Abstract: Indigenous freshwater crayfish (ICS) are important biodiversity components and desirable fishery targets. However, populations are increasingly stressed by various anthropogenic impacts. Moreover, both established populations of non-indigenous crayfish species (NICS) and new 'waves' of introductions exert significant pressure to indigenous species on a Pan-European level, through direct competition for space and resources and, in the case of North American species, as vectors of crayfish 'plague'. In this context, serious risks exist from conventional and internet-based aquarium trade and particularly from deliberate or accidental releases, given the fact that public knowledge on this issue is practically negligible. Therefore, during 2011, a survey for freshwater crayfish was conducted in eleven large-size pet shops located in three major cities and in three large internet-based companies in Greece. Overall, eight species belonging to three genera (Procambarus, Cherax and Cambarellus) were recorded, originating from the USA, Australia, New Guinea and Mexico. The three most popular species were assessed by the Freshwater Invertebrate Invasiveness Scoring Kit (FI-ISK) for their invasion potential and two of them were indicated as 'high-very high risk' species. Accordingly, the ornamental trade of NICS in Greece needs to be urgently controlled and a framework for protecting ICS is therefore discussed.
Abstract: Non-indigenous freshwater crayfish species (NICS) outnumber the indigenous ones in many European countries, representing a major threat to biodiversity via the spread of crayfish ‘plague’ and aggressive invasion and antagonism performance. Although the biological basis of this situation is well studied, the possible role of social, economic and demographic factors on this situation has been ignored. In an attempt to explore such relationships, we suggest that human population density and economic growth (measured as gross domestic product (GDP) per capita) are positively related to the increased number of NICS in the EU area. Moreover, this pattern is evident in countries with higher overall footprint (i.e. the human demand of biologically productive land and sea in global hectares required to provide resources and services on waste assimilation) compared to biocapacity. Within the above context, actions are urgently needed to restore/balance existing and projected metabolic rifts (i.e. ruptures in the normal metabolic processes in natural systems) created by the presence of NICS.
Abstract: This paper presents records extending or confirming the distribution of Mediterranean species. Three alien algae are included,
namely Codium taylorii reported for the first time from the Aegean and Turkey (Izmir Gulf), Caulerpa racemosa var. cylindracea
(Karpathos and Chalki Isl., Aegean Sea) and Ganonema farinosum (Karpathos Isl., Aegean Sea). As far as animals are concerned,
Litarachna divergens (Acari: Hydrachnidia) was recorded (Side, Eastern Mediterranean) and represents a new amendment at genus
level for Turkish fauna. Other invertebrates include alien species such as the crabs Dyspanopeus sayi (Lago Fusaro, SW Italy),
Percnon gibbesi (Larnaca, Cyprus; Karpathos and Chalki Isl., Aegean Sea) and Callinectes sapidus (Voda estuary, NW Greece),
the nudibranch Aplysia dactylomela (Boka Kotorska Bay, Montenegro), the gastropod Conomurex persicus (Karpathos and Chalki
Isl., Aegean Sea) and the bryozoan Electra tenella (Livorno harbour and Messina Straits area). The alien fish Siganus luridus,
Siganus rivulatus, Fistularia commersonii, Sphyraena chrysotaenia and Sargocentron rubrum are also reported from the islands
of Karpathos and Chalki, and Pteragogus pelycus from Heraklion Bay, Crete. In addition, new localities for four rare Mediterranean
inhabitants are given: the cephalopod Thysanoteuthis rhombus (NW Sardinia) and the fish: Lampris guttatus (Calabria, S
Italy), Petromyzon marinus (Gokova Bay) and Remora australis (Saronikos Gulf), while the opisthobranch gastropod Cerberilla
bernadettae is reported for the first time from the E Mediterranean (Cyprus). Finally, three species of the Aegean ascidiofauna are
recorded for the first time: Lissoclinum perforatum, Ciona roulei and Ecteinascidia turbinata. Furthermore, it was established that
Phallusia nigra has extended its distributional range to the north of the Aegean Sea.
