108 research outputs found
Catchability and survival of the resources during fishing operation
The present Ph.D. thesis aims to test and evaluate by-catch reduction devices (BRDs) that minimize the retention of undersized fish and do not penalize revenues of the fishing industry. Considering that a fraction of fish that escape from fishing gear or that are rejected at the sea probably does not survive (unaccounted mortality), it is a major concern for sustainable fisheries management, as unaccounted mortality may lead to biased stock assessment since they will tend to underestimate fishing mortality and overestimate stock size. In this context, in the present Ph.D. thesis, the escape survival (i.e. survival of the fish escaped through the trawl net codend) of the Mullus barbatus Linnaeus 1758 and the discard survival (survival of fish rejected at the sea after being hauled on deck) of Trachurus trachurus were evaluated for the first time in the central Mediterranean Sea. In conclusion, the use of underwater lights in Mediterranean trawl fisheries should be carefully regulated through ad hoc measures that are currently lacking, to minimize the potential impacts of artificial light on some already overexploited stocks. Even if further works should be carried out in the future to test BRDs performances in different areas and seasons, the T90 50 mm codend and the Grid-T45 40 mm seem promising tools to reduce the catch of undersized individuals and contribute to mitigating the current overfishing of Parapenaeus longirostris and Merluccius merluccius. The escape survival of M. barbatus was high and thanks to an improved methodology the bias in the sampling was minimized. However, for improved stock assessment of M. barbatus, the experiment should be repeated to provide accurate escape mortality estimates. While the discard survival of T. trachurus was very low and according to the landing obligation (Reg. EU 1380/2013) all the juveniles of the species should be landed
Dodatni nalaz rasprostranjenosti Seriola fasciata (Carangidae) u Sredozemnom moru
An additional record of the non-indigenous species (NIS) Seriola fasciata from the southern coast of Sicily (Central Mediterranean Sea) is here described in this note. The catch record is the first in the area and confirms the key role of the area for NIS spreading. In addition, an updated map of its spatial distribution is provided as well as a discussion on the possible misidentification and competition with the native greater amberjack Seriola dumerili.U ovoj je bilješci opisan dodatni nalaz o vrsti Seriola fasciata s južne obale Sicilije (Sredozemno more). Ovaj nalaz je prvi na tom području i potvrđuje ključnu ulogu područja za širenje stranih vrsta (NIS). Osim toga, prikazana je ažurirana karta prostorne raspodjele vrste Seriola fasciata, kao i rasprava o mogućoj pogrešnoj identifikaciji i kompeticiji s vrstom Seriola dumerili
Lipid oxidation kinetics of ozone-processed shrimp during iced storage using peroxide value measurements
In this research, in situ generated ozone exposure/wash cycles of 1, 3, and 5 min applied to shrimp samples either before (BIS) or during iced storage (DIS) has been used to study the lipid oxidation kinetics using the peroxide values (PV). The induction period (IP) as well as PV at end of the IP (PVIP) have been obtained. The rate constants (k) as well as half-lives (t1/2) of hydroperoxides formation for different oxidation stages were calculated. The results showed that both IP and PVIP were lower with BIS (IP between 4.35±0.09 and 5.08±0.23 days; PVIP between 2.92±0.06 and 3.40±0.18 mEq kg−1) compared with DIS (IP between 5.92±0.12 and 6.14±0.09 days; PVIP between 4.49±0.17 and 4.56±0.10 mEq kg−1). The k value for DIS seemed to be the greater compared to BIS. In addition, whilst decreases and increases in t1/2 were found at propagation, respectively, for BIS and DIS, decreases and increases were only found at the induction of oxidation stage(s) for BIS. Further, the PV of ozone-processed samples would fit first order lipid oxidation kinetics independent of duration of ozone exposures. For the first time, PV measurements and fundamental kinetic principles have been used to describe how increasing ozone exposures positively affects the different oxidation stages responsible for the formation of hydroperoxides in ozone-processed shrimp
A Tale on the Demersal and Bottom Dwelling Chondrichthyes in the South of Sicily through 20 Years of Scientific Survey
In the present work, an overview of the demersal (sharks‐chimaera) and bottom dwelling (batoids) of experimental survey international bottom trawl survey in the mediterranean (MEDITS) data, from 1994 to 2013, is provided. The analysed data refer to a wide area located off the southern coast of Sicily, namely south of Sicily (according to the general fisheries commission for the mediterranean (GFCM) classification, Geographical Sub‐Area 16). A checklist of the recorded Chondrichthyes was integrated by density index, D.I. (N/Km2) and average individual weight (as the ratio between biomass index, D.I. (N/Km2) and D.I.). Results suggest that most of the Chondrichthyes in South of Sicily are in a steady state, although in the last few years, they seemed to recover. The spatial distribution of sharks‐chimaera in the geographical sub‐area (GSA) 16 is mainly concentrated in the southern and north‐western zones. Nevertheless, possible management actions to promote the recovering of these very important ecological and threatened species are discussed
Prvi nalaz mača srebrenjaka Trachipterus trachypterus Gmelin 1789 (Lampriformes) u Sicillijanskom tjesnacu
On July 7th 2018 a specimen of Mediterranean dealfish (Trachipterus trachypterus Gmelin 1789)
was caught in the shallow waters of Selinunte (in the South-Western coast of Sicily) by trammel net.
