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Un altro mare
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Un altro mare ricostruisce la storia della pesca e delle risorse alieutiche in Alto Adriatico e Laguna di Venezia negli ultimi due secoli. Un viaggio nel tempo che è stato possibile grazie alla raccolta ed analisi di documenti storici, archivistici, descrizioni naturalistiche, analisi statistiche e scientifiche, fonti orali, seguendo l’approccio dell’ecologia storica. Il quadro che emerge mostra il susseguirsi di innovazioni tecnologiche e fonti di disturbo ambientale che hanno prodotto profondi effetti sulle risorse sfruttate. Un mare diverso da quello che i pescatori di Chioggia erano soliti solcare a bordo dei loro bragozzi a vela. Un altro mare.
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... Some studies have used traditional (or local) ecological knowledge to reconstruct temporal population trends and discover near-extinctions of marine fauna [17], [20], [21], while studies that compare the results from scientific research with evidence based on fishers' experience have shown that both sources of knowledge give similar results and can be used to detect the essential trends [22]–[23]. In many cases, such as in our study of sensitive marine species in the Mediterranean, enlisting fishermen (as observers of the marine system) may be the only way to gather information for a scientific study or can be used to complement other sparse information sources (local archives, naturalists' diaries, old scientific explorations , etc.) [24], [25], [26]. Fishers, especially retired fishermen with professional careers often exceeding 40 years, can provide ecological knowledge on the functioning of marine systems and their resources [27]. ...
... Shark catches were 2 or 3 times more abundant in the 1940– 1959 study period than in the present, as declared by more than 60% of the fishers, and this proportion decreased significantly over time at the 5% significance level (Figure 4, bottom, andTable 4). are independent observers of the marine system, these results suggest that the abundance of large marine fauna has decreased considerably during the 20 th century in the Mediterranean Sea (in agreement with the results of other studies; e.g. [25], [26]), and therefore fishers' observations during a lifetime of professional activity can provide a qualitative measure of this decline. Fishing activities in the Mediterranean Sea have been exploiting marine coastal communities for centuries and the most vulnerable species disappeared long before the fishermen we interviewed started fishing. ...
... In other oceans, available long-term data series have revealed the impact of the fishing activity on elasmobranch populations, which is reflected in the reductions in species numbers and declining abundances [12], [35], [36]. In some cases, there is so little information on certain species [32] that trends cannot be assessed; however, it needs to be stressed that these same species, based on historical records, were once considered common [25]. It is therefore possible that although interviews with fishers or quantitative modelling cannot be used to evidence this, these species have effectively been eradicated. ...
We conducted interviews of a representative sample of 106 retired fishers in Italy, Spain and Greece, asking specific questions about the trends they perceived in dolphin and shark abundances between 1940 and 1999 (in three 20 year periods) compared to the present abundance. The large marine fauna studied were not target species of the commercial fleet segment interviewed (trawl fishery). The fishers were asked to rank the perceived abundance in each period into qualitative ordinal classes based on two indicators: frequency of sightings and frequency of catches (incidental or intentional) of each taxonomic group. The statistical analysis of the survey results showed that both incidental catches and the sighting frequency of dolphins have decreased significantly over the 60+ years of the study period (except for in Greece due to the recent population increase). This shows that fishers' perceptions are in agreement with the declining population trends detected by scientists. Shark catches were also perceived to have diminished since the early 1940s for all species. Other long-lived Mediterranean marine fauna (monk seals, whales) were at very low levels in the second half of the 20(th) century and no quantitative data could be obtained. Our study supports the results obtained in the Mediterranean and other seas that show the rapid disappearance (over a few decades) of marine fauna. We show that appropriately designed questionnaires help provide a picture of animal abundance in the past through the valuable perceptions of fishers. This information can be used to complement scientific sources or in some cases be taken as the only information source for establishing population trends in the abundance of sensitive species.