Abstract: The present work reports on the extended distribution of nineteen species in the Mediterranean. These are: Upeneus pori
(Fish:Turkey), Bursatella leachii (Mollusca, Opisthobranchia: eastern coast of Spain), Sparisoma cretense (Fish: Ionian coast
of Greece), Pseudobryopsis myura (Chlorophyta:Turkey), Aplysia dactylomela (Mollusca, Opisthobranchia: Karpathos island,
and Kyklades Archipelago, Greece), Asparagopsis armata and Botryocladia madagascariensis (Rhodophyta: South Peloponnesos,
Greece), Oxynotus centrina (Fish: Greece), Caulerpa racemosa var. cylindracea (Chlorophyta ), Stypopodium schimperi
(Phaeophyta ) Siganus luridus and Stephanolepis diaspros (Fish) Percnon gibbesi (Decapoda, Brachyura) (Kyklades Archipelago,
Greece), Cerithium scabridum (Mollusca, Prosobranchia: Anavissos: Greece) and Cerithium renovatum (Mollusca, Prosobranchia:
N. Κriti), Cassiopea andromeda (Scyphomedusa: Rhodos Island, Greece), Abra tenuis (Mollusca Bivalvia: Vouliagmeni
Lake, Greece) Lagocephalus lagocephalus (Fish: Calabrian coast, Italy) and Plocamopherus ocellatus (Mollusca, Opisthobranchia:
Ä°skenderun Bay, Turkey).
Abstract: Ichthyofauna in the Hellenic freshwaters is quite diverse consisted of 161 species (including 28 non-natives), out of the 546 native species in Pan-European level. However, the status of many aquatic ecosystems is currently degraded as a result of a variety of anthropogenic impacts. This has direct reflection on the conservation status of the indigenous and native fish species whose populations are in many cases declining in favor of the invasive ones. Prussian carp (Carassius gibelio ) is probably the most dominant invasive species and currently is considered as naturalized in about 26 lake and river basins. Its successful adaptation and proliferation is mainly attributed to its dual reproductive mode (allogynogenetic and gonochoristic), the opportunistic-omnivorous feeding habits and the ability to withstand and flourish in adverse ecological conditions. Accordingly, it exerts competitive, as well as destructive effects upon the indigenous fish species (sperm parasitism, antagonism for food, spawning grounds and spawning substrates) and therefore, efforts are needed to sustain a relative balance of the populations. This review aims to critically discuss the status of C. gibelio in Greece, the intrinsic causes of establishment and the observed impacts on ecosystems. Finally, reasonable actions are proposed related to exploitation of C. gibelio stocks and a path model for the protection of native fish species and their ecosystems.
Abstract: Aquaponic systems aim to exploit the advantages of aquaculture and hydroponic systems. A reasonable fish production can be sustained and at the same time a wide range of green plants and vegetables will be beneffited from the nutrient-rich outflow of the fish tanks, providing nitrification services to reduce the ammonia and nitrite loads. In this paper, the performance of a small-scale modular aquaponic system was assessed for the critical initial running period of 14 days during
September 2011, using lettuce, basil and Nile tilapia. It was evident from the results that mid-range fish stocking densities and accordingly nutrient loads are able to support a plant harvest at a ratio of 1:4 to 1:5 (amount of fish feed provided: harvestable biomass) in both species, depending on the initial size of the plants. Very small plants with sensitive root system should be avoided, as well as increased ammonia loads. Further improvements could be achieved by fine-tunning of the flow characteristics of the system, the standardization of water quality profile, the appropriate selection of substrate and the addition of extra biofiltration compartment.
Abstract: Sex control in aquaculture aims to benefit from desirable traits expressed differentially by each sex. In ornamental fish, such manipulation can be profitable, especially in species with high price discrepancy between sexes. This is particularly true for the fancy males of Siamese fighting fish (Betta splendens Regan, 1910), which are very popular aquarium pets. Therefore, fry originating from controlled reproduction were fed initially with artemia nauplii from day 4 post-hatch up to day 7 post-hatch. Subsequently, they were orally administered with 17α-methyltestosterone (MT) (via inert feed) in four concentrations (1, 2, 3 39 and 4 mg/kg of hormone in feed) for eight weeks. The experiment was repeated with fry of the same origin in identical conditions with the exception of a prolonged supply period (from day 4 post-hatch until day 11 post-hatch) of artemia nauplii enriched with red pepper. The results demonstrated that the 3 & 4 mg/kg doses resulted in 100% masculinisation and the extended provision period of enriched artemia nauplii increased the survival rate of the offspring; however, mortality rate was increased in all hormonally treated groups in both experiments, partly due to the prolonged hormone administration period. Conclusively, oral administration of low ΜΤ doses is effective for the masculinization of Siamese fighting fish.