It was a female in maturing phase and the gonadosomatic index resulted as 1.1%. The specimen
measured 1638 mm in total length and weighed about 2480 g. The estimated age through growth
increments in vertebra was of 41 years. The finding of the Mediterranean dealfish in the Strait of
Sicily might be linked to its spawning period during which it approaches the shallow waters. The
present specimen represents the first record in the Strait of Sicily.Dana 7. srpnja 2018. uzorak mediteranskog dealfish (Trachipterus Trachypterus Gmelin 1789) je
uhvaćen u plitkim vodama primorskog mjesta Marinella di Selinunte (na jugozapadnoj obali Sicilije)
s troslojnom mrežom. Bila je to ženka u fazi sazrijevanja, a gonadosomatski indeks rezultirao je
1,1%.
Uzorak je izmjeren 1638 mm ukupne duljine i težio je oko 2480 g.
Procijenjena dob kroz povećanje rasta kralježaka bila je 41 godinu. Otkrivanje mediteranskog
delfish u Sicilijskoj tjesnac mogao bi biti povezan s njegovim razdobljem mrijesta tijekom kojeg se
približava plitkim vodama. Sadašnji uzorak predstavlja prvi zapis u Siciliji
Escape Survival and Scale Damage Assessment of Red Mullet (Mullus barbatus Linnaeus, 1758) during Bottom Trawling in the Central Mediterranean Sea
Stock assessments routinely evaluate the status of commercially harvested species, but
seldom account for the possible mortality of released or escaping fish. This study presents a method
for estimating the escape survival of the red mullet (Mullus barbatus) from demersal trawling in the
Central Mediterranean Sea. Fish escaping from the trawl codend were collected in a detachable cage,
which was lined to reduce water flow and protect the sampled fish from further fatigue and injury.
Control fish (from an open codend) showed high survival, 94% (87–97%, 95% Confidence Interval),
and minimal injuries, while fish escaping through codend meshes had significantly increased injuries
and reduced survival, 63% (55–70%). During 7 days of captive monitoring, treatment group mortality
was highest in the first 24 h and ceased for both groups within 48 h. Conflicting length-related
mortality was observed, where larger treatment fish had a higher probability of dying, while the
opposite was observed in the controls. Analysis showed that treatment fish were significantly more
injured than control fish, with treatment fish predominantly injured in the head zone. In conclusion,
this improved methodology should be repeated to provide accurate escape mortality estimates for
the improved stock assessment of the red mullet in the Central Mediterranean
Length-Weight Relationships of 52 Species from the South of Sicily (Central Mediterranean Sea)
The Length-Weight relationships (LWRs) of 52 species (14 never reported before) of fishes, crustaceans and cephalopods living on the shelf and upper slope off Southern Sicily are provided. Data were collected in the framework of the International bottom trawl survey in the Mediterranean (MEDITS) in the South of Sicily (Central Mediterranean), covering a time frame ranging from 2012 to 2019. Linear regressions were significant for all species (p < 0.05) with R-2 values ranging from 0.86 to 0.99. The intercept (a) of LWRs ranged from 0.0003 to 0.4677, while the slope (b) ranged from 2.1281 to 3.306. The Welch t-test, used to evaluate differences between the obtained LWRs with those reported in the literature, revealed that most of the LWRs (about 55%) reported in this study are in disagreement with those obtained previously by other authors from the Strait of Sicily. It is expected that the results obtained from this study will contribute to filling the knowledge gap of fish populations in this area and also assist fisheries scientists in future stock assessment studies
British sharks in Sicily: records of long distance migration of tope shark (Galeorhinus galeus) from North-eastern Atlantic to Mediterranean Sea.