... From 1951, official national statistics of fishing fleet are available, however these data include only total fishing capacity (for details, see Barausse et al. 15,16 Despite the lack of reliable data on temporal changes in fishing effort, temporal changes in fishing techniques can contribute in interpreting landing statistics. The main temporal changes in fishing techniques of the Chioggia's fleet are represented by the introduction of mid-water trawls and beam trawls ('rapido') in the early 1960s, and hydraulic dredges in the early 1970s 20 . From the 1950s new technologies were progressively introduced, such as radar and ecosounder 20 . ...
... The main temporal changes in fishing techniques of the Chioggia's fleet are represented by the introduction of mid-water trawls and beam trawls ('rapido') in the early 1960s, and hydraulic dredges in the early 1970s 20 . From the 1950s new technologies were progressively introduced, such as radar and ecosounder 20 . Accordingly with the increase in fishing capacity, the improvement in technologies and the introduction of new techniques, the total landings increased from 1960s. ...
Long-term time series of species abundances can depict population declines and changes in communities in
response to anthropogenic activities, climate changes, alterations of trophic relationships. Here we present
a database of historical marine fishery landing data, covering a remarkably long time series (1945–2013) and
referring to one of the most exploited areas of the Mediterranean Sea, the Adriatic Sea. The database
includes two time series of landing data, 1945–2013 and 1997–2013, from the official statistics of the fish
market of Chioggia, where the major fishing fleet of the area operates. Comparisons between the landing
data of the database and landing data from other fisheries or data from scientific surveys support the
reliability of the time series in depicting changes in species abundances. The database is expected to be
used by fishery biologists and ecologists interested in depicting and understanding temporal variations in
species abundances and community composition, in relation to environmental and anthropogenic factors.
Integrating long-term ecological observations with experimental findings on species response and tolerance to environmental stress supports an understanding of climate effects on population dynamics. Here, we combine the two approaches, laboratory experiments and analysis of multi-decadal time-series, to understand the consequences of climate anomalies and ongoing change for the population dynamics of a eurythermal littoral species, Carcinus aestuarii. For the generation of cause and effect hypotheses we investigated the thermal response of crab embryos at four developmental stages. We first measured metabolic rate variations in embryos following acute warming (16-24 °C) and after incubation at 20 and 24 °C for limited periods. All experiments consistently revealed differential thermal responses depending on the developmental stage. Temperature-induced changes in metabolic activity of early embryonic stages of blastula and gastrula suggested the onset of abnormal development. In contrast, later developmental stages, characterized by tissue and organ differentiation, were marginally affected by temperature anomalies, indicating enhanced resilience to thermal stress. Then, we extended these findings to a larger, population scale, by analyzing a time-series of C. aestuarii landings in the Venice lagoon from 1945 to 2010 (ripe crabs were recorded separately) in relation to temperature. Landings and extreme climatic events showed marked long-term and short-term variations. We found negative relationships between landings and thermal stress indices on both timescales, with time lags consistent with an impact on crab early life stages. When quantitatively evaluating the influence of thermal stress on population dynamics, we found that it has a comparable effect to that of the biomass of spawners. This work provides strong evidence that physiological responses to climatic anomalies translate into population-level changes and that apparently tolerant species may be impacted before the ontogeny of eurythermy. These ontogenetic bottlenecks markedly shape population dynamics and require study to assess the effects of global change.
Although the Atlantic bluefin tuna has been studied for more than a century, the assessment of the East stock is characterised by a large amount of uncertainty. In 2000, this situation became so critical that quantitative stock assessment has been postponed. The first part of the present study aims to list the main difficulties that have led to the current situation and tries to discern between subjective and objective uncertainty. The former, which is due to an incomplete knowledge of the system and which has increased in the past few years, is mainly due to a decreasing quality of the catch and effort data, that has followed the establishment of a TAC. The latter source of uncertainty, which results from the underlying variability in stochastic processes, mainly relates, for this species, to spatial and temporal changes in stock size, growth and migration. The second part of this study presents the results of simulation modelling, which could be, in the meantime, an useful tool for short-term management of the East Atlantic and Mediterranean BFT stock.
