Papers by Rosalia Ferreri
Studio dell'ecologia riproduttiva dell'acciuga europea (Engraulis encrasicolus) in relazione ai p... more Studio dell'ecologia riproduttiva dell'acciuga europea (Engraulis encrasicolus) in relazione ai principali parametri ambientali 6 A differenza dell'acquacoltura, la pesca costituisce una delle ultime attività dell'uomo che utilizza, a fini economici, le capacità produttive degli stock selvatici, senza manipolarne i cicli biologici naturali. Un'attività di pesca è quindi sostenibile soltanto se la cattura del pescato è commisurata alla capacità naturale degli stock di riprodursi ed accrescersi. Ogniqualvolta la pesca preleva più del "surplus di produzione" di uno stock e cioè il prelievo da pesca non è commisurato ai tassi di natalità, accrescimento e mortalità di una popolazione si ha sovrasfruttamento e l'abbondanza degli stock comincia a diminuire. Questa diminuzione può essere più o meno grave a seconda della struttura d'età e dello stato riproduttivo dello stock, nonché della variabilità nelle condizioni ambientali ed ecologiche. L'attività di pesca è, pertanto, un'attività economica che ha le fondamenta profondamente radicate nella biologia e nell'ecologia delle specie pescate e che, se vuole durare nel tempo, non deve considerare la cattura come una variabile indipendente dalla capacità di rinnovo degli stock (Rapporto Annuale sulla Pesca e sull'Acquacoltura in Sicilia, 2009). Oggi si assiste purtroppo ad una tragica diminuzione del pescato, molto spesso ricondotta a cause antropiche legate all'eccessivo sfruttamento delle coste e all'inevitabile inquinamento ambientale. Ecco perché la Comunità Europea ha promosso l'uso di misure selettive per proteggere, ad esempio, le classi giovanili degli stock ittici, dando impulso ad una maggiore sensibilizzazione verso il rispetto e la salvaguardia della ricca biodiversità marina mediterranea ormai così fortemente minacciata da una sempre crescente pressione antropica. Il Mediterraneo, essendo una mare quasi chiuso e a cui si affacciano numerosi paesi, è continuamente sottoposto ad uno sfruttamento intenso e a volte incontrollato, che ha reso necessaria la realizzazione di un piano di regolamentazione a livello europeo. La valutazione delle caratteristiche economiche dell'attività della pesca è strettamente collegata alla conoscenza dei relativi processi produttivi, connessi ai diversi sistemi e metodi di cattura delle specie ittiche, i quali sono strettamente dipendenti dalle caratteristiche biologiche dei pesci. Se si considerano i piccoli pelagici nello Stretto di Sicilia, fino ad anni recenti sono stati segnalati sintomi di crisi nel caso della sardina (Patti et al., 2004; Fiorentino et al., 2005; Patti Studio dell'ecologia riproduttiva dell'acciuga europea (Engraulis encrasicolus) in relazione ai principali parametri ambientali 7 et al., 2009a). Un'analoga tendenza alla diminuzione è stata riportata per le coste tirreniche siciliane (Rinelli et al., 2005). Se si considerano tuttavia le più recenti stime di biomassa condotte con le campagne idroacustiche, si è registrato, a partire dal 2006, un lieve miglioramento delle abbondanze di sardina mentre è scesa al minimo degli ultimi dieci anni l'abbondanza di acciuga (Patti et al., 2009a e b; fig. I.2). Sulla base delle recenti valutazioni presentate al Working Group on Small Pelagics (Patti et al., 2009a e b) si ritiene che lo stock di alici dal 2006 al 2008 sia caratterizzato da una biomassa pari a circa 5.500 t, che rappresenta il minimo storico dell'ultima decade. Fig. I.2. Stime idroacustiche di biomassa della popolazione di acciuga e sardina al largo della costa meridionale siciliana dal 1998 al 2008 (Patti et al., 2009). La flotta siciliana è la più importante e numerosa di Italia. In particolare, la flotta a strascico della Sicilia meridionale rappresenta una delle maggiori realtà produttive nel contesto della pesca italiana. La produzione siciliana rappresenta il 26% di quella nazionale; mentre i ricavi conseguiti dai battelli siciliani rappresentano il 31% del fatturato complessivo. Il settore della pesca marittima siciliana risulta, quindi, rilevante per il livello delle catture e, ancor più, per i ricavi conseguiti. Tra le numerose specie pescate, vanno segnalati in ordine le acciughe, i Studio dell'ecologia riproduttiva dell'acciuga europea (Engraulis encrasicolus) in relazione ai principali parametri ambientali 8 gamberi rosa e rossi, il pesce spada, i naselli, l'alalunga e il tonno rosso, le triglie di fango e di scoglio (Rapporto Annuale sulla Pesca e sull'Acquacoltura in Sicilia, 2009). La pesca delle acciughe rappresenta la principale risorsa di pesca, che costituisce quasi il 30% della produzione totale di pesce del Mediterraneo (Lleonart e Maynou, 2003); nonostante questa specie risulti sempre la più pescata dalla nostra flotta nazionale, non va sottovalutato il calo nelle catture (pari a 16000 t) registrato nel 2008 rispetto all'anno precedente. Sempre nel 2008, dal punto di vista economico, la specie che ha fornito il maggiore contributo alla formazione del fatturato complessivo è rappresentata dal pesce spada ma le acciughe risultano comunque la seconda specie in ordine di fatturato (IREPA, 2010; fig. I.3). Tab. I.3. Catture e ricavi (% sul totale sbarcato) delle specie ittiche più abbondanti, Sicilia 2008 (Fonte IREPA, 2010). Studio dell'ecologia riproduttiva dell'acciuga europea (Engraulis encrasicolus) in relazione ai principali parametri ambientali