The study reports information about the recapture of two tagged adult females of tope shark, Galeorhinus galeus (Linnaeus 1758), in the central Mediterranean Sea (south coasts of Sicily) in 2014 and 2017. The two females were tagged in North-East Atlantic, respectively in Scotland in 2009 and Ireland in 2015. The Scottish specimen was a 175 cm female increasing of about 10 kg in body weight and 37 cm in total length during its 1967 days at liberty (5.39 years). The Irish one, was a pregnant female of an estimated age of 15-17 year which spent 248 days at liberty increasing 14 cm during this period. The growth rate of the two specimens was therefore between 6.8 and 7.8 cm year-1, faster than the annual increments of adults suggested in previous studies. Previous tope recapture records in the Mediterranean Sea were limited to the Alboran Sea, coast of Valencia and the Algerian coasts. The two tope females recaptured in the Strait of Sicily provided the first evidence of long distance entrance of NE Atlantic tope in the Mediterranean Sea. The well known occurrence of mature females and juveniles in this area of the Mediterranean suggest the hypothesis of a migration of adults female from their feeding grounds in north eastern Atlantic to lower latitudes up to the Mediterranean Sea for parturition
Exploring the feasibility of technological transfers of two by-catch reduction devices in the crustacean bottom trawling of the central Mediterranean
Introduction: Most Mediterranean fish stocks are overexploited owing to high
fishing efforts and poor exploitation patterns. Demersal trawl fisheries are
considered the most impactful fishery type because of the high quantities of
unwanted catch that is then routinely discarded at sea.
Methods: In the present study, two types of by-catch reduction devices (BRDs),
that is a sorting grid (Grid-T45 40 mm) and a T90 50 mm codend, were
compared to a typical commercial bottom trawl net (control) in terms of size
structures and catch per unit effort to assess the effect of gear modification on
the selectivity of crustacean fisheries in the central Mediterranean Sea. In
particular, three randomly selected trawlers were involved in a paired hauls
experiment fishing at the same time in the same fishing ground. Each trawler
carried out four hauls per day during a 3-day campaign for a total of 36 hauls. The
target species of the fishery is Parapenaeus longirostris (herein DPS), and the
main commercial by-catch is Merluccius merluccius (herein HKE).
Results: The results showed that the landing per unit effort (LPUE) of DPS was
higher for Grid-T45 40 mm net, although it did not differ significantly from that of
the control net. Conversely, the discard per unit effort (DPUE) of the control net
was significantly higher than of both BRD configurations. For HKE, a slightly
higher LPUE was recorded using the T90 50 mm codend compared to that of the
control, but this result was not statistically significant. The lowest DPUE was
found for the T90 50 mm codend, with significant differences compared to that
of the control and Grid-T45 40 mm net. The catch comparison of the size
structures analysed through generalised linear mixed models highlighted that the
Grid-T45 40 mm net was more effective in catching adult DPS, whereas the T90
50 mm codend was more selective for adult HKE
Discussion: In conclusion, although further studies should be carried out in
future to test the performance of the BRDs in different areas and seasons, the
investigated gear seems to be promising for reducing the catch of undersized
individuals and contributing to mitigating the current overfishing of DPS and HK
Pojava dviju rijetkih vrsta iz reda Lampriformes: britke jedroglavke Lophotus lacepede (Giorna, 1809) i vlasuljke Zu cristatus (Bonelli, 1819) kod sjeverne obale Sicilije, Italija
The bony fish Lophotus lacepede (Giorna, 1809) and Zu cristatus
(Bonelli, 1819) are the two species rarely recorded within the Mediterranean basin, usually reported as accidentally captured
in depth (mesopelagic) fishing operations. In the current work, we present the first record of L. lacepede and Z. cristatus in fishing catches from southwestern Tyrrhenian Sea. Moreover, in order to improve existent biological/ecological knowledge, some bio-related aspects such as feeding aspect, sexual maturity and age estimate have been discussed.Koštunjičave ribe Lophotus lacepede (Giorna, 1809)i Zu cristatus (Bonelli, 1819) dvije su vrste koje se rijetko nalaze u Sredozemnom moru i najčešće su zabilježene kao slučajni ulov pri ribolovu
dubinskim alatima (mezopelagijal). U ovom radu predstavljamo prvi zapis britke jedroglavke i vlasuljke koje su uhvaćene tijekom ribolova u jugozapadnom dijelu Tirenskog mora. Štