Ichthyofauna fisheries in Bahía de Navidad,Jalisco, Mexico,associated to the El Niño event 1997-1998

The ichthyofauna fished in Bahía de Navidad, Jalisco, Mexico in the Central Pacific was surveyed during 1998. Six thousand nine hundred and fourty-four organisms of 130 species were caught which weighted 3,231 kg. Nearly 30% of the species belonged to Carangidae. Haemulidae and Sciaenidae. The most important species in number and biomass were Microlepidotus brevipinnins, Caranx caninus and C. caballus. Species number, abundance and biomass fluctuated during the year. The largest number of species was caught in June (61), the minimum in March (33). January had the maximum abundance (1,397 organisms), while the minimum was obtained during August (251). The maximum biomass values were from January (556.5 kg), and the lowest from August (114.7 kg). Eighteen species accumulated 87% of the total abundance, while 20 species represented 86.3% of the biomass. There were large in differences species number, abundance and biomass nets of different mesh size.     

A quantitative comparison of recreational spearfishing and linefishing on the Great Barrier Reef: implications for management of multi-sector coral reef fisheries

This study compared the catch composition, catch per unit effort, and incidental impacts of spearfishers and linefishers engaged in a structured fishing program whereby fishing effort was standardized across time, space and skill level. It was found that (1) the catch composition of both groups of fishers overlapped considerably, (2) the numbers of target fish caught by spearfishers (156) and linefishers (168) were not significantly different, (3) the mean size of target fish caught by spearfishers (1.95 ± 0.1 kg, ±SE) was significantly larger than the mean size of target fish caught by linefishers (1.27 ± 0.06 kg), and (4) spearfishers retained 43% more biomass of target species than did linefishers (304 versus 213 kg, respectively). However, linefishers used ∼1 kg of bait for every 3 kg of target fish that were captured. Linefishers also caught far more undersized, undesirable, or protected fishes (i.e., bycatch) and caused far more pollution (i.e., lost gear) than did spearfishers. It is concluded that the overall impacts of recreational spearfishing and linefishing on fishery resources of the Great Barrier Reef are broadly equivalent (per unit of fishing effort), and that management regulations should be applied equitably across both fishing sectors. A management strategy of this type will simplify enforcement of fisheries regulations and avoid discrimination of particular fishers in local communities where both fishing methods are socially or culturally important.     

Vertical, lateral and diurnal drift patterns of fish larvae in a large lowland river, the Elbe

A ringnet was used to sample drifting fish quantitatively at distinct depth strata. This method was chosen to examine the lateral, vertical and diurnal drift patterns of fish fry during four sampling campaigns in May 1998 and 1999 in the middle Elbe River, close to the city of Schnackenburg (stream kilometre 475). It became apparent that the fish larvae concentrated mainly at the surface of the right side of the main channel. Fourteen fish species of the four taxonomic families Percidae, Cyprinidae, Osmeridae and Gadidae were caught. Percid fishes (pike‐perch and perch) dominated the caught fish fry assemblage. Several environmental parameters were included in a direct gradient analysis in order to detect influencing variables. The main significant qualities were a temporal aspect and the shore distance. Other important influencing variables were suspended particular matter (SPM), fishing depth, time of the day, current velocity and the filtered volume. Negative correlations of abundance and shore distances and concentrations of SPM were found for several species as well as for the total abundance.     

Fishery-Induced Changes in the Subtropical Pacific Pelagic Ecosystem Size Structure: Observations and Theory

We analyzed a 16-year (1996–2011) time series of catch and effort data for 23 species with mean weights ranging from 0.8 kg to 224 kg, recorded by observers in the Hawaii-based deep-set longline fishery. Over this time period, domestic fishing effort, as numbers of hooks set in the core Hawaii-based fishing ground, has increased fourfold. The standardized aggregated annual catch rate for 9 small (<15 kg) species increased about 25% while for 14 large species (>15 kg) it decreased about 50% over the 16-year period. A size-based ecosystem model for the subtropical Pacific captures this pattern well as a response to increased fishing effort. Further, the model projects a decline in the abundance of fishes larger than 15 kg results in an increase in abundance of animals from 0.1 to 15 kg but with minimal subsequent cascade to sizes smaller than 0.1 kg. These results suggest that size-based predation plays a key role in structuring the subtropical ecosystem. These changes in ecosystem size structure show up in the fishery in various ways. The non-commercial species lancetfish (mean weight 7 kg) has now surpassed the target species, bigeye tuna, as the species with the highest annual catch rate. Based on the increase in snake mackerel (mean weight 0.8 kg) and lancetfish catches, the discards in the fishery are estimated to have increased from 30 to 40% of the total catch.     