Abstract: The present essay attempts to address the observed complex crisis of aquaculture and fisheries sectors within the broader context of global crisis, using examples of significant negative effects on natural and social environment. At the same time the underlying causes of the sectors’ crisis are viewed under the lens of metabolic rift theory, applied to shrimp farming, glass eel trade and tuna fishing and farming for sushi. Current crisis in the Greek aquaculture sector is briefly reviewed as a representative example of aquaculture developmental process in western societies, followed by an attempt to address the emergence of organic aquaculture schemes. Finally, eco-sound directions and polices in aquaculture development are briefly discussed, in order to minimize environmental effects, social inequity and partially restore existing metabolic rifts.
Abstract: Organic aquaculture has recently attracted attention from both researchers and the industry. Organically produced aquatic products are increasingly available to the consumers and particularly sea bass and sea bream from certified farms in Greece have been exported and also channelled to large retail markets in Greece since 2008. The current paper briefly reviews issues pertaining to global organic aquaculture and national organic and conventional aquaculture production with special focus on organic sea bass and sea bream production. Finally, future prospects and challenges are discussed in a wider context, with regard to environmental sustainability, markets and further development of organic aquaculture.
Abstract: The diversity of ichthyofauna in the Hellenic freshwaters is highlighted by the presence of 161 species. This actually represents 27.8% of the total fish species recorded in the European freshwaters, including both native and introduced, suggesting that Greece represents a ‘hot spot’ for biodiversity. The introduction of alien species for restocking, aquarium trade and aquaculture was responsible for deliberate or accidental releases of alien specimens in the open waters and in some cases for establishing populations. On the other hand, commercially valuable alien species (for example salmonids, cyprinids and lately sturgeons) generated significant income to individuals, companies and to the national economy. The current work aims to review the situation regarding the presence of alien fish and crayfish species in the Hellenic freshwaters and particularly in aquaculture and to stress out issues concerning their aquaculture potential.
Abstract: Some fish species exhibit a biochemical response to low winter temperatures. For example, after a period of cold acclimation, an increase in enzyme activity occurs. This can result in at least partial compensation in the rate of biochemical reactions of aerobic metabolism. Sea bass (Dicentrarchus labrax L. 1758) is a commercially important fish for the Mediterranean mariculture industry, which can grow satisfactory in both freshwater (FW) and seawater (SW) conditions. The purpose of the present work was to evaluate the survival and growth of sea bass in FW earthen ponds. The experiment was initiated in September 2003 in order to avoid the water temperature highs during spring–summer and allow several weeks for acclimation before the winter temperature lows. Fish growth occurred for several months, but by the end of December 2003, ambient water temperature reached levels below 5uC and mass mortality occurred. The capacity of sea bass for thermal compensation was evaluated by monitoring the activity of cytochrome c oxidase (CCO) of red axial muscle.
The activity of CCO initially increased from 6.4 (¡0.98) in September (ambient water temperature 19uC) to 10.4 (¡1.49) in October (ambient temperature 15.4uC), but decreased again to 8.8 (¡1.45) in November (ambient temperature 12.3uC). A similar trend was exhibited by the glycolytic enzyme lactate dehydrogenase in white muscle. The results do not indicate a capacity of thermal acclimation in FW ponds with low temperature (,13uC) for sea bass. Evidently, seasonally extremely low temperature is a challenge for the production of sea bass.
Abstract: The purpose of this work was to investigate the size-relative effectiveness of clove oil as an anaesthetic for rainbow trout and goldfish. In total, 128 rainbow trout (Oncorhynchus mykiss) (two groups of 20-23 and 30-33 cm mean fork length) and 160 goldfish (Carassius auratus) (four size groups of 1.5-2.5, 5-7, 11-15 and 20-25 cm) were anaesthetized at different clove oil concentrations of 50, 100, 150 mg·l-1 for trouts and 75, 100, 150 mg·l-1 for goldfish. Rainbow trout exhibited total loss of balance and no response to external stimuli with shorter induction time as dosage increased (120.5 s, 64.4 s and 44.3 s, respectively). Goldfish exhibited total loss of balance and no response to external stimuli after induction time that varied with dosage used and body size of fish. The small fish (1.5-7 cm) exhibited shorter induction time which ranged from 84.28 s at 75 mg·l-1 clove oil to 41.14 s at 150 mg·l-1 clove oil. The larger fish had a longer induction time inversely related to the dosage. Recovery time was longer than induction time in both species. Both species recovered within 6 min after anaesthesia at 150 mg·l-1 clove oil. Clove oil did not produce marked changes (P < 0.05) in the physiological indicators of goldfish compared to the control. However, marked changes (P < 0.05) were exhibited in the haematocrit
of treated rainbow trout that also exhibited hyperkalaemia and hyperglycaemia (P > 0.05). For both fish species, clove oil was effective, producing minimum stress and zero mortalities, and can be recommended as an effective anaesthetic.
