Jellyfish as Prey: Frequency of Predation and Selective Foraging of Boops boops (Vertebrata,Actinopterygii) on the Mauve Stinger Pelagia noctiluca (Cnidaria,Scyphozoa)

In recent years, jellyfish blooms have attracted considerable scientific interest for their potential impacts on human activities and ecosystem functioning, with much attention paid to jellyfish as predators and to gelatinous biomass as a carbon sink. Other than qualitative data and observations, few studies have quantified direct predation of fish on jellyfish to clarify whether they may represent a seasonally abundant food source. Here we estimate predation frequency by the commercially valuable Mediterranean bogue, Boops boops on the mauve stinger jellyfish, Pelagia noctiluca, in the Strait of Messina (NE Sicily). A total of 1054 jellyfish were sampled throughout one year to quantify predation by B. boops from bite marks on partially eaten jellyfish and energy density of the jellyfish. Predation by B. boops in summer was almost twice that in winter, and they selectively fed according to medusa gender and body part. Calorimetric analysis and biochemical composition showed that female jellyfish gonads had significantly higher energy content than male gonads due to more lipids and that gonads had six-fold higher energy content than the somatic tissues due to higher lipid and protein concentrations. Energetically, jellyfish gonads represent a highly rewarding food source, largely available to B. boops throughout spring and summer. During the remainder of the year, when gonads were not very evident, fish predation switched towards less-selective foraging on the somatic gelatinous biomass. P. noctiluca, the most abundant jellyfish species in the Mediterranean Sea and a key planktonic predator, may represent not only a nuisance for human leisure activities and a source of mortality for fish eggs and larvae, but also an important resource for fish species of commercial value, such as B. boops.     

Deterministic Factors Overwhelm Stochastic Environmental Fluctuations as Drivers of Jellyfish Outbreaks

Jellyfish outbreaks are increasingly viewed as a deterministic response to escalating levels of environmental degradation and climate extremes. However, a comprehensive understanding of the influence of deterministic drivers and stochastic environmental variations favouring population renewal processes has remained elusive. This study quantifies the deterministic and stochastic components of environmental change that lead to outbreaks of the jellyfish Pelagia noctiluca in the Mediterranen Sea. Using data of jellyfish abundance collected at 241 sites along the Catalan coast from 2007 to 2010 we: (1) tested hypotheses about the influence of time-varying and spatial predictors of jellyfish outbreaks; (2) evaluated the relative importance of stochastic vs. deterministic forcing of outbreaks through the environmental bootstrap method; and (3) quantified return times of extreme events. Outbreaks were common in May and June and less likely in other summer months, which resulted in a negative relationship between outbreaks and SST. Cross- and along-shore advection by geostrophic flow were important concentrating forces of jellyfish, but most outbreaks occurred in the proximity of two canyons in the northern part of the study area. This result supported the recent hypothesis that canyons can funnel P. noctiluca blooms towards shore during upwelling. This can be a general, yet unappreciated mechanism leading to outbreaks of holoplanktonic jellyfish species. The environmental bootstrap indicated that stochastic environmental fluctuations have negligible effects on return times of outbreaks. Our analysis emphasized the importance of deterministic processes leading to jellyfish outbreaks compared to the stochastic component of environmental variation. A better understanding of how environmental drivers affect demographic and population processes in jellyfish species will increase the ability to anticipate jellyfish outbreaks in the future.     

