Lessepsian migrant

RandallÕs threadfin bream, Nemipterus randalli, first recorded in Iskenderun Bay in Turkey in 2008, seems to have increased in the region. The species, widespread in the western Indian Ocean and with a rapid expansion, appears to have migrated to the bay via the Red Sea. Although its presence in the region has been published, there has been little or no information as to age and growth parameters of this Lessepsian migrant in its new habitat. The present study aims to determine the basic age and growth parameters of the species colonized in the region. A total of 379 collected individuals were studied from November 2007 to October 2008. Total specimen lengths ranged from 4.80 to 21.50 cm, and weights from 1.10 to 138.36 g. Maximum age was 3 years for both sexes. The length-weight relationship was described as W = 0.0011 · L 3.061 (r 2 = 0.982). The von Bertalanffy growth parameters were: L ¥ = 34.96 cm; K = 0.214 year )1 ; t 0 = )1.244 year for the entire population. These data were compared with results from studies made in other geographic areas.

The upside-down jellyfish—Cassiopea andromeda (Forsskål, 1775)—is considered an established alien within the eastern Mediterranean Sea, but the species exhibits a highly sporadic occurrence further west within the basin. This study reports the second documented bloom of the species within coastal waters in the Maltese Islands and the third bloom of the species in the westernmost part of the eastern Mediterranean, a full nine years after its first appearance in this part of the Mediterranean.

Last few years, a seaweed unlike any other, Caulerpa taxifolia has been spreading in the North-West Mediterranean. Gradually, richly colored and varied Mediterranean populations are being replaced by the uniform fluorescent green landscape of the Caulerpa taxifolia meadows. Accidentally introduced into the sea in Monaco in 1984, the green seaweed Caulerpa taxifolia spread rapidly along the Mediterranean coast. There are already 5 five countries that are affected (after Monaco, France in 1990, Italy and Spain in 1992, and Croatia in 1994) and more than 3000 hectares already colonized. It possesses certain unique characteristics (resistance to the cold, gigantism, vigour of development, density, ecological dominance, etc.) that have never before been observed in tropical populations of this kind or in other seaweed introduced into the Mediterranean. In situ investigations are carried out with SCUBA techniques to obtain detailed map of contaminated zones of Caulerpa taxifolia. All the stable substrates (rock, sand, silt, Posidonia meadows) can be colonized. All types of bottom, especially from 3 to 50m, can be invaded. Caulerpa taxifolia has been observed in summer, alive and well established, though in lower density, as deep as -99m. Although more discreet in winter, Caulerpa taxifolia never altogether disappears: it can survive for a few days at 7C and for 3 months at 10C. It starts growing again when the water rises above 15C. It is to be found both in good quality water and in polluted harbors, on rocky headlands exposed to waves and in sheltered bays. Also Caulerpa racemosa, which is currently colonized the Mediterranean, may present different characteristics from one region to another the specimens described in the same region at the beginning of the 20th century. Like Caulerpa taxifolia, Caulerpa racemosa colonizes all types of substrate such as rock, sand, mud and dead Posidonia meadows down to 60m depth and interferes with marine coastal biocenoses. The expansion of Caulerpa racemosa may alter marine habitats.

Because of the above description reasons, there are laws and guidelines (that have been adapted by France and Spain and by international organizations) banning or recommending against the harvesting, sale or transportation of Caulerpa taxifolia. In this study, the warning of public and alarming of authorities for the ecological and toxicological effects of invasive seaweed by means of the Turkish newspapers, magazines, televisions are described. Detailed information materials for Caulerpa taxifolia and also for Caulerpa racemosa are explained.

Caulerpa racemosa is a tropical species widely distributed throughout the world that immigrated to the Mediterranean from the Red Sea via Suez Channel. Since the beginning of the 20th century, the tropical seaweed Caulerpa racemosa, which is known as a lessepsian migrant, has been observed also in the Mediterranean Sea. But it became an invasive species in the Mediterranean since the early ‘90. Although it had always been considered a rare species, in last six years Caulerpa racemosa is particularly colonizing in the Aegean and Mediterranean Sea of Turkish region. In situ observations are still carried out and described the characteristics of this seaweed by Ş.Cirik and coworkers . In this study, the observations and determinations of Caulerpa racemosa (Forsskål) J. Agardh in Mersincik Island and Yediadalar sections of Gökova Bay, also in Kargı Island-Akyarlar, Karaincir Beach, Kargı Beach, Gümüşlük, Aspat sections of Bodrum, in Marmaris (between Aegean Sea and Mediterranean) and in Güzelçamlık section of Kuşadası, in Çeşme (Aegean Sea) are reported. Several SCUBA diving techniques are carried out by scientific divers down to 60 meter depths for in situ observations and mapping. The characteristics of this alga and its habitat are described. It was observed that Caulerpa racemosa is progressing to the northern Aegean coast of Turkey.

RandallÕs threadfin bream, Nemipterus randalli, first recorded in Iskenderun Bay in Turkey in 2008, seems to have increased in the region. The species, widespread in the western Indian Ocean and with a rapid expansion, appears to have migrated to the bay via the Red Sea. Although its presence in the region has been published, there has been little or no information as to age and growth parameters of this Lessepsian migrant in its new habitat. The present study aims to determine the basic age and growth parameters of the species colonized in the region. A total of 379 collected individuals were studied from November 2007 to October 2008. Total specimen lengths ranged from 4.80 to 21.50 cm, and weights from 1.10 to 138.36 g. Maximum age was 3 years for both sexes. The length-weight relationship was described as W = 0.0011 • L 3.061 (r 2 = 0.982). The von Bertalanffy growth parameters were: L ¥ = 34.96 cm; K = 0.214 year)1 ; t 0 =)1.244 year for the entire population. These data were compared with results from studies made in other geographic areas.