Abstract: The Hellenic freshwater aquaculture sector is dominated by the alien rainbow trout from the early 1950s’. This species actually represented 96.5% of the total inland production during 2007. Other groups of species accounted for minor production volumes and apart from common carp, most of them are of alien origin as well. Therefore, absence of production diversification, the presence of alien species which in some cases have seriously impacted aquatic biodiversity and the emerging consumer sensitivity towards environmentally-friendly practises require thorough re-assessment of native species with promising aquaculture potential. This trend is particularly evident in Eastern Europe and Asia, were native species (particularly cyprinids) outcompete the aliens. The current review aims to present past and present farming efforts on native fish and crayfish species in Greece which collectively belong to six families, and to discuss future development prospects.
Abstract: In order to assess the current status of the critically endangered Valencia letourneuxi in Kalamas River basin, an extensive field survey including twelve sampling stations was undertaken using back-pack electrofishing device, D-shaped frame net and small mesh size nets in October 2008. In total, 552 fish specimens were collected, belonging to ten freshwater fish species, plus mullets (collectively
grouped as Mugil spp.). V. letourneuxi was found at one station (Anakoli ditch) (8.3% of sampling stations), at very low relative density (0.95%), where it co-occurred with the loach Cobitis hellenica, the goby Economidichthys pygmaeus and the introduced Eastern mosquitofish Gambusia holbrooki, with the last at very high relative densities. Moreover, water samples from selected stations were
phasmatophotometrically analysed for ÎΗ3-Î, ÎΗ3, ÎΗ4, ÎΟ2-Î, ÎΟ2, ÎaÎΟ2, NO3-N, NO3, PO4, P and P2O5. Overall, V. letourneuxi was extirpated from one of its two previously known populations in this basin and its single surviving population was characterized by low local relative density and steep decline in relation to recent records (2005). Moreover, the presence at very high densities of the G. holbrooki as well as the increased eutrophication (due to high ammonia and phosphorus inputs) in its highly modified habitat, suggest a rapid population collapse with significant risk of extirpation from Kalamas basin in the near future. The necessary conservation measures are outlined.
Abstract: Dolphin therapy emerged during the 1950s. The work of Dr. John Lilly played an important role, since he investigated the impact of dolphins on disabled people. From 1978 onwards, the therapeutic aid of dolphins was further advanced, especially after the success of Dr Davis Nathanson with Down-syndrome children and Dr. Ludmila Lukina, who developed many therapeutic methods. The therapeutic method is based on the hypersonic stimulus transmitted by the dolphin sonar (a strong organ at the top of the head, which helps dolphins to produce and receive sounds) towards the central nervous system of humans, resulting in the synchronization of brain hemispheres for a certain period (brain waves are concerted in both hemispheres regarding frequency and phase), which is in turn contemplated as neurologically uncommon. The scientific experience of supplementary therapeutic approaches using dolphins reinforces the classical medical therapies and has provided solid proofs of positive effects of such programmes on: autism, Rett syndrome, Down syndrome, mental delay, brain paralysis, depression, cognitive difficulties, hyperkinetic syndrome. Therapeutic centres, such as Dolphin Assisted Therapy, provide various therapeutic programs of different duration, targeting to assist people with a variety of problems. Scientific results documented that dolphins affect the speech during interaction with humans, decrease the depression symptoms and reduce the pain in people suffering from multiple sclerosis.
The present work provides up to date data regarding dolphin therapy in a worldwide context. It is actually a thorough literature review, which attempts to cover a gap in the field of therapeutic contribution of animals to human's health.
Abstract: In the past, sturgeons were practically unknown in Greece,
both to the public and to scientists, the latter not having had
the opportunity to study wild populations of the four native
species. Populations of stellate sturgeon (Acipenser stellatus
Pallas, 1771), Adriatic sturgeon (Acipenser naccarii Bonaparte,
1836), and beluga sturgeon (Huso huso L., 1758) gradually
collapsed by the end of the 1970s. Only the River Evros
(Thrace, N.W. Greece) sustained a small fishery and caviar
canning operation with European sturgeon (A. sturio L., 1758)
until 1975. Collapse of stocks was mainly attributed to
overfishing, pollution and damming. Sturgeons became widely
known after initial farming efforts by the Municipal Hatchery
at Lake Ioannina in 1992. Broodstock or fertilized eggs of
species with high aquaculture potential, such as sterlet
(Acipenser ruthenus L., 1758), Russian sturgeon (Acipenser
gueldenstaedtii Brandt, 1833), bester hybrid (A. ruthenus ·
H. huso), paddlefish (Polyodon spathula Walbaum, 1792),
Siberian sturgeon (Acipenser baerii Brandt, 1869) and white
sturgeon (Acipenser transmontanus Richardson, 1836) were
imported into Greece between 1992 and 2004. Hatchery
technology, larval rearing and production systems are
reviewed in this paper and, despite problems, past and present
efforts appear to meet a particular interest of the aquaculture
sector as well as of those interested in the restoration of wild
stocks.
Abstract: Background. The usage of common carp pituitaries has been associated with very high costs, resulting from sacrificing the valuable broodstock. A close taxonomic proximity between the Common carp, Cyprinus carpio L.,
and Prussian carp, Carassius gibelio (Bloch, 1782), reflected in the presence of high levels of the homologous
carp LH hormone in Prussian carp pituitaries, was recently demonstrated. This prompted the present authors to
evaluate the Prussian carp pituitaries as a less expensive alternative to carp pituitaries, for inducing spawning in
common carp.
Materials and Methods. Prussian carp were fished in Lake Pamvotis (NW Greece) on April 4, 2007 and 204
pituitaries were extracted and processed. Accordingly, the prepared pituitary liquid extract was injected in 30
female common carp (experimental group) in the State Carp Hatchery in Psathotopi, (western Greece). Common
carp pituitary extract was used for the hypophysation of female common carp in the control group (n = 30). In
both groups, standard hatchery procedures were followed concerning broodstock handling during the artificial
propagation of common carp. Fertilized eggs were incubated in 7-L Zugar jars after removing the sticky substrate
and hatching percentage was calculated.
Results. Spawning success was 73.3%, total egg yield was 5.94 kg, total relative fecundity was 112.5 g · kg–1
of body weight (150.0 g · kg–1 of body weight based on fertile broodstock), and hatching percentage reached
85.2 %. Statistically, all the above performance values were not significantly different compared to the controls.
Conclusion. Taking advantage of a natural resource practically unexploited, the use of Prussian carp pituitaries
in the artificial propagation of common carp was equally effective to common carp pituitaries, contributing to
lower running costs in the hatchery.
Abstract: The narrow-clawed crayfish Astacus leptodactylus Eschscholtz, 1823, is widely
distributed in eastern European and western Asian countries. However, species presence
in Greece was documented only by limited museum conserved specimens dating back to
1893. Recently (May 2005) several crayfish were captured in the Evros River (close to city
of Didimotiho) and these were identified as A. leptodactylus. The present work confirms
the presence of A. leptodactylus in the Evros River still hundred and twelve years later and
introduces the possibility of A. leptodactylus being indigenous to Greece.
Abstract: Gibel carp (Carassius gibelio Bloch, 1782) is regarded as a pest species in most aquatic ecosystems
where it occurs and eradication methods have not been very promising. However, because
of the close taxonomical proximity between gibel carp and cultured cyprinids, the pituitary of
gibel carps could be exploited for hormonal induction of artificial propagation in aquaculture.
Thirty-two mature female gibel carps were electrofished in Lake Pamvotis (northwest Greece) in
March 2005 and their pituitaries were collected and processed. The carp luteinizing hormone
(cLH) levels in 20 pituitaries were assayed and found to correlate with total body weight, total
length, dry pituitary weight, and gonadosomatic index. The cLH levels were in the same range
as cLH levels in pituitaries of common carp (Cyprinus carpio Linnaeus, 1758) used in Israeli
hatcheries for artificial propagation. Hence, it may be possible to use gibel carp pituitaries for
hormonal induction in cyprinids, with total weight of the gibel carp as a field criterion for selecting
pituitary donors.
Abstract: Specimens of the three known Greek crayfish species, Astacus astacus (Linnaeus,
1758), Astacus leptodactylus Eschscholtz, 1823 and Austropotamobius torrentium
(Schrank, 1803), were collected from seven localities in Greece and were examined for
the epibionts of Branchiobdella sp. (Annelida: Clitellata) and the aelosomatid Hystricosoma
chappuisi Michaelsen, 1926 and the copepod Nitocrella divaricata (Chappuis, 1923). As a
result, three branchiobdellid species, Branchiobdella parasita (Braun, 1805), Branchiobdella
pentodonta Whitman, 1882 and Branchiobdella hexodonta Grüber, 1883 were found. This
was also the first report of B. pentodonta from Greece as well as H. chappuisi, the latter
being found on crayfish gills in one of the localities investigated. Moreover, the current
work represents the first documentation of the presence of B. parasita and B. hexodonta
in several localities in Greece.
Abstract: Freshwater crayfish are found in 20 out of 53 Prefectures of Greece (38%) and
they form isolated populations in relatively pristine water bodies. Three indigenous
crayfish species (ICS) occur in Greek waters: Astacus astacus, Astacus leptodactylus
and Austropotamobius torrentium, as well as one non-indigenous crayfish species
(NICS) Pacifastacus leniusculus. Greece represents probably the most southern natural
distribution limit for A. astacus and A. torrentium in the world. Concerning NICS,
P. leniusculus was imported, at least in two cases, from Sweden and Germany during
the early and late 1980’s respectively, in order to replace A. astacus stocks impoverished
by human activities. Recently, Cherax quadricarinatus specimens have been seen in a
restaurant’s aquarium and pet shop, raising fears about uncontrolled imports of alien pet
species. During our 2004-2005 survey, we found that P. leniusculus established not only
a thriving population in the artificial Lake Agra (Region of Central Macedonia), but also
they co-occur with A. torrentium there. It is also suspected that A. astacus may co-occur
there with these two species, as three large male specimens of A. astacus were caught in
a creek close to the lake. Concerning A. leptodactylus, there are three sets of preserved
samples from the River Evros (state border with Turkey in Thrace today), dated back to the
19th century, but no recent information about occurrence was available. But the accidental
catch of six specimens of A. leptodactylus during May 2005 in that river re-documented
the occurrence of the species. Finally, a deep-dwelling A. torrentium population with
bluish legs was found to live in depths up to 7,800 meters inside the Aggitis Cave in northeastern
Greece. There is a lot of work to be done on geographic distribution, population
dynamics, genetics, reproduction, nutrition, diseases, and farming of crayfish species in
Greece. Moreover, several actions should be undertaken to reform the existing legislation,
in order to protect the native species and their habitats.
Abstract: The populations of Pseudophoxinus epiroticus, endemic to Lake Pamvotis, Greece, collapsed between 1990 and 1998 and was about extinct in 2001. There are signs that it might now be in an early recovery stage.
Abstract: Wild brown trout were divided into two groups and kept in captivity for a period of
four months under a natural or artificial photoperiod regime. Fish of both groups (duplicates
with 81 females and 72 males in total) reached sexual maturation. The females held under
gradually increasing darkness conditions, exhibited sexual maturation earlier than the
controls. Males demonstrated a marginal acceleration in the timing of sexual maturation.
Hatching time, egg and fry survival and timing of fry emergence did not vary between the
experimental and control groups. Fecundity, milt volume and spermatocrit were unaffected
by artificial photoperiod. It is concluded that the photoperiodic regime did not compromise
gamete quality and viability of larvae or alevins, whereas the photoperiod modulated the
onset of maturity.
Abstract: In general, crayfish can be found in 19 out of 53 prefectures, forming isolated populations in relatively pristine water bodies. Three native species occur in Greek waters: Astacus astacus, Astacus leptodactylus and Austropotamobius torrentium as well as one alien species Pacifastacus leniusculus. Greece represents probably the most southern natural distribution limit for A. astacus and A. torrentium. Concerning non indigenous
crayfish species, P. leniusculus was imported from Sweden and Germany during the early and late 1980s, respectively, in order to replace A. astacus stocks which were diminishing at that time.
Abstract: Gibel carp Carassius gibelio exhibits gynogenetic reproduction by utilising the sperm of other species.