Analysis of <Emphasis Type="Italic">Pelagia noctiluca</Emphasis> proteome Reveals a Red Fluorescent Protein,a Zinc Metalloproteinase and a Peroxiredoxin

Pelagia noctiluca is the most venomous jellyfish in the Mediterranean Sea where it forms dense blooms. Although there is several published research on this species, until now none of the works has been focused on a complete protein profile of the all body constituents of this organism. Here, we have performed a detailed proteomics characterization of the major protein components expressed by P. noctiluca. With that aim, we have considered the study of jellyfish proteins involved in defense, body constituents and metabolism, and furthered explore the significance and potential application of such bioactive molecules. P. noctiluca body proteins were separated by1D SDS–PAGE and 2DE followed by characterization by nanoLC-MS/MS and MALDI-TOF/TOF techniques. Altogether, both methods revealed 68 different proteins, including a Zinc Metalloproteinase, a Red Fluorescent Protein (RFP) and a Peroxiredoxin. These three proteins were identified for the first time in P. noctiluca. Zinc Metalloproteinase was previously reported in the venom of other jellyfish species. Besides the proteins described above, the other 65 proteins found in P. noctiluca body content were identified and associated with its clinical significance. Among all the proteins identified in this work we highlight: Zinc metalloproteinase, which has a ShK toxin domain and therefore should be implicated in the sting toxicity of P. noctiluca.; the RFP which are a very important family of proteins due to its possible application as molecular markers; and last but not least the discovery of a Peroxiredoxin in this organism makes it a new natural resource of antioxidant and anti-UV radiation agents.     

Gill damage to Atlantic salmon (Salmo salar) caused by the common jellyfish (Aurelia aurita) under experimental challenge

Background

Over recent decades jellyfish have caused fish kill events and recurrent gill problems in marine-farmed salmonids. Common jellyfish (Aurelia spp.) are among the most cosmopolitan jellyfish species in the oceans, with populations increasing in many coastal areas. The negative interaction between jellyfish and fish in aquaculture remains a poorly studied area of science. Thus, a recent fish mortality event in Ireland, involving Aurelia aurita, spurred an investigation into the effects of this jellyfish on marine-farmed salmon.

Methodology/Principal Findings

To address the in vivo impact of the common jellyfish (A. aurita) on salmonids, we exposed Atlantic salmon (Salmo salar) smolts to macerated A. aurita for 10 hrs under experimental challenge. Gill tissues of control and experimental treatment groups were scored with a system that rated the damage between 0 and 21 using a range of primary and secondary parameters. Our results revealed that A. aurita rapidly and extensively damaged the gills of S. salar, with the pathogenesis of the disorder progressing even after the jellyfish were removed. After only 2 hrs of exposure, significant multi-focal damage to gill tissues was apparent. The nature and extent of the damage increased up to 48 hrs from the start of the challenge. Although the gills remained extensively damaged at 3 wks from the start of the challenge trial, shortening of the gill lamellae and organisation of the cells indicated an attempt to repair the damage suffered.

Conclusions

Our findings clearly demonstrate that A. aurita can cause severe gill problems in marine-farmed fish. With aquaculture predicted to expand worldwide and evidence suggesting that jellyfish populations are increasing in some areas, this threat to aquaculture is of rising concern as significant losses due to jellyfish could be expected to increase in the future.     

Current status and future perspectives of Italian finfish aquaculture

Currently available data show that shellfish and finfish production in Italy, derived both from fisheries and aquaculture activities, is on the order of 474,000 tons, each activity representing 50 % of the total amount. In this context, the finfish aquaculture industry contributes on average 31 % to the national aquaculture production and on average 59 % of its value, giving a total amount of 72,000 tons and a value of around 351 million € (2010). According to FEAP statistics, Italy is the fourth largest finfish producer in EU27, after the UK, Greece, and Spain, while it is also one of the six largest finfish producers among the non-EU and EU member countries, together with Norway, UK, Greece, Turkey, and Spain. Presently, fish culture activities are mainly focused on rainbow trout (Oncorhynchus mykiss, 55.5 %), followed by European sea bass (Dicentrarchus labrax, 13.6 %), gilthead sea bream (Sparus aurata, 12.2 %), gray mullet (Mugil cephalus, 5.3 %), sturgeon (Acipenser spp., 2 %), and European eel (Anguilla anguilla, 1.7 %). Over the last 20 years, freshwater fish production and aquaculture (trout, carp, and eel) have decreased in Italy, with the exception of sturgeon. In contrast, marine fish production has significantly increased during the same period, and the two leading species, European sea bass and gilthead sea bream, presently contribute 25.8 % of the finfish production. From 1,900 tons in 1990, production reached 19,000 tons in 2010, with a 900 % increase, at an average percentage of 4.5 %. In addition, new marine fish species were successfully cultured over the same period. This review outlines the past and present situation of finfish culture in Italy and discusses future developments and priorities, with particular emphasis on new, emerging aquaculture species.     