禁捕初期鄱阳湖鱼类群落的结构特征

为掌握禁捕初期鄱阳湖鱼类群落的结构特征, 研究于2020年4月(春季)、7月(夏季)、10月(秋季)和2021年1月(冬季)在鄱阳湖21个采样点开展了渔获物调查。全年共采集到57种鱼类, 隶属于8目12科43属。优势种有贝氏?(Hemiculter bleekeri)、短颌鲚(Coilia brachygnathus)、蛇(Saurogobio dabryi)、和似鳊(Pseudobrama simoni)等4种鱼类。江湖洄游型、江海洄游型和河流型鱼类物种数共占比45.61%, 平均体重<20 g的物种的丰度占所有渔获物丰度的88.47%。在空间结构上, 基于鱼类丰度的非度量多维排序分析将鄱阳湖分为通江水道和主湖区两个大的空间类群, 方差分析表明通江水道鱼类丰度显著低于主湖区, 但多样性高于主湖区。在季节变化方面, 不同季节渔获物丰度、生物量和多样性的差异极其显著, 高水位时期(夏、秋季)的多样性高于低水位时期(春、冬季)。2020年10月在鄱阳湖主湖区中部的S9和通江水道的S20两个采样点发现了鄱阳湖历史文献中没有记录的广盐性近海鱼类——鲻(Mugil cephalus), 可能得益于长江禁捕, 由于消除了捕捞压力, 促使了该鱼类的资源恢复和上溯, 也不排除其他人为因素的可能, 因而需要更长时间序列的跟踪和监测。研究为全面评估鄱阳湖禁捕的生态效果提供了基础数据, 也为制定鄱阳湖鱼类资源的保护政策提供了参考。     

Ecological indicators based on trophic spectrum as a tool to assess ecosystems fishing impacts

Trophic indicators were used to compare two Malian freshwater reservoirs whose main differences are based on their different fishing pressures. Data were collected from a scientific survey of small-scale fishery landings conducted in 2002/2003. The trophic levels of fish species caught by artisanal fisheries are estimated from observations of scientific fishing or from the metabase Fishbase. Important differences exist in the trophic structure of both reservoirs. In Selingue (with high fishing pressure), very few top predators are found in the catches while the low trophic level fishes increase in total catches. In Manantali (with low fishing pressure), the top predators contribute twice as much to catches compared to Selingue. Hence, the mean trophic level of catches in Selingue (2.80) is lower than in Manantali (2.97). When comparing these results with those of study made in 1994/1995, it clearly appears that the effects of the fishing pressure in Selingue are obvious through a decrease of 0.12 in the mean trophic level while in Manantali this mean level has increased by 0.33 due to a recent strategic targeting of top predators. Trophic spectra seem to be relevant tools to characterize exploited fish communities from multi-specific and multi-gear small-scale fisheries catch data.     

Factors affecting the number and mortality of seabirds attending trawlers and long-liners in the Kerguelen area