Over a period of twelve months, the spawning behaviour of gibel carp in Lake Pamvotis (NW Greece) was
monitored. Females almost exclusively (97.7%) composed the population, indicating gynogenesis using the sperm of other species. Reproduction began in March and lasted through April. Contrary to the situation reported in other ecosystems, common carp was not present in the spawning grounds during the spawning season of gibel carp; the most abundant other species present at that time was Rutilus ylikiensis. To evaluate the sperm donating results of R. ylikiensis as compared with other species of the lake, eggs of gibel carp were fertilised with sperm of R. ylikiensis (group 1), Carassius auratus (group 2), and Cyprinus carpio (group 3). Also, gibel carp eggs attached to natural substrates were collected from the spawning grounds (group 4). Hatching success ranged from 9-29% in group 4, compared to 95-98% in groups 1, 2 and 3. Over a period of 60 days after hatching, mortality ranged from 35% (group 1) to 56% (group 3), and specific growth rate from 2.4% (group 3) to 2.9% (group 1). We conclude that gibel carp can successfully utilise sperm of ylikiensis roach, which was the best available sperm donor option for the gynogenetically reproducing gibel carp of the lake.
Abstract: Once considered abundant, the Adriatic sturgeon (Αcipenser naccarii Bonaparte, 1836) is currently very rare in the Adriatic sea, with only a few individuals present in some surrounding rivers. There is some evidence that in the past, the species was found in the coastal waters of north-west Greece, around the island of Corfu and off the coast of Thesprotia, but now it appears to have virtually vanished from Greece’s coastal waters and river ecosystems. Dam construction, over-fishing and habitat destruction has completely eliminated the breeding population in the river Kalamas in Thesprotia. In November 2000, 1500 A. naccarii fry with a mean body weight of 1.2 g, from Lombardy, Italy, were released at selected sites on the river Kalamas. At the same time, 500 fish from the same stock were held indoors for intensive rearing. During the succeeding 13 months, experimental sampling indicated that the surviving fish had grown in size. There is evidence that the population is distributed in at least one region close to the site of release. The sturgeon reared indoors exhibited satisfactory growth, (specific growth rate SGR=1.7%• day-1) and had negligible mortality rates. From these results it seems that there is some prospect of successfully re-establishing A. naccarii in the river Kalamas. Re-stocking efforts can be improved by growing sturgeon fry under intensive rearing conditions to achieve larger size prior to release and to increase survival rates in the wild.
Abstract: Impact of copper (Cu2+) and lead (Pb2+) on the growth of microalgae Isochrysis galbana was studied. Algal
cultures were exposed to 0.01, 0.1, 1.0 mg/l Cu2+ and 0.01, 0.1, 1.0 mg/l Pb2+ for a period of 8 days. Biomass
growth was estimated by chlorophyll-a measurement. Cu2+ concentrations of 1.0 mg/l had significant effects on
Isochrysis galbana growth rate, while lower concentrations (0.01-0.1mg/l) caused a slow decline in algal growth. Comparable concentrations of lead (Pb2+) were found not to affect the algal growth.
Abstract: Early maturation is a major problem for the Atlantic salmon farming industry, associated with reduced growth performance, diversion of valuable feeds from growth to the reproductive process, mortalities, devaluation of the farming product and problems in farm logistics. Levels of ‘grilsing’ can be reduced, by providing additional artificial lighting on the cages. The additional light is thought to change the way the fish perceive ambient daylength, probably by alteration of diel patterns of circulating melatonin. However, little is known about the endocrine mechanism behind this.
One sea-winter Atlantic salmon were reared under additional light of different intensities, from late winter 1997 until June 1998, under commercial conditions. The light was provided by either submerged or above water light sources. Randomly distributed fish were blood sampled and the plasma was assayed for melatonin by radioimmunoassay.
Both light sources were effective in stimulating the overall growth rate; both also reduced the proportion of ‘grilsing’ by 50%. Mean night-time circulating melatonin levels were suppressed to a different extent depending on the light intensities, although no correlation between light intensity and melatonin levels was established. It is suggested that certain melatonin and light intensity threshold levels should be suppressed and exceeded respectively, in order to affect growth patterns and maturation.
Submerged light proved to be more efficient in transmitting high light levels within the water column, especially at the depths used by the salmon. Submerged lights proved to be much more economic in operation, ‘trouble-free’ during the day-to-day activities on the farm and environmentally friendly, with respect to light pollution levels.
The results suggest that additional light provided by submerged lights is a promising tool for both maturation control and enhancement of growth performance in Atlantic salmon farming.