A blooming jellyfish in the northeast Atlantic and Mediterranean

A long-term time series of plankton records collected by the continuous plankton recorder (CPR) Survey in the northeast Atlantic indicates an increased occurrence of Cnidaria since 2002. In the years 2007 and 2008, outbreaks of the warm-temperate scyphomedusa, Pelagia noctiluca, appeared in CPR samples between 45° N to 58° N and 1° W to 26° W. Knowing the biology of this species and its occurrence in the adjacent Mediterranean Sea, we suggest that P. noctiluca may be exploiting recent hydroclimatic changes in the northeast Atlantic to increase its extent and intensity of outbreaks. In pelagic ecosystems, Cnidaria can affect fish recruitment negatively. Since P. noctiluca is a highly venomous species, outbreaks can also be detrimental to aquaculture and make bathing waters unusable, thus having profound ecological and socio-economic consequences.     

水母旺发的诱因及对海洋环境的影响

水母旺发已成为一种新型海洋生态灾害,使海洋生态系统的结构和功能、海洋生态环境受到严重破坏.本文总结了水母旺发的可能诱因,重点探讨了水母旺发对海水生源要素、溶解氧、酸碱度以及生物群落的影响.结果表明: 水母旺发与其自身生理结构与生活史密切相关,其具有的身体结构简单、生长迅速、繁殖性强、世代间隔时间短及耐不良环境等特点,使其遇合适环境可迅速繁殖.水母旺发的主要直接诱因可能与海水温度变化有关,海水升温可导致水母食物增多,促进水母生殖,尤其对暖温性水母,更易引起水母聚集繁殖,形成旺发.富营养化、气候变化、过渡捕捞、生物入侵、栖息地改变也是水母旺发的重要影响因素.水母旺发可显著影响生源要素的形态和生物地球化学循环,水母排放NH₄⁺和PO₄^3-速率分别为59.1～91.5 μmol N·kg^-1·h^-1和1.1～1.8 μmol P·kg^-1·h^-1,可为浮游植物提供8%～10%和21.6%的N和P,释放溶解有机碳速率为1.0 μmol C·g^-1·d^-1.水母腐烂时总氮和总磷的释放速率可达4000 μmol N·kg^-1·d^-1和120 μmol P·kg^-1·d^-1,溶解有机碳的释放速率为30 μmol C·g^-1·d^-1;水母腐烂可影响水体的酸碱度与溶解氧含量,导致水体严重酸化与缺氧/无氧,pH降幅为1.3,平均耗氧量可达32.8 μmol·kg^-1·h^-1.水母旺发还可引起某些鱼类与浮游动物生物量的减少与重新分布,浮游微生物增加,间接导致浮游植物增加,引起海洋初级生产的异常.
     

Parasitic copepods of the common sole, Solea solea (L.), from the Eastern Mediterranean coast of Turkey

There is increasing interest in the common sole, Solea solea (Linnaeus), as an alternative fish species in aquaculture in the Mediterranean region, and parasitic copepods are a potential hazard for farmed finfish. This paper provides taxonomic information on two species of sea lice (family Caligidae) collected from S. solea in eastern Mediterranean waters off the Turkish coast. Caligus brevicaudatus A. Scott, 1901 and Caligus apodus (Brian, 1924) were both found and this is the first report of C. brevicaudatus in Turkish waters. The discovery of C. apodus on S. solea is a new host record. Key diagnostic characters of both species are reported, supported by light and scanning electron microscopy observations. During a 12-month survey a prevalence of 28% was recorded for C. brevicaudatus, whereas for C. apodus peak prevalence was much lower (3%).     

