Recent changes in the trophic structure of the Black Sea

During the past few decades, the Black Sea has been subjected to various human impacts that have led to changes in the ecology of this inland sea. River runoff has introduced high levels of certain heavy metals and other toxic substances as well as detergents. Ship traffic has led to the introduction of new species, and fishing pressures have also altered the ecology of the area.
This paper reviews major ecological changes over the past 40 years. An increase in nutrients has caused eutrophication, with outbursts of phytoplankton blooms and changes in the species composition of these algae. Small-sized zooplankton species and gelatinous zooplankton have become more common, while many of the herbivorous copepods have decreased in abundance or have disappeared. The introduction of the predatory ctenophore Mnemiopsis leidyi in the 1980s has had significant impact on the plankton community and has led to a sharp decline in anchovy stocks. Decreased water transparency has led to a loss of macrophytic algae, except in shallow waters, and to a subsequent decline in the zoobenthos associated with this flora. Eutrophication has also led to decreased oxygen concentrations in the near-bottom water due to large amounts of decomposing phytoplankton, and regions of hypoxia and anoxia now appear on the shelf, with consequent reduction in benthic populations of invertebrates and demersal fish. The numbers of fish species harvested commercially have fallen from 26 to 5, but the total catch has increased, owing to increases in abundance of small fish (e.g., sprat) and horse mackerel, and to increased fishing effort.     

Major long‐term changes in the ecology of the Ythan estuary,Aberdeenshire, Scotland; how important are physical factors?

1. Long‐term data sets on macro‐algae, sediment invertebrates, shorebirds and physical parameters are explored for the Ythan estuary, Scotland. 2. Coverage by macro‐algal mats has increased over the last 40 years with significant impacts on the distribution and abundance of benthic invertebrates and their shorebird consumers. Areas of the estuary worst affected by the mats now support fewer Corophium volutator, whilst the abundance of this and other species has increased in areas less affected by mats, possibly through enrichment by non‐local macro‐algal detritus. 3. Shorebird abundance increased between the early 1960s and the 1980s, possibly in response to enhanced invertebrate abundance in unaffected areas, but has declined since, as algal mats continue to spread. 4. The cause of the increased biomass of macro‐algae is contentious, but the present analysis shows that the increase is unlikely to be related to changes in the physical characteristics of the estuary, which appear to have remained fairly constant over at least the last 30 years. Copyright © 1999 John Wiley & Sons, Ltd.     

Management of the introduction and transfer of marine molluscs

1. The introduction and transfer of marine molluscs for fisheries and aquaculture will include a risk of transporting competitors, predators, parasites, pests and diseases which can compromise intended molluscan culture and wild fisheries. 2. Introductions as well as transfers, in the course of normal trade, particularly of half-grown oysters, have been responsible for the establishment of several harmful and nuisance non-native species. Once established at a new locality these may continue to be moved by various means or by natural expansions of their range. 3. Several taxa have been associated with molluscan introductions and range expansions of these can be rapid should more than one dispersal vector be involved. 4. A Code of Practice for the introduction and transfer of marine organisms, prepared by the International Council for the Exploration of the Sea, provides a procedure which enables responsible movement of commercial species. In the case of an introduction it requires examination of the intended species by assessment of its likely ecological and genetic interaction with native species in advance of its release. It also includes measures, which if adopted, considerably reduce the risk of introducing accompanied unwanted species. 5. Introduced and useful species themselves, intended for culture, have seldom caused subsequent difficulties. 6. In this account the management of movements of non-native species, to and within northern Europe, are discussed. ©1996 by John Wiley & Sons, Ltd.     