Seasonal variation of reproductive traits of the caramote prawn in the Gulf of Tunis
Aquatic Living Resources, 2015
PloS one, 2014
A number of scientific papers in the last few years singled out the influence of environmental co... more A number of scientific papers in the last few years singled out the influence of environmental conditions on the spatial distribution of fish species, highlighting the need for the fisheries scientific community to investigate, besides biomass estimates, also the habitat selection of commercially important fish species. The Mediterranean Sea, although generally oligotrophic, is characterized by high habitat variability and represents an ideal study area to investigate the adaptive behavior of small pelagics under different environmental conditions. In this study the habitat selection of European anchovy Engraulis encrasicolus and European sardine Sardina pilchardus is analyzed in two areas of the Mediterranean Sea that largely differentiate in terms of environmental regimes: the Strait of Sicily and the North Aegean Sea. A number of environmental parameters were used to investigate factors influencing anchovy and sardine habitat selection. Acoustic surveys data, collected during the summer period 2002-2010, were used for this purpose. The quotient analysis was used to identify the association between high density values and environmental variables; it was applied to the entire dataset in each area in order to identify similarities or differences in the ''mean'' spatial behavioral pattern for each species. Principal component analysis was applied to selected environmental variables in order to identify those environmental regimes which drive each of the two ecosystems. The analysis revealed the effect of food availability along with bottom depth selection on the spatial distribution of both species. Furthermore PCA results highlighted that observed selectivity for shallower waters is mainly associated to specific environmental processes that locally increase productivity. The common trends in habitat selection of the two species, as observed in the two regions although they present marked differences in hydrodynamics, seem to be driven by the oligotrophic character of the study areas, highlighting the role of areas where the local environmental regimes meet 'the ocean triad hypothesis'.
Reproductive traits and seasonal variability of Merluccius merluccius from the Tunisian coast
Journal of the Marine Biological Association of the United Kingdom, 2014
ABSTRACT Merluccius merluccius is an economically and ecologically important demersal species inh... more ABSTRACT Merluccius merluccius is an economically and ecologically important demersal species inhabiting the Atlantic Ocean and the Mediterranean Sea; however, reproductive knowledge about this species, along the North African coast is still missing. Monthly samples were collected from November 2010 to October 2011 along the North Tunisian coast. Morphometric parameters were measured, and histological preparations of gonadic tissues provided detailed information on the reproductive biology. Ovary maturity data showed a protracted spawning season throughout the year, with peaks in January, April and August. In females of M. merluccius, seasonal variability in weight and length were noticed, with higher values in the first part of the study period (November-April) than from May to October. Analysing separately these two periods, significant relationships were observed between gonadic maturation indices and the somatic and gonadic indices, suggesting a seasonal differential use of energy intake. From November to May the fish alternate the use of their energy for body growth and reserves for later uses (i.e fat, muscle and liver mass) or for gonadic growth. From June to October the energy is converted mainly into gonad weight and less to somatic growth. The maturity ogives obtained by macroscopic and histological maturity staging methods showed significant differences; however, in both cases the length at first maturity estimates were around 29 cm. Nonetheless, when selecting the main spawning period, the L-50 estimation was heavily reduced to 24 cm, suggesting careful attention in the selection of the samples to be used specially for fishery management purposes.
