scholarly journals Is the comb jelly really to blame for it all? Mnemiopsis leidyi and the ecological concerns about the Caspian Sea

2004 ◽  
Vol 269 ◽  
pp. 173-183 ◽  
Author(s):  
M Bilio ◽  
U Niermann
Keyword(s):  
Caspian Sea ◽  
Mnemiopsis Leidyi ◽  
The Caspian Sea ◽  
Comb Jelly

scholarly journals The biology and abundance of kilka (Clupeonella spp.) along the coast of Azerbaijan, Caspian Sea

2006 ◽  
Vol 63 (9) ◽  
pp. 1665-1673 ◽  
Author(s):  
Elchin V. Mamedov
Keyword(s):  
Caspian Sea ◽  
Ecosystem Functioning ◽  
Mnemiopsis Leidyi ◽  
The Caspian Sea ◽  
Age Composition ◽  
Environmental Preferences ◽  
Total Allowable Catch ◽  
Comb Jelly ◽  
Commercial Species ◽  
Accidental Introduction

Abstract In the changing environmental conditions of the Caspian Sea, and specifically following the accidental introduction of the comb jelly Mnemiopsis leidyi from the Azov–Black Sea basin in the late 1990s, ecosystem functioning has been disturbed, particularly in the pelagic zone. The main commercial species of kilka in the Caspian, anchovy kilka (Clupeonella engrauliformis), suffered greatly from the introduction. The catch of kilka by Russia, Azerbaijan, and Iran dropped from 182 700 t in 2000 to 74 700 t in 2001, although the total allowable catch remained at 300 000 t. Between 2000 and 2004, the catch by Azerbaijan alone dropped from 18 500 t to 5 100 t. Recruitment of anchovy kilka failed in early 2001, resulting in an increase in the average age of the stock, and a big decline in abundance. During kilka surveys conducted in summer 2003 and summer 2004 along the Azerbaijan coast of the central Caspian, the average cone-net catch varied from 19.8 kg to 30.5 kg at depths of 51–90 m, and along the Azerbaijan coast of the southern Caspian from 6.1 to 33.7 kg at depths of 53–81 m. Information is provided on the biology and apparent environmental preferences of the three kilka species of the Caspian, specifically their age composition, growth rate, and mean weight, off the coast of Azerbaijan.

scholarly journals Effects of the Invasive Ctenophore Species, Mnemiopsis Leidyi, on the Caspian Sea

2013 ◽  
Vol 15 (1) ◽  
pp. 117-126
Author(s):  
Zahra Khoshnood ◽  
Reza Khoshnood ◽  
Mehdi Ghobeitihasab
Keyword(s):  
Invasive Species ◽  
Coastal Waters ◽  
Caspian Sea ◽  
Habitat Destruction ◽  
Significant Decline ◽  
Ecological Impacts ◽  
Economic Losses ◽  
Mnemiopsis Leidyi ◽  
The Caspian Sea ◽  
Wide Range

ABSTRACT Human interventions on the Earth’s natural systems are evident even in remote regions of the Antarctic and rain forests deep within the Amazon. In addition to human-induced climate change and habitat destruction, an emerging anthropogenic threat to biodiversity is the drastic species re-distribution (the movement of species from one place to another due to human intervention) at a global scale. This creates fertile conditions for biological invasions which in turn cause substantial economic and ecological losses. These human-mediated invasions, often referred to as “biological pollution”, are a worldwide problem that is increasing in frequency and magnitude, causing significant damage to the environment, economy and human health. Bioinvasions have strong impact on biodiversity and ecosystem functioning and stability. They are ranked as the second most important threat to biodiversity (after habitat destruction) by the World Conservation Union. The Ctenophore, Mnemiopsis leidyi, is one of the invasive species that naturally lives in the Atlantic coastal waters of North America and South America, but discovered in Azov, Black, Caspian, North, Baltic and Mediterranean (north-eastern part) seas in early 1980s. It seems that the main factor of its redistribution was the ballast waters of ships. As an alien species, Mnemiopsis leidyi caused many alterations in the Caspian Sea ecosystems. The fact that it feeds on the eggs of native fish Clopeonella spp., has resulted in a significant decline of its population; Clopeonella spp. were the main source of industrial fishing in the Caspian Sea and also the main source of food for precious fish species, the sturgeons, and therefore, their decline has caused a huge economical loss for the area's inhabitants and a significant decline of sturgeon populations. This species has caused massive ecosystem changes and substantial economic losses in the late 1980s-1990s, and it has been recognized as a problem of main ecological concern for the sustainable development of the region, together with the high level of anthropogenic pressures on the Caspian Sea ecosystems. Some special characteristics of this species, such as adaptation to a wide range of salinity and temperature, high capability of reproduction, hermaphroditism and dissogeny, have led to huge increases of its mass, especially in southern regions of the Caspian Sea, the coastal waters of Iran. In addition, it has become clear that this species does not have any natural predators in the Caspian Sea, and also that it can feed on any organisms smaller than itself in size. Owing to these facts, it is a huge ecological threat for the Caspian Sea ecosystems. The aim of the present paper is to review the biological and ecological impacts of this invasive species on the Caspian Sea ecosystems.