Hypoxic wetland tributaries as faunal refugia from an introduced predator

Abstract– The introduction of Nile perch ( Lates niloticus ) into the Lake Victoria basin of East Africa has coincided with the decline or disappearance of hundreds of indigenous species. To mitigate additional biodiversity loss, we must learn what limits the spread of Nile perch and what habitats serve as refugia for prey species. Heavily vegetated wetlands may protect fishes from Nile perch predation by providing both structural and low-oxygen refugia for prey species tolerant of hypoxia. To examine the potential of wetlands as refugia we quantified the composition, persistence, and stability of fish assemblages in a wetland tributary of Lake Nabugabo, a satellite lake of Lake Victoria in which Nile perch have been introduced. Nile perch were extremely rare in the wetland, and nine of the 18 species that have disappeared from the open waters of the satellite lake were captured in the tributary in this study. Dissolved oxygen was chronically low in the river and may be important in shaping fish community characteristics. Faunal attenuation occurred as the dry season progressed and oxygen levels dropped; however, the most common species remained through seasonal changes. The chronically low oxygen conditions in the werland tributary may permit persistence of only hypoxia-tolerant species. However, wetland conditions seem to limit exploitation by Nile perch providing critical refugia for a subset of the basin fauna.     

Marine research,resources and conservation in the Azores

• 1 A history of marine research on the Azores is outlined. Until two decades ago most oceanic and littoral marine studies had been carried out by foreign scientists. Studies by Azorean scientists started to increase in the early 1980s when the University of the Azores was created.
• 2 Ocean circulation in this part of the Atlantic is described as a background for biogeography and diversity. The picture emerges that Azores is a ?meeting point’? for shallow water marine fauna and flora of different origins.
• 3 The species composition of one of the best studied groups of organisms, the fish, is compared between locations in the northeastern Atlantic. The work on fish is also compared with other well studied groups (algae and hydroids) to highlight the interest of the Azores as a natural biogeographical experiment.
• 4 Studies of marine resources began less than two decades ago. The development of demersal fisheries is described focusing on the switch from small-scale artisanal fishing to more commercial fisheries.
• 5 Conservation of species and legislation in force for molluscs, crustaceans, fishes, marine turtles, seabirds and marine mammals are summarized.
• 6 Protected marine areas already designated are defined, as well as new areas recommended.
• 7 The paper concludes with a discussion of current threats and future management strategies.

     

Discovering the dominance of the non-native European eel in the upper reaches of the Tone River system,Japan

To investigate the presence of non-native anguillid eels in Japanese waters, 141 eels were collected from seven sampling sites throughout the Tone River system. Genetic species identification showed an extraordinary dominance of the non-native European eel Anguilla anguilla in the uppermost site of the study area. Estimation of age from otoliths suggested that the European eels were introduced into the river in the 1990s, corresponding to previous reports from other Japanese water systems. Comparison of the von Bertalanffy growth curve parameters indicated that the European eels caught in the Tone River system appeared to have a similar or even higher growth rate than the same species in the original habitats in Europe. The long-term inhabitation and the normal development of European eels in Japanese waters suggest that regulations prohibiting the release of non-native eels and safeguards against accidental escape from culture ponds must be strictly maintained in order to ensure the conservation of the native Japanese eel.     

Biogeographical and ecological context for managing threats to coral and rocky reef communities in the Lord Howe Island Marine Park,south‐western Pacific

• 1. Quantitative subtidal surveys of fishes, macro‐invertebrates and sessile organisms at 33 sites within the Lord Howe Island Marine Park revealed a rich fauna and flora, including 164 fishes, 40 mobile invertebrate taxa, 53 coral and other sessile invertebrate taxa, 32 algal taxa, and two seagrasses. The biota in this newly‐zoned marine park was overwhelmingly tropical when species lists were tabulated; however, species with distributions centred on temperate coasts of eastern Australia and New Zealand occurred in disproportionately high densities compared with the tropical species.
• 2. Lord Howe Island reefs were generally in good condition. Virtually no bleached coral was observed (0.2% of the reef surface; 0.8% of total hard coral cover). Living scleractinian coral comprised the predominant group of organisms growing on reef surfaces, with 25.5% cover overall. Other major taxa observed were brown algae (18.8% cover) and red algae (16.9% cover).
• 3. Three distinctive community types were identified within the marine park—coral reefs, macroalgal beds and an offshore/open coast community. The distribution of these community types was strongly related to wave exposure, as indicated by an extremely high correlation with the first principal coordinates axis for biotic data (R²=0.80).
• 4. The close (<3 km) proximity of tropical coral and temperate macroalgal community types off Lord Howe Island is highly unusual, with localized patterns of nutrient enrichment suggested as the primary cause. The macroalgal community type is only known from a small area off the south‐western coast that is not protected from fishing. This community is considered highly susceptible to threats because of potential impacts of global warming and the possibility of expansion of sea urchin barrens. Coral bleaching and ocean acidification associated with global climate change also threaten the coral reef community, which includes relatively high numbers of endemic and near endemic fish species. Copyright © 2009 John Wiley & Sons, Ltd.