The factors affecting the number and the mortality rates of seabirds attending long-liners and trawlers fishing in the Kerguelen area were studied during four successive seasons (1994–1997), based on observations carried out onboard by dedicated observers. Twenty-four species of seabirds were observed attending fishing vessels, representing an average of 591 birds/census. The total numbers attending varied mainly according to the year, the cloud cover and the presence of offal from long-liners. The dumping of offal increased the numbers of birds attending the vessel, especially when the offal could be easily handled by birds. The activity of the vessels also affected the numbers attending, birds being more abundant during line setting and trawl hauling. White-chinned petrels were the most abundant ship-following seabirds, followed by black-browed albatrosses, giant petrels and cape petrels. The number of white-chinned petrels, black-browed and grey-headed albatrosses attending fishing vessels increased in the time between spring and autumn, whereas it was the reverse situation for giant petrels and cape petrels. Four species of seabirds were caught by fishing gear, mainly by long-lines: white-chinned petrels, and black-browed, grey-headed and wandering albatrosses. Taking into account the number of birds from each species attending long-liners and known to be potential by-catch, some species appear to be more susceptible to being caught than others. White-chinned and grey-headed albatrosses are caught in much higher proportions than the numbers present, whereas black-browed albatrosses are caught in lower numbers. Giant petrels are abundant around long-liners but were never caught. In long-liners, most birds were killed when the lines were set during the day or when the deployment of the scaring device was not successful, with an overall figure of 0.47 birds/1000 hooks. Only one albatross was caught when the lines were set during the night. White-chinned petrels represented 92.2% of all birds killed by long-liners. The number of birds caught varied significantly among months and among years. The type of bait used also affected the catch rate. The catch rate was related to the number of birds attending the long-liner only for black-browed albatrosses. Most birds killed by trawlers were entangled by the netsonde cable. The efficiency of mitigation measures in order to reduce seabird mortality is discussed and it is stressed that night setting is the most efficient way to reduce mortality and should be enforced everywhere when possible. However, further methods should be developed to reduce the mortality of species active at night, especially white-chinned petrels whose populations in the Indian Ocean may by threatened by long-line fisheries. Accepted: 15 October 1999     

Resilience of predators to fishing pressure on coral patch reefs

Numbers and biomass of piscivorous fish and their predation on other fish may often be high in undisturbed coral reef communities. The effects of such predation have sometimes been studied by removal of piscivores (either experimentally or by fishermen). Such perturbations have usually involved removal of large, highly vulnerable, mobile piscivores that are often actively sought in fisheries. The effects of fishing on smaller, demersal, semi-resident piscivores have been little studied. We studied such effects on the fish communities of patch reefs at Midway atoll by experimentally removing major resident, demersal, piscivorous fishes. First, four control reefs and four experimental reefs were selected, their dimensions and habitats mapped, and their visible fish communities censused repeatedly over 1 year. Census of all control and experimental reefs was continued for the following 39 months, during which known piscivores were collected repeatedly by hand spearing. Records were kept of catch and effort to calculate CPUE as an index of predator density. Spearfishing on the experimental reefs removed 2504 piscivorous fish from 12 families and 43 taxa (mostly species). The species richness of the catch did not show an overall change over the duration of the experiment. Spearman rank correlation analysis showed some unexpected positive correlations for density in numbers and biomass of major fished piscivorous groups (especially lizardfish) over the experiment. Only two relatively minor fished piscivorous taxa declined in abundance over the experiment, while the overall abundance of piscivores increased. Visual censuses of fish on the experimental reefs also failed to show reduction of total piscivores over the full experimental period. No significant trend in the abundance of lizardfish censused over the full period was apparent on any of the control reefs. The high resilience of piscivores on these experimental reefs to relatively intense fishing pressure could result from their protracted recruitment seasons, high immigration rates, cryptic habits, or naturally high abundances. A major factor was the high immigration rates of lizardfish, replacing lizardfish and other less mobile piscivores removed from the reefs by spearing. On the fished reefs, the removed lizardfish population replaced itself >20 times during the experiment; other piscivorous taxa replaced themselves only 5 times.     

The influence of diel cycle,tidal direction and trawl alignment on beam trawl catches in an equatorial estuary

Synopsis Using a 3 m beam trawl, catch variation in the fish and prawn assemblage of the Labu estuary, Papua New Guinea was investigated during July and December 1981 and September 1984. About six times more organisms, three and a half times the biomass and twice as many species were caught per trawl at night than during the day. The greatest number of species, individuals and biomass were caught just after dusk. With the exception ofSecutor ruconius, there was no significant difference in the catches trawled at ebbing and flooding tides. Over twice as many individuals ofS. ruconius were caught during ebbing tides. Alignment of trawl direction in relation to the tidal current did not have a significant effect on the fish catch, but affected the prawn (Metapenaeus demani) catch. It is postulated that most species are not carried to and fro by tidal currents, but maintain their position in the estuary with respect to the substratum. Only prawns appeared to be carried by the currents. This study indicates that the most representative trawl results in terms of species diversity and abundance in shallow estuaries may be obtained at night and, that in estuaries with a small tidal range, tidal direction and velocity have little influence on catch. It also indicates that analyses of demersal nekton assemblages from daytime only estuarine trawl surveys must be approached with caution.Lizard Island Research Station     

浅水湖泊鱼类群落结构评估: 复合网目刺网与网簖的比较

准确评估鱼类群落结构是渔业管理和鱼类资源养护的必要前提, 而不同渔具采样结果往往会产生较大差异。研究同时采用欧洲标准采样网具-复合网目刺网(Multi-mesh gillnet)和中国传统网具-网簖对长江中游典型浅水湖泊扁担塘的鱼类群落结构进行了评估。2种网具共采集到27种鱼类, 并发现黄尾鲴(Xenocypris daviai)和湖鲚(Coilia nasus taihuensis)2种新记录种, 扁担塘的鱼类群落结构较1999年和2003年均发生了较明显的改变。2种渔具捕获的鱼类组成、相对丰度和生物量以及鱼类体长分布频率均存在显著性差异。基于鱼类的相对生物量和相对丰度的NMDS排序表明2种网具捕获到的鱼类群落结构也存在显著差异。另外还比较了复合网目刺网与其他定量采样网具间的差异, 作者认为复合网目刺网比较适合长江中下游浅水湖泊鱼类群落研究的定量取样, 但仅凭单一网具评估鱼类群落结构具有局限性。     

Effects of trawling on the diets of common demersal fish by‐catch of a tropical prawn trawl fishery

The ecological effect of prawn trawling on the benthos of the Gulf of Carpentaria, northern Australia, was investigated by examining stomach contents of common demersal fishes incidentally caught as by‐catch in the fishery. Fishes were collected from high and low fishing intensity sites in three regions based on vessel monitoring system data. The diets of eight species of benthic fish predators were compared between regions and fishing intensities. A regional effect on diet was evident for seven species. Only one generalist species had no significant difference in diet among the three regions. For the comparisons within each region, five predator species had significantly different diet between high and low fishing intensities in at least one region. Across the three regions, high fishing intensity sites had predators that consumed a greater biomass of crustaceans, molluscs and echinoderms. At low fishing intensity sites, predators had diets comprising a greater biomass of cnidarians and teleosts, and a different assemblage of molluscs, crustaceans and fishes. These changes in diet suggest that there may have been a shift in the structure of the benthic community following intensive fishing. Analysis of predator diets is a useful tool to help identify changes in the benthic community composition after exposure to fishing. This study also provided valuable diet information on a range of abundant generalist benthic predators to improve the ecosystem modelling tools needed to support ecosystem‐based fisheries management.     

Natural fishing experiments in marine reserves 1983–1993: community and trophic responses

 This study examined the effect of fishing on the density, biomass, species richness and overall structure of the reef fish community at two islands (Sumilon and Apo) in the Philippines from 1983 to 1993. A series of natural fishing experiments over this period involving marine reserves were monitored at each island, where estimates of fishing intensity and selectivity were available. Fishing intensity (15% and 25% of biomass removed per year at Sumilon and Apo, respectively) was high enough to affect total community biomass, but not density, significantly. Species richness was not affected significantly by fishing, except at Sumilon reserve. The fishery was relatively non-selective with most families/trophic groups caught roughly in proportion to their contribution to community biomass. Thus fishing did not alter the relative abundance of the major families/trophic groups significantly, except during a period of use of explosives and drive nets in the Sumilon reserve. At the level of family/trophic group the community displayed strong resilience of structure. There was little evidence of secondary effects e.g. declines in abundance of large predators resulting in measurable increases in abundance of their prey. This resilience of the community to the effects of fishing most likely results from three important community attributes (open nature of the component populations, likely maintenance of upstream recruitment supply and apparent lack of any obvious “keystone” species or families) and one important characteristic of the fishery (relatively non-selective with respect to the components of the community). Accepted: 30 June 1998     