Coho Salmon (Oncorhynchus kisutch) Prefer and Are Less Aggressive in Darker Environments

Fish are capable of excellent vision and can be profoundly influenced by the visual properties of their environment. Ambient colours have been found to affect growth, survival, aggression and reproduction, but the effect of background darkness (i.e., the darkness vs. lightness of the background) on preference and aggression has not been evaluated systematically. One-hundred Coho salmon (Oncorhynchus kisutch), a species that is increasing in popularity in aquaculture, were randomly assigned to 10 tanks. Using a Latin-square design, every tank was bisected to allow fish in each tank to choose between all the following colour choices (8 choices in total): black vs. white, light grey, dark grey, and a mixed dark grey/black pattern, as well as industry-standard blue vs. white, light grey, dark grey, and black. Fish showed a strong preference for black backgrounds over all other options (p < 0.01). Across tests, preference strength increased with background darkness (p < 0.0001). Moreover, having darker backgrounds in the environment resulted in less aggressive behaviour throughout the tank (p < 0.0001). These results provide the first evidence that darker tanks are preferred by and decrease aggression in salmonids, which points to the welfare benefits of housing farmed salmon in enclosures containing dark backgrounds.     

Viral infections of aquatic animals with special reference to Asian aquaculture

Worldwide, the number of communicable diseases of animals raised in aquaculture continue to increase. Viral infections of cultivated shellfish, crustacea, and finfish have been frequently recognized in the past few years. In the Asian regions, penaeid shrimp and several teleost fish underwent epizootics associated with heavy losses in aquaculture. Baculoviruses are particularly harmful to shrimp and prawns. Herpes-, irido-, reo-, or rhabdovirus-like agents can cause outbreaks in fish farms. Viral diseases are important limiting factors in the expansion of aquaculture. However, studies on viral infections of aquatic animals have been focused primarily on economically important farmed fish. Therfore, certain viral diseases of teleost fish are relatively well understood. In contrast, our knowledge of viral infections of farmed aquatic invertebrates is still very spare. Although a great number of viruses have been detected in farmed molluscs and crustaceans, the pathogenicity and epizootiology of most of the agents is not known.     

Identification of jellyfish from Continuous Plankton Recorder samples

Previous analysis of the Continuous Plankton Recorder (CPR) long-term data set for the presence of ‘coelenterate’ tissue revealed changes in the frequency of jellyfish occurrence in the North Atlantic Ocean and North Sea; however, the identities of the jellyfish were unknown, causing uncertainty in interpreting these findings. To improve the utility of the ‘coelenterate’ data from the CPR, 62 CPR samples were selected for re-analysis from an area where the widespread occurrence of the holoplanktonic scyphomedusan, Pelagia noctiluca (Forsskål, 1775), was previously documented from net tows to test if the CPR sampled P. noctiluca. Examination of the samples revealed smears (<1 mm) of golden gelatinous tissue on the sampling mesh. Subsequent microscopic examination and measurement of nematocysts identified most of the smears as P. noctiluca. Indeed, P. noctiluca was identified on 53% of the CPR samples from the area that best coincided with the documented bloom area. Although hydrozoans were also identified in the samples, the characteristic golden colour of P. noctiluca and its distinct suite of nematocysts allowed identification to species level. The identification of other jellyfish may be more complicated due to the labour-intensive examination of samples and unclear delineation of nematocyst types when multiple similar species are present. Nevertheless, re-analysis of CPR samples holds great promise for identifying the underlying reason for increases in jellyfish occurrence in the CPR records.     