     

Invasion of stream fishes into low trophic positions

Abstract –  In the absence of other life-history constraints, fishes that can feed at low trophic levels (i.e., omnivores/detritivores) are predicted to be successful invaders because their food resources during the colonization and integration phases of the invasion are rarely limiting. Accordingly, we hypothesized that trophic position of non-native fishes in five mid-western and south-western U.S. river systems would be lower than native fishes. By standardizing δ ¹⁵N values with a common invertebrate (chironomids) across sites, we were able to evaluate differences in trophic position between natives and non-natives across sample locations and years. Our data tend to support this hypothesis, but there was notable spatial and temporal variation in this pattern. Moreover, three of four species generally fed at lower trophic positions in their introduced ranges than their native ranges. Although many factors influence the success of introduced species, our data suggest that the ability to forage on low-quality resources is a favourable trait for invasive fishes in lotic systems. Because these fishes feed at low trophic positions, it is important to consider how they will influence invaded systems, in contrast to invaders that feed at higher trophic positions. Future studies that evaluate the resistance of communities to invaders from different trophic positions would help understand the mechanisms that control the establishment and spread of species with different life-history traits.     

Occurrence and molecular characterization of betanodaviruses in fish and invertebrates of the Greek territorial waters

Betanodaviruses are small ssRNA viruses that cause viral encephalopathy and retinopathy, a severe neuropathological infectious disease in marine fish species worldwide. In the present study, the occurrence of betanodaviruses was investigated in wild and cultured populations of fishes and invertebrates of the Greek territorial waters. Betanodaviruses were detected in 35 species belonging to 21 families and 12 orders. To our knowledge, 23 of those are reported for the first time in Greek waters, while 11 of them are reported for the first time globally. The positive samples were subjected to sequencing and phylogenetic analysis of partial segments of RNA1 and RNA2 genes. Almost all the viruses circulating in Greece fell within RGNNV genotype, while reassortant viruses were detected in three samples, namely two inter‐RGNNV and one RGNNV/SJNNV. A novel unclassified Betanodavirus sequence was also identified. Most of the Greek sequence types have a restricted geographic distribution except for two RNA1 and one RNA2 sequence types that are widespread throughout the Mediterranean basin. The results of this study indicate the range of reservoirs/hosts of betanodaviruses and also their wide spread in the Greek territorial waters and reinforce the hypothesis that wild fish species transmit the virus to cultured ones and vice versa.     

Viral haemorrhagic septicaemia virus in marine fish and its implications for fish farming--a review

Viral haemorrhagic septicaemia virus (VHSV) has, in recent decades, been isolated from an increasing number of free-living marine fish species. So far, it has been isolated from at least 48 fish species from the northern hemisphere, including North America, Asia and Europe, and fifteen different species including herring, sprat, cod, Norway pout and flatfish from northern European waters. The high number of VHSV isolations from the Baltic Sea, Kattegat, Skagerrak, the North Sea and waters around Scotland indicate that the virus is endemic in these waters. The VHSV isolates originating from wild marine fish show no to low pathogenicity to rainbow trout and Atlantic salmon, although several are pathogenic for turbot. Marine VHSV isolates are so far serologically indistinguishable from freshwater isolates. Genotyping based on VHSV G- and N-genes reveals four groups indicating the geographical origin of the isolates, with one group representing traditional European freshwater isolates and isolates of north European marine origin, a second group of marine isolates from the Baltic Sea, a third group of isolates from the North Sea, and a group representing North American isolates. Examples of possible transfer of virus from free-living marine fish to farmed fish are discussed, as are measures to prevent introduction of VHSV from the marine environment to aquaculture.     