Reproductive strategy and fecundity of meagre <i>Argyrosomus regius</i> Asso, 1801 (Pisces: Sciaenidae): implications for restocking programs
Scientia Marina, 2013
Variability of water mass properties in the Strait of Sicily in summer period of 1998–2013
Ocean Science Discussions, 2014
ABSTRACT The Strait of Sicily plays a crucial role in determining the water mass exchanges and re... more ABSTRACT The Strait of Sicily plays a crucial role in determining the water mass exchanges and related properties between western and eastern Mediterranean. The presence of sills to the east and west of the Strait of Sicily and the complex seabed topography modulate the thermohaline circulation of the Mediterranean basin. An anti-estuarine circulation is mainly characterized, from a dynamic point of view, by a two-layer system: a surface layer composed of Atlantic Water (AW) flowing eastward, essentially dominated by mesoscale processes, and a subsurface layer composed of Levantine Intermediate Water (LIW) flowing in the opposite direction; the topography appears to play an important role. Furthermore, there are transition water masses with variable hydrological characteristics. The dataset here studied is a time series 16 years long (1998-2013), which highlights the high horizontal and vertical interannual variability affecting the study area. Strong temperature-salinity correlations, in the intermediate layer, for specific time intervals, could be linked to the reversal of sub-surface circulation in the Central Ionian Sea. Moreover, a long-term monitoring of the hydrographic properties of water masses across this strait allow the modelers to assess the performance of hydrological models of this area.
Spatial variations in feeding habits and trophic levels of two small pelagic fish species in the central Mediterranean Sea
Marine Environmental Research, 2016
Fisheries Research, 2015
Information on the breeding behaviour of fish such as spatial segregation phenomena during spawni... more Information on the breeding behaviour of fish such as spatial segregation phenomena during spawning events is important both for understanding their reproductive ecology but also for correctly designing sampling schemes in stock assessment. The daily spawning pattern of the European anchovy, Engraulis encrasicolus, was assessed using a novel methodology that included the analysis of the hourly distribution of imminent and recent spawning stages using a combination of generalised additive models (GAMs) and of multinomial models for ordinal categorical data. To do so we used data from nine years of daily egg production method, DEPM, surveys, carried out in the Strait of Sicily. The spatial distribution and occurrence of actively spawning individuals were also analysed. Results showed that the actively spawning phase period (ASPP), i.e., the period from the onset of oocyte hydration to spawning ranged approximately 4.5 h between ca. 18:30 and 23:00 while a daily spawning peak was identified at 22:30. The sex ratio was skewed during the ASPP such that females exceeded males by ca. 20% at mid ASPP. During the ASPP the proportion of Day-0 females (i.e., females that spawned or would spawn the day of sampling) decreases with increasing bottom depth while outside the ASPP Day-0 spawners did not show any particular bathymetric pattern. In the study area, anchovies exhibit segregative spawning behaviour which drives spawners to select shallower waters, similar to other anchovy populations in the Mediterranean while in the Atlantic and in other clupeoid populations the opposite bathymetric trend has been observed.
Hydrobiologia, 2015
An analysis of the influence of environmental conditions on the pelagic fish community structure ... more An analysis of the influence of environmental conditions on the pelagic fish community structure and species distribution in two areas of the Central Mediterranean sea, the Sicilian-Maltese and the Libyan continental shelves, is presented. The Libyan waters suffer from the lack of historical information on these species, and a thorough characterisation of the pelagic fish community is missing for the entire study area. In summer 2008, two multidisciplinary surveys permitted for the first time the collection of acoustic, biological, and hydrological data in the Libyan, Maltese, and Italian waters of the Central Mediterranean.
Advances in Oceanography and Limnology, 2011
For the first time the structure of the anchovy stock was investigated in the Strait of Sicily: s... more For the first time the structure of the anchovy stock was investigated in the Strait of Sicily: sampling locations were in Sicily, in Tunisia and in the Adriatic Sea. A morphological approach to stock discrimination which involves morphometric landmarks analysis was adopted. The aim of this work is to describe any morphological variations between the samples areas and individuate possible different populations in order to obtain useful information for management of shared resources between Tunisian and Italian waters. Furthermore sexual dimorphism was investigated. Results of morphometric landmarks may suggest a high level of overlapping among Sicily and Tunisia. Instead, between the Sicilian and Adriatic population, it was observed a certain degree of isolation, suggesting the existence of two anchovy sub-populations connected by a possible migration of a small number of individuals. No differences between male and female individuals was observed. Results support the likely existence of an anchovy metapopulation with several sub-populations, one inhabiting the northern and southern parts of the Strait of Sicily. From a management perspective and under the 'precautionary approach', these sub-populations should be treated as shared stocks and conserved.
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Papers by Rosalia Ferreri