The status of farmed fish hearts: an alert to improve health and production in three Mediterranean species

The heart ventricles of farmed gilthead seabream (Sparus aurata), European seabass (Dicentrarchus labrax) and Senegalese sole (Solea senegalensis) have been examined and we compared them to the corresponding fish from wild populations. These results can help to understand the differences in farmed fish hearts and in the myocardial structure that this condition of growth can produce. Several parameters were measured in the two groups. Numerical comparisons included heart mass, cardiac and ventricular index, ventricle height:width ratio, width and alignment of bulbus arteriosus, ventricular angles and compacta thickness. We confirm that the normal shape of wild fish hearts can be modified as a result from the adaptation to different environments. These changes can modify the structure of myocardium and compromise the cardiac function in farmed species. The ventricle of farmed fish present differences in shape, were misaligned, rounder, with a wider bulbus and thinner compact layer. Further studies are necessary to reveal functional significance and possible causes of these abnormal hearts and improve the cardiac welfare of Mediterranean species in culture as a way of ensuring a level of production compatible with economic benefits.     

Morphological differences between wild and farmed Mediterranean fish

Gilthead seabream (Sparus aurata L.) and European seabass (Dicentrarchus labrax L.) are important commercial marine fish species both for aquaculture and fisheries in the Mediterranean. It is known that farmed individuals escape from farm facilities, but the extent of escape events is not easy to report and estimate because of the difficulty to distinguish between wild and farmed individuals. In this study, significant differences provided through morphometry evidence that the cranial and body regions of seabream and seabass are different regarding their farm or wild origin at different scales. Morphological variations have been shown to be a valuable tool for describing changes in shape features. Therefore, the biomass contribution of escapees to local habitats could be determined by identifying escaped individuals from fisheries landings as a first step to assess the potential negative effects of fish farm escapees on the environment, and their influence on wild stocks and local fisheries.     

Dynamics of a biofouling community in finfish aquaculture: a case study from the South Adriatic Sea

Biofouling is one of the challenges that can strongly affect the finfish farm economy. Although several studies on biofouling in aquaculture have been conducted in the Mediterranean Sea, they focused on specific taxa or were limited to a particular period of sampling. The present study investigated for the first time the development, composition and variation in a biofouling community in a finfish farm with immersion time, season and depth. The results indicate that all these factors influence biofouling succession and recruitment. Moreover, the species that had a crucial role in structuring the community and in the farm cleaning activities were the ascidian Styela plicata and the bivalve Mytilus galloprovincialis. Compared with the literature data, the results highlight the heterogeneity in the composition of the biofouling present in the Mediterranean Sea. Moreover, such knowledge of the biofouling community could provide important information about management efforts and the costs that farmers will face when siting new fish farms.     

How sea lice from salmon farms may cause wild salmonid declines in Europe and North America and be a threat to fishes elsewhere

Fishes farmed in sea pens may become infested by parasites from wild fishes and in turn become point sources for parasites. Sea lice, copepods of the family Caligidae, are the best-studied example of this risk. Sea lice are the most significant parasitic pathogen in salmon farming in Europe and the Americas, are estimated to cost the world industry €300 million a year and may also be pathogenic to wild fishes under natural conditions.Epizootics, characteristically dominated by juvenile (copepodite and chalimus) stages, have repeatedly occurred on juvenile wild salmonids in areas where farms have sea lice infestations, but have not been recorded elsewhere. This paper synthesizes the literature, including modelling studies, to provide an understanding of how one species, the salmon louse, Lepeophtheirus salmonis, can infest wild salmonids from farm sources. Three-dimensional hydrographic models predicted the distribution of the planktonic salmon lice larvae best when they accounted for wind-driven surface currents and larval behaviour. Caligus species can also cause problems on farms and transfer from farms to wild fishes, and this genus is cosmopolitan. Sea lice thus threaten finfish farming worldwide, but with the possible exception of L. salmonis, their host relationships and transmission adaptations are unknown. The increasing evidence that lice from farms can be a significant cause of mortality on nearby wild fish populations provides an additional challenge to controlling lice on the farms and also raises conservation, economic and political issues about how to balance aquaculture and fisheries resource management.     