Gear type,species composition and economic value of fisheries in the mangroves of Pak Phanang,Thailand

Fishing gear and methods, catch composition, annual catch numbers and the monetary value of fisheries based in the mangroves of Pak Phanang, Nakhon Si Thamarat province, Thailand, were studied from September 2004 to February 2005. The fishing gear and methods were surveyed by visual observation and interviews. Sample catches were taken for each type of fishing gear and method. Semi-closed questionnaire surveys were conducted among fishers, local traders, local administrative officers and related organizations to derive information on utilized species, gear and methods, fisher and fishery status, and trading and catch price. The Pak Phanang mangrove fishery has three types of multi-species capture gear: channel traps, gill nets and lift nets. It also has three kinds of single-species (group) gear/methods: crab traps, catfish hooks and hand capture using a long tail fishing boat. A total of 57 fish species in 27 families, and 23 shell fish species in 8 families were recorded from the catch samples. Penaeid shrimp (25%), and ambassid (31%) and mugilid (24%) fishes were the abundant groups in the channel traps, while ariid (36%) and mugilid (19%) fishes were abundant in the lift net catches. Ambassid (42%) fish dominated the gill net catches. Species richness (number of species) varied depending on sampling month and type of fishing gear. The total annual catch and its monetary value were estimated to be 442–551 tons and US $368,038–733,973, respectively. The estimated annual catch per unit area of mangrove was 63–79 kg ha⁻¹, which generated a market value of US $368,038–733,973, respectively. The estimated annual catch per unit area of mangrove was 63–79 kg ha⁻¹, which generated a market value of US 52–105.     

永兴岛附近海域珊瑚礁鱼类群落结构特征

为更好地保护和管理西沙永兴岛附近海域珊瑚礁鱼类,于2020—2021年对永兴岛上岸渔获物进行了调查研究,分析了鱼类群落结构组成及其变化和演替特征。结果表明:调查共发现永兴岛附近海域珊瑚礁鱼类101种,隶属于5目21科,以鲈形目鱼类最多,占总种类的84.16%,生物量超总渔获物的90%;科级水平鹦嘴鱼科鱼类最多,达21种,生物量超总渔获物的45%。28种珊瑚礁鱼类是永兴岛附近海域主要捕捞对象,占总渔获物的80%以上。永兴岛附近海域珊瑚礁鱼类呈现过度捕捞,一是主要渔获物中的中大型鱼类均重偏小;二是本海域个体体型最大的鱼类出现较多消亡;三是肉食性鱼类大量消亡;四是植食性鱼类生物量占比超过了肉食性鱼类。永兴岛附近海域珊瑚礁鱼类已经演替到以植食性鱼类为主导的生态系统;大量海胆的出现,表明了这一珊瑚礁生态系统在进一步衰退,向以海胆为主导的生态系统演变。保护西沙永兴岛附近海域珊瑚礁鱼类已经刻不容缓,需要严格地控制本海域的捕捞强度。     

Dynamics of artisanal fisheries in two Brazilian Amazonian reserves: implications to co-management