Distribution of benthic communities in the fjord‐like Bathurst Channel ecosystem,south‐western Tasmania,a globally anomalous estuarine protected area

• 1. Benthic assemblages in the fjord‐like Bathurst Channel estuarine system, south‐western Tasmania, vary over horizontal scales of 1–5 km and vertical scales of 1–10 m. Multivariate analysis indicated a total of eight major assemblages that characterize different sections and depths of the channel.
• 2. Because tannins in the low‐salinity surface water layer block light, foliose algae reach 5 m depth in the marine western region but do not penetrate below 1 m in the east. By contrast, sessile invertebrates are most abundant below 5 m depth in the west and below 2 m in the east. Deeper assemblages are unlikely to be continuous with assemblages in deeper waters off the Tasmanian coast as they are highly constrained by depth within particular sections of the estuary.
• 3. While the species composition of the Bathurst Channel biota is most similar to that found elsewhere in Tasmania, the structural character of the biota in terms of major taxonomic groups is more closely allied to that found in fjords of south‐western Chile and south‐western New Zealand. These three regions all possess wilderness settings, high rainfall that is channelled through estuaries as a low‐salinity surface layer, deep‐water emergence of fauna, rapid change in biotic communities over short horizontal and vertical distances, and high levels of local endemism. They also include some of the most threatened aquatic ecosystems on earth due to increasing human activity from a near pristine base, and the potentially catastrophic impacts of climate change. Copyright © 2009 John Wiley & Sons, Ltd.

     

Larval taxonomy and early identification of topmouth gudgeon Pseudorasbora parva: a screening tool to reduce risks of unintentional species translocation

Abstract  To minimise the risks of unintentional translocation and further spread of the non-native cyprinid, Pseudorasbora parva (Temminck & Schlegel) in the UK, various morphological and meristic characters of this species were measured, with a view to isolating the characters which allow reliable identification of this species during the early stages of development. The combination of myomere numbers, the nature of the internal pigmentation associated with the notochord and the lack of a single row of external melanophores along the route of the lateral line organ reliably facilitate the ability to distinguish this species from the native fauna of the British Isles. Thus, for the first time, fishery managers and environmental agencies have a much needed tool to screen for the presence young-of-the-year of this species when authorising movements of other fish species.     

Genetics of neotropical fish: from chromosomes to populations

The Neotropical freshwater fish fauna is very rich—according to the most recent catalogue 71 families and 4,475 species have been described. However, only a small amount of general information is available on the composition of Neotropical marine fishes. In Brazil, 1,298 marine species have been recorded. General analysis of available cytogenetic and population genetic data clearly indicates research has been mainly concentrated on freshwater fishes. Thus, today, cytogenetic information is available for 475 species of Characiformes, 318 species of Siluriformes, 48 species of Gymnotiformes, 199 freshwater species that do not belong to the superorder Ostariophysi, and only 109 species of marine fishes. For the species studied, only about 6% have sex chromosomes and about 5% have supernumerary or B chromosomes. A review of the cytogenetic studies shows that these data have provided valuable information about the relationships between fish groups, the occurrence of cryptic species and species complexes, the mechanism of sex determination and sex chromosome evolution, the distribution of nucleolus organizer regions, the existence supernumerary chromosomes, and the relationship between polyploidy and evolution. In relation to populations in Neotropical marine waters, the studies have shown the presence of cryptic species, which has important implications for fishery management. Different levels of genetic structuring can be found among Neotropical freshwater migratory fish species. This raises important implications for fish population genetic diversity and consequently its sustainable utilization in inland fisheries and aquaculture, specifically for conservation of ichthyo-diversity and survival.     

