’s listed as one of the world’s 100 worst invasive species by the IUCN Invasive Species Specialist Group.

Common Name

Green Sea Fingers/Dead Man’s Fingers

Scientific Name

Codium fragile

Description

A siphonous green algae, it consists of one to several erect fronds with cylindrical, spongy branches and is attached to substrates by a spongy basal disc.

Habitat

Intertidal and shallow subtidal rocky bottoms and sheltered habitats such as harbours and bays.

depth

0-15m

Size

Typically 15 to 40 cm. Can grow up to 1 meter.

Status according to ELNAIS

Alien – Invasive

Pathway of Origin

Transport – Stowaway (angling, fishing equipment)

Origin

Native to the north Pacific Ocean and Japan, spread as a stowaway on transport vessels

first sighting in greek waters

1992

Impacts

This alga can displace native species such as Codium tomentosum. It’s a rapidly spreading invasive species in several regions, creating maintenance challenges for aquaculturists as it attaches to almost any hard surface in the subtidal zone. It can overgrow and smother shellfish beds, clog scallop dredges, foul fishing nets, reduce the amenity of jetties, beaches and wharf pilings and hinder the movement of fish and larger invertebrates.

further information

Codium fragile has been introduced as an invasive largely via shellfish aquaculture and attached to ship hulls. It has two subspecies that are similar in appearance but can be distinguished microscopically. One subspecies, Codium fragile subsp. atlanticum, arrived in the southwest of Ireland around 1808, spreading across Britain and other parts of Europe. Another subspecies, Codium fragile subsp. tomentosoides, is one of the most invasive seaweed species in the world, with extensive trans oceanic and inter-oceanic spread this past century.

Common Name

Sea whip

Scientific Name

Galaxaura rugosa

Description

Branching red algae with cylindrical branches that resemble a whip, often reddish/purple. Bushy growth form, often covered in a carbonate crust giving them a rough texture.

Habitat

Shallow areas with a lot of sunlight, attaching to coral reefs, rocky substrate, and occasionally the tubes of polychaete worms.

depth

0-10m

Size

Around 5cm

Status according to ELNAIS

Unknown

Pathway of Origin

Unknown

Origin

Tropical and subtropical seas of the Atlantic, Carribean and Gulf of Mexico, mechanism of spread unknown

first sighting in greek waters

1995

Impacts

Contributes heavily to protection of invertebrates in natural habitat and of nutrient recycling but may throw off the balance of nutrient cycling in habitats where it is invasive

further information

Currently being studied for their potential use in biotechnology and bioactive compounds for medicinal applications.

Common Name

Chalky weed

Scientific Name

Ganonema farinosum

Description

Deep red branching algae with coral like fronds that spread outwards in a tree-like formation

Habitat

Upper sublittoral zone

depth

0-10m

Size

20cm high

Status according to ELNAIS

Unknown

Pathway of Origin

Unknown

Origin

Native to South America, mechanism of spread unknown

first sighting in greek waters

1931

Impacts

Native biodiversity loss due to change in community structure and function

further information

Studies show that specimens of this species house the highest population density and largest body size of Caprellidae

Common Name

Broadleaf Seagrass

Scientific Name

Halophila stipulacea

Description

Rhizomes fixed to sand by roots, bearing pairs of leaves at regular intervals. Leaves have a serrated edge.

Habitat

Euryhaline with a wide ecological range, preference for warm water