In this study we compare the dynamics of artisanal fishery in two adjacent reserves located in the Brazilian Amazon, Mamirauá (being managed for more than 12 years) and Amanã (initiating a management process), through the record of 485 fish landings in one fishing community in each reserve during high and low water seasons in 2003. Our goals were, first, to make a rapid and comparative assessment of some main aspects of fisheries in these two communities (fish species caught, CPUE, fishing gear and habitats exploited). Second, we used such data to evaluate if management strategies already in place in Mamirauá would be also valid for Amanã. Third, we compared fishing CPUE between the two communities, in order to check if co-management measures have contributed, at least partially, to preclude over-fishing, maintaining a higher fishing reward in Mamirauá reserve. We analyzed fisheries directed to the two most important marketable fishes in the region: the pirarucu (Arapaimas gigas) and the tambaqui (Colossoma macropomum), besides those fisheries aimed to subsistence and lower valued fishes. Our results indicated that the tambaqui was intensively fished year-round in Mamirauá, while Amanã fishers caught a higher variety of fishes, including catfishes and migratory scale fishes. Such differences might reflect differences in gear used and habitat exploited by fishers during the high water season. Mamirauá fishers caught a higher fish biomass considering both marketable and all fishes. Differences in gear used, habitats exploited and fishes caught during high water season indicate that distinct management initiatives might apply for each reserve. Notwithstanding their differences, both communities exploited the commercial fishes (tambaqui and pirarucu) in a similar way during the low water season. Therefore, the higher mean fishing yield (CPUE) observed in Mamirauá may be partially attributable to co-management measures, considering that Mamirauá has possibly been experiencing a higher fishing intensity than Amanã. Fishing related data are seldom available in Brazil and other tropical developing countries. We thus provided a framework of fast assessment of fishing dynamics, which may represent a first and useful step for management initiatives in the absence of more detailed data.     

Impacts of the live reef fish trade on populations of coral reef fish off northern Borneo

The live reef fish trade (LRFT) is one of the greatest but least-quantified sources of fishing pressure for several species of large coral reef fish across the Indo-Pacific. For the first time we quantify the localized impact of the LRFT. We collected data from three LRFT traders in northern Borneo, which yielded information on daily fishing effort and the species and mass of all fishes sold every day by individual fishers or vessels over 2, 3 and 8 years. Total monthly catch and relative abundance (catch-per-unit-effort) declined significantly in several species, including the most valuable species the Napoleon wrasse (Cheilinus undulatus, estimated changes of -98 and -78% over 8 years in catch and relative abundance, respectively) and lower-value bluelined groupers (Plectropomus oligocanthus: -99 and -81%) and Epinephelus groupers (-89 and -32%). These severe declines were rapid, species-specific and occurred in the first 2-4 years of the dataset and are, we believe, directly attributable to the LRFT. This has crucial implications for future data collection and monitoring if population collapses in other parts of the LRFT and similar wildlife trades are to be successfully detected.     

Global assessment of the status of coral reef herbivorous fishes: evidence for fishing effects

On coral reefs, herbivorous fishes consume benthic primary producers and regulate competition between fleshy algae and reef-building corals. Many of these species are also important fishery targets, yet little is known about their global status. Using a large-scale synthesis of peer-reviewed and unpublished data, we examine variability in abundance and biomass of herbivorous reef fishes and explore evidence for fishing impacts globally and within regions. We show that biomass is more than twice as high in locations not accessible to fisheries relative to fisheries-accessible locations. Although there are large biogeographic differences in total biomass, the effects of fishing are consistent in nearly all regions. We also show that exposure to fishing alters the structure of the herbivore community by disproportionately reducing biomass of large-bodied functional groups (scraper/excavators, browsers, grazer/detritivores), while increasing biomass and abundance of territorial algal-farming damselfishes (Pomacentridae). The browser functional group that consumes macroalgae and can help to prevent coral–macroalgal phase shifts appears to be most susceptible to fishing. This fishing down the herbivore guild probably alters the effectiveness of these fishes in regulating algal abundance on reefs. Finally, data from remote and unfished locations provide important baselines for setting management and conservation targets for this important group of fishes.     

Diel,semi‐lunar and seasonal patterns in the fish community of an intertidal zone of the Yangtze estuary

The structure and temporal variations of the fish community in the intertidal estuarine zone of shallow mud areas have been poorly studied in China. This paper analyses the diel, semi‐lunar and seasonal patterns of fish assemblages in the Yangtze estuary in 2006. Fish were collected by consecutive day and night samplings using tide‐stow‐nets deployed parallel to each other in three stations. A total of 56 fish species belonging to 21 families was caught during the study period. The family Cyprinidae dominated with 25 species. Freshwater fish species were the important dominant commercial fishery species and well represented with five species (sharpbelly Hemiculter bleekeri, goldfish Carassius auratus, bream Parabramis pekinensis, likely‐bream Pseudobrama simony, and glossy yellow catfish Pelteobagrus nitidus) in the three stations. Juvenile fishes dominated the fish community, comprising 93.9% in station 1 and 96.6% in station 2 of the total abundance. The number of fish species in day tides was slightly lower than those in night tides in spring and summer, but the opposite in other seasons. In neap tides, the numbers and abundance of fish species were both lower than those in the spring tides. Fish abundance was lowest in winter, increasing during spring and summer (March–September) in both stations 1 and 2, with obviously large fluctuations in each season. The pattern of habitat selection of fishes could effectively decrease the food competition of intraspecies or interspecies and favour the growth and nursing of young fishes. These findings indicate that the intertidal zones in the estuary may serve as important nursery areas for fish communities.     