The trophic cascade from fish to benthic algae: manipulation of habitat heterogeneity and disturbance in experimental flow-through pools

To investigate the effects of environmental change on the trophic cascade from fish to benthic algae, two 26-day experiments were conducted in outdoor flow-through pools. Habitat heterogeneity was manipulated by filling grooves under tiles with wood. Disturbance was simulated by removing invertebrates and benthic algae from tiles with a stainless steel brush 10 days before the end of the experiment. Benthic invertebrates and algae rapidly colonized the pools. Japanese dace Tribolodon hakonensis that had been introduced as a top predator fed predominantly on ephemeropteran nymphs, chironomid larvae, trichopteran larvae, and benthic algae. Predation and intimidation by the dace reduced the number of ephemeropteran nymphs and lowered the percentage of invertebrates on the upper surfaces and sides of the tiles. Consequently, dace increased the algal biomass through a trophic cascade. When dace were present, a disturbance did not reduce the numbers of invertebrates at the end of the experiment, probably because most invertebrates recolonized the tiles and new invertebrates rapidly colonized the pools. The manipulation of habitat heterogeneity reduced the number of trichopteran larvae, but did not affect other invertebrates that used all surfaces of the tiles. Consequently, trophic cascades were not damped by these changes of habitat heterogeneity and disturbance.     

Rarity of marine benthic species in Great Britain: development and application of assessment criteria

1. One consideration in assessing the nature conservation importance of a site is the presence of ‘rare’ species. How pragmatic concepts of ‘rarity’ can be applied to the marine benthos in a national context for conservation and coastal zone management purposes are considered. 2. A means of assessing rarity, based on the total number of units of area where the species is known to occur within the 3-mile limit of British territorial waters, has been developed. Coastal marine species can therefore be assessed quantitatively using a consistent methodology comparable to terrestrial assessments in Britain. 3. Application of the criteria has required the collation and analysis of data on a national scale and involved wide consultation. Examples are given of species considered to be nationally rare or scarce (using the technique). The way the information has been disseminated is described. 4. The reasoning behind the work is discussed and some of the applications and limitations of the criteria and results are examined. Apparently this is the first time that rarity criteria have been developed for application in the marine benthos on a national scale. ©1996 by John Wiley & Sons, Ltd.     

Introductions of non-indigenous fish species for release and culture in The Netherlands

A total of 27 non-indigenous fish species has been introduced into the waters of The Netherlands, mainly during the 19th and 20th centuries: 12 European, 11 North American, 3 Asian and 1 South American species. Most of the introductions were made deliberately, some accidentally. Nearly all of the introduced fish are true freshwater species (23), the others are anadromous (4). The introductions were made with the aims of restocking declining populations of commercially important species, introducing new species as substitutes for the former, establishing new fisheries or for culture to produce fish for consumption, ornament and game. The extensive and prolonged attempts to restock inland waters with various salmonids have never met with success. The introduction of non-indigenous salmonids (e.g. chinook, lake whitefish) was also a failure. Even at the beginning of this century the inland waters of The Netherlands had become unsuitable for salmonids because of environmental deterioration although that was not understood at the time. The release of rainbow trout into natural waters is unsuccessful as they will not reproduce. Apart from the carp, the most successful introduction since mediaeval times has been the pikeperch (1901) which at present is the second most important freshwater species for fisheries. Four North American species, probably accidentally released, are fully acclimatized in our waters, and are even locally common. These are the eastern mudminnow, the black and the brown bullhead and the pumpkinseed.     

Invasions of rainbow trout and brown trout in Japan: A comparison of invasiveness and impact on native species

Many species of salmonids have been stocked into waters outside of their native range. The invasiveness and impact of these species on native species varies depending on their biological traits, and on environmental conditions, such as climate. In Japan, rainbow trout and brown trout, both listed in 100 of the world's worst invasive alien species by the International Union for Conservation of Nature, occur as non-native species. The invasiveness of these two species is thought to be related to seasonal flooding, given flood waters can physically damage fry and prevent population establishment. Rainbow trout have successfully invaded waters in Hokkaido, northern Japan, where the likelihood of flooding is low between June and July, when their fry emerge, but successful invasions are rare in regions south of Hokkaido. Brown trout, however, have successfully invaded waters not only in Hokkaido, but also other regions. Since brown trout have a similar life history to the native white-spotted charr and masu salmon, with fry emerging before the flood season, they are more suited to the Japanese climate than Rainbow trout. Rainbow and brown trout interact with native species in various ways, but a common outcome of these interactions is the displacement of native charr species. Legal regulations of non-native salmonids should be based on understandings of the ecological traits of each invasive species and regional impacts on native species. Given the ongoing nature of climate change, the nature and extent of the effects of rainbow and brown trout on native species might also change.     