Integrated fisheries assessment and possible causes for the collapse of anchovy kilka in the Caspian Sea

2007 ◽  
Vol 64 (3) ◽  
pp. 503-511 ◽  
Author(s):  
Georgi M. Daskalov ◽  
Elchin V. Mamedov
Keyword(s):  
Caspian Sea ◽  
Abundant Species ◽  
Mnemiopsis Leidyi ◽  
Fishing Mortality ◽  
The Caspian Sea ◽  
Commercial Catch ◽  
Recruitment Failure ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Stock Collapse

Abstract Daskalov, G. M., and Mamedov, E. V. 2007. Integrated fisheries assessment and possible causes for the collapse of anchovy kilka in the Caspian Sea. – ICES Journal of Marine Science, 64: 503–511. Anchovy kilka (Clupeonella engrauliformis) is the most abundant species of fish in the Caspian Sea. An integrated catch-at-age analysis based on commercial catch data and relative abundance indices from research surveys over the period 1991–2004 indicated two main periods. First, a period of high catches, from 1991 to 2000, sustained by relatively good recruitment and high spawning-stock biomass. At the end of this period, catches peaked at up to 271 400 t, fishing mortality reached 1.8 y−1 in 1999, and overfishing seems to have taken place. Over the next period, 2001–2004, the stock virtually collapsed, recruitment failing in 2001 and remaining very low thereafter. In 2005, total catches dropped to a historical minimum of 54 300 t. The most likely primary cause of the stock collapse is the invasion and spread of the ctenophore Mnemiopsis leidyi in the Caspian Sea. The dramatic recruitment failure from 2001 to 2004 is primarily attributed to competition/predation by this ctenophore, although other factors, including overfishing, likely contributed.

Biodiversity, distribution and abundance of zooplankton in the Iranian waters of the Caspian Sea off Anzali during 1996–2010

2013 ◽  
Vol 94 (1) ◽  
pp. 129-140 ◽  
Author(s):  
Siamak Bagheri ◽  
Ulrich Niermann ◽  
Mashhor Mansor ◽  
Foong Swee Yeok
Keyword(s):  
Endemic Species ◽  
Caspian Sea ◽  
Native Species ◽  
Zooplankton Community ◽  
Heavy Rain ◽  
Mnemiopsis Leidyi ◽  
Hediste Diversicolor ◽  
The Caspian Sea ◽  
Weather Patterns ◽  
Invader Species

The mesozooplankton of the south-western Caspian Sea, off Anzali, sampled from 1996–2010, had undergone severe changes, especially after the year 2001, when the invasive ctenophore Mnemiopsis leidyi bloomed for the first time. Native species vanished or decreased, while invasive species such as Pleopis polyphemoides, Acartia tonsa, M. leidyi and the larvae of Balanus sp., plus Hediste diversicolor dominated the zooplankton. It could be stated that the increasing amount of nutrients since the early 1980s led to a decrease of endemic species and smoothed the way for opportunistic invader species, which outcompeted and depleted the endemic species in their turn. However, the major changes in the zooplankton community and possibly the blooming of M. leidyi during 2001–2002 were triggered by changing weather patterns, when a period with heavy rain at the end of the 1990s was followed by a prolonged drought (2001–2002). It is not clear to what extent M. leidyi was responsible for the disappearance of endemic Copepoda and Cladocera species such as Eurytemora grimmi, Limnocalanus grimaldii, Cercopagis pengoi, and Polyphemus exiguous, because the mesozooplantic invader species seemed to be more successful competitors than the endemic Caspian Sea fauna. Compared with other areas of the Caspian Sea, the development of the M. leidyi stock was moderate in the area under investigation. Mnemiopsis leidyi numbers and biomass increased from the beginning of sampling in 2001 to about 600 n.m−3 and 40–60 g wet weight m−3 until 2003. Since then the stock oscillated in this range until 2010.

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