Coastal Fisheries in the Eastern Baltic Sea (Gulf of Finland) and Its Basin from the 15 to the Early 20th Centuries

The paper describes and analyzes original data, extracted from historical documents and scientific surveys, related to Russian fisheries in the southeastern part of the Gulf of Finland and its inflowing rivers during the 15- early 20^th centuries. The data allow tracing key trends in fisheries development and in the abundance of major commercial species. In particular, results showed that, over time, the main fishing areas moved from the middle part of rivers downstream towards and onto the coastal sea. Changes in fishing patterns were closely interrelated with changes in the abundance of exploited fish. Anadromous species, such as Atlantic sturgeon, Atlantic salmon, brown trout, whitefish, vimba bream, smelt, lamprey, and catadromous eel were the most important commercial fish in the area because they were abundant, had high commercial value and were easily available for fishing in rivers. Due to intensive exploitation and other human-induced factors, populations of most of these species had declined notably by the early 20^th century and have now lost commercial significance. The last sturgeon was caught in 1996, and today only smelt and lamprey support small commercial fisheries. According to historical sources, catches of freshwater species such as roach, ide, pike, perch, ruffe and burbot regularly occurred, in some areas exceeding half of the total catch, but they were not as important as migrating fish and no clear trends in abundance are apparent. Of documented marine catch, Baltic herring appeared in the 16^th century, but did not become commercially significant until the 19^th century. From then until now herring have been the dominant catch.     

History,ecology and trends for artificial reefs of the Ligurian sea,Italy

From 1970 to the present 10 artificial reef sites have been developed in coastal waters of the Ligurian Sea, Italy. They range from Ventimiglia, in the west, to La Spezia, in the east, with the largest and best known reef complex being located in the Gulf of Genoa at Loano and consisting of 2,745 m³, about 5,200 t of material and covering a surface of 350 ha. Design and construction practices have advanced from an initial, unsuccessful effort that used automobile bodies (now banned) to current use of custom-designed concrete modules deployed systematically. Funding for reef construction has come since 1983. The earliest aim of reefs was as a physical barrier to protect habitats against illegal otter trawl fishing. Newer objectives include habitat restoration, enhancement of biodiversity and fishing catch, and research to test materials and designs for physical and ecological performance. Reefs also functions as environmental observation stations, with the invasive species Caulerpa taxifolia (Vahl) C. Agardh, being recorded on the reef at Alassio. For some Artificial Reefs (Ars), benthic organisms and fishes, settlement, biomass and development of community are recorded. In Loano AR, immersed in 1986, more than 150 algae species are recorded, more than 200 benthic animal species and 78 species (87 taxa) of fishes. Fifty-six species (61 taxa) of fishes are recorded by visual census, the others are caught only by trammel net and long line. Trammel catches at Loano are on average about 2.32 kg/100 m net. Comparisons among ARs reveal that age of the reef, location and presence of seagrass meadows are crucial for success. An indication of functional equivalence between ARs and natural rocky reefs is seen if both fish and sessile macrobenthos are compared. After 34 years of investigation a database comprising at least one hundred scientific articles based on research programs of up to 15 years, and other unpublished reports, provides information to guide future planning of reefs. On the basis of acquired experience, some management advice is suggested and the best design for the basic module in the Ligurian sea is described. The role of ARs, providing protection of coastal environment against the illegal otter trawling, nursery, microhabitat and food supply, while increasing biodiversity, biomass of benthos and fishes, and facilities for ecotourism, is outlined.