Risk analysis of non-native three-spot cichlid,Amphilophus trimaculatus, in the River Cauvery (India)

The three-spot cichlid Amphilophus trimaculatus (Günther) is an ornamental fish known to be invasive but has not been assessed for India. The present study confirmed this non-native species’ identity using conventional and molecular methods, as well as its occurrence in the River Cauvery, the first for this species in a lotic environment outside its native range. Gut content analysis indicated a diet of predominantly insects. The river's water quality and habitat were conducive for the species’ growth and reproduction. Using the Aquatic Species Invasiveness Screening Kit, A. trimaculatus was ranked as posing a “high” risk of being invasive in the River Cauvery, with climate match analysis showing 58% similarity with the species’ native range. Vector and pathway analysis found that A. trimaculatus was introduced to India via the aquarium trade, although consignment origin remains unknown, and the most likely means of entry into the river and its tributaries was the species’ escaping from holding facilities. Subsequent dispersal and impact of the species on native fauna are discussed. The study's outcomes demonstrate the importance of using risk analysis protocols to inform management of non-native species in India, with suggestions provided for immediate and long-term measures for the species’ management.     

Prioritizing marine invasive alien species in the European Union through horizon scanning

1. The disproportionately low presence of marine species in the list of invasive alien species (IAS) of Union concern of the European Union (EU) Regulation 1143/2014 does not fully acknowledge the threat they pose to the EU marine environment.
2. In this study, the first EU‐scale Horizon Scanning (HS) focusing on marine alien species was performed, aiming to deliver a ranked list of species that should be of high priority for risk assessment (Article 5 of the EU IAS Regulation).
3. Species absent from or with a limited distribution in EU marine waters were targeted. In total, 363 alien species were initially screened for HS by a panel of experts, including a broad range of taxonomic groups. Species were scored for their likelihood of arrival, establishment, spread, and impact in EU waters.
4. A consensus workshop ranked 267 species, including a subset of 26 prioritized species. These species are considered to be mainly introduced by shipping (fouling and ballast water), via the Suez Canal, and aquaculture activities. The 26 priority species were also scrutinized in terms of feasibility of their management; 18 of them were suggested for performing risk assessments on the basis of the EU IAS Regulation.
5. Since biological invasions are dynamic and connected with accelerated globalization and diversified human activities, we recommend HS to be repeated periodically to review the species already listed and assess new ones.

     

Marine Biotoxins of Algal Origin and Seafood Safety

Abstract

Harmful algal blooms occur with the unchecked proliferation of algae in the marine environment, which oftentimes results in the production of hazardous marine biotoxins. Marine biotoxins are produced by several dinoflagellate and diatom species (e.g., Alexandrium, Gymnodinium, Gonyaulax, Pyrodinium, Protogonyaulax, Dinophysis, Prorocentrum spp., and Pseudonitzchia spp.). Significant human health effects have been reported after exposure to these toxins, including disease syndromes such as Paralytic Shellfish Poisoning (PSP), Neurotoxic Shellfish Poisoning (NSP), Ciguatera Fish Poisoning (CFP), Amnesic Shellfish Poisoning (ASP), and Diarrhetic Shellfish Poisoning (DSP). Of more recent interest has been the emergence of newly discovered toxic dinoflagellates caused in part by the increase in human and environmental interactions along coastal waters. Most notably, Pfiesteria piscicida and Pfiesteria-like organisms have been associated with numerous fish kills and have stimulated public concern over the potential threat these organisms may have on human health and seafood safety. This paper reviews the current literature on marine biotoxins of algal origin, with particular attention to public health issues associated with seafood safety.