A comparison of fatty acid,cholesterol and vitamin composition in sea bass [Dicentrarchus labrax (Linnaeus, 1758)] and sea bream [Sparus aurata (Linnaeus, 1758)] from three cage farm areas: Antalya and Muğla (Turkey) and İskele (Northern Cyprus)

In the present study the fatty acids, cholesterol and vitamin composition in farmed sea bass (8 fish per species per farm; weight range: 389.6–395.8 g, total length range: 297–316 mm) and sea bream (8 fish per species per farm; weight range: 386.8–391.7 g, total length range: 263–268 mm) from three cage farms (?skele in northern Cyprus, Antalya and Mu?la in Turkey) were compared during the harvesting period in June–July 2011. The results showed that the muscles of D. labrax and S. aurata farmed fish were rich in n‐3 fatty acids, but with important differences. For example, the muscles of sea bass farmed in ?skele were rich in docosahexaenoic acid (DHA) and n‐3 polyunsaturated fatty acids (PUFA). Palmitic acid (C16:0) was the primary saturated fatty acid, and oleic acid (C18:1 n‐9) the primary monounsaturated fatty acid in the muscle and liver samples of the cage‐farmed sea bass and sea bream. There were no significant differences in the cholesterol content in the muscles of sea bream farmed in ?skele, Antalya or Mu?la. In conclusion, the n‐3/n‐6 ratio in the muscle of farmed S. aurata and D. labrax is within the recommended limits for a healthy human diet, being very suitable for human nutrition.     

Modeling Parasite Dynamics on Farmed Salmon for Precautionary Conservation Management of Wild Salmon

Conservation management of wild fish may include fish health management in sympatric populations of domesticated fish in aquaculture. We developed a mathematical model for the population dynamics of parasitic sea lice (Lepeophtheirus salmonis) on domesticated populations of Atlantic salmon (Salmo salar) in the Broughton Archipelago region of British Columbia. The model was fit to a seven-year dataset of monthly sea louse counts on farms in the area to estimate population growth rates in relation to abiotic factors (temperature and salinity), local host density (measured as cohort surface area), and the use of a parasiticide, emamectin benzoate, on farms. We then used the model to evaluate management scenarios in relation to policy guidelines that seek to keep motile louse abundance below an average three per farmed salmon during the March–June juvenile wild Pacific salmon (Oncorhynchus spp.) migration. Abiotic factors mediated the duration of effectiveness of parasiticide treatments, and results suggest treatment of farmed salmon conducted in January or early February minimized average louse abundance per farmed salmon during the juvenile wild salmon migration. Adapting the management of parasites on farmed salmon according to migrations of wild salmon may therefore provide a precautionary approach to conserving wild salmon populations in salmon farming regions.     

Fish farms at sea: the ground truth from Google Earth

In the face of global overfishing of wild-caught seafood, ocean fish farming has augmented the supply of fresh fish to western markets and become one of the fastest growing global industries. Accurate reporting of quantities of wild-caught fish has been problematic and we questioned whether similar discrepancies in data exist in statistics for farmed fish production. In the Mediterranean Sea, ocean fish farming is prevalent and stationary cages can be seen off the coasts of 16 countries using satellite imagery available through Google Earth. Using this tool, we demonstrate here that a few trained scientists now have the capacity to ground truth farmed fish production data reported by the Mediterranean countries. With Google Earth, we could examine 91% of the Mediterranean coast and count 248 tuna cages (circular cages >40 m diameter) and 20,976 other fish cages within 10 km offshore, the majority of which were off Greece (49%) and Turkey (31%). Combining satellite imagery with assumptions about cage volume, fish density, harvest rates, and seasonal capacity, we make a conservative approximation of ocean-farmed finfish production for 16 Mediterranean countries. Our overall estimate of 225,736 t of farmed finfish (not including tuna) in the Mediterranean Sea in 2006 is only slightly more than the United Nations Food and Agriculture Organization reports. The results demonstrate the reliability of recent FAO farmed fish production statistics for the Mediterranean as well as the promise of Google Earth to collect and ground truth data.