Demersal fishing gear affects seabed habitats both directly and indirectly and modifies the
processes and dynamics of benthic communities. At present, scientific attention is focused on using the
functional approach to better understand the constraints that drive the recolonization of benthic fauna
subjected to fishing disturbance. The Northern Adriatic Sea has an extensive trawlable area that is
intensively exploited by a variety of trawling gear. Among these, the rapido, a beam trawl used to
catch flatfishes on mud substrate and pectinids on sand, appears to have the greatest impact on the
benthic habitat. We used various functional indicators (diversity indices, community structure, trophic
groups, production analysis, and exergy) to compare the medium-term (9-month) macroinfaunal
recolonization processes in sand and mud habitats treated with a single experimental rapido haul.
Recolonization was found to be a community-wide process. The early successional stages in the sand
habitat were dominated by scavenging organisms that peaked in abundance 7 d after the treatment. In
the mud habitat, the trend in scavenger activity was less distinct, although a peak in abundance was
recorded 1 month after the treatment. The functional analyses revealed that complete recovery required
at least 9 months in both habitats. Finally, data collected on the fishing ground near the sand experimental
area were analyzed in order to investigate the chronic disturbance caused by commercial trawling. The
fishing ground samples showed a higher spatial heterogeneity than the sand experimental samples.
Total abundance, total biomass, and production values in the fishing ground were comparable with the
lowest recorded values in the sand experimental area, and the exergy differences suggested that the
fishing ground’s benthic community remained in an early successional stage.
Thrips (fhysanoptera) are very small insects, widespread throughout the world with a preponderance of tropical species, many temperate ones, and even a few living in arctic regions. Of the approximately 5,000 species so far identified, only a few hundred are crop pests, causing serious damage or transmitting diseases to growing crops and harvestable produce in most countries. Their fringed wings confer a natural ability to disperse widely, blown by the wind. Their minute size and cryptic behavior make them difficult to detect either in the field or in fresh vegetation transported during international trade of vegetables, fruit and ornamental flowers. Many species have now spread from their original natural habitats and hosts to favorable new environments where they often reproduce rapidly to develop intense damaging infestations that are costly to control. Over the past decade there have been several spectacular examples of this. The western flower thrips has expanded its range from the North American continent to Europe, Australia and South Africa. Thrips palmi has spread from its presumed origin, the island of Sumatra, to the coast of Florida, and threatens to extend its distribution throughout North and South America. Pear thrips, a known orchard pest of Europe and the western United States and Canada has recently become a major defoliator of hardwood trees in Vermont and the neighboring states. Local outbreaks of other species are also becoming problems in field and glasshouse crops as the effectiveness of insecticides against them decline.
Sardine Sardina pilchardus (WALB.) is - together with anchovy Engraulis encrasicolus (L.) - one of the most important commercial fish species in the Mediterranean Sea and, in particular, in the Adriatic Sea. The mean value of the annual catch of sardine in the Adriatic Sea is around 50.000 t, in the period 1975-1996. Since 1975, the IRPEM is involved in research on sardine and anchovy abundance in the northern and central Adriatic Sea, by means of population dynamics methods. In this paper, the sardine stock biomass values estimated for the time interval 1975-1996 are discussed. These estimates were obtained using three methods based on different data inputs: Length Cohort Analysis (LCA), Virtual Population Analysis (VPA) and an ad hoc modified version of the DELURY model with recruitment index. A comparison between the biomass estimates derived from these methods was made. Values of biomass, as well as patterns over time, are consistent. In particular, strong fluctuations of biomass are evident. The possible effects of fishing effort on biomass were investigated and the stock-recruitment relationship analysed, in order to gain insight about the mechanisms underlying biomass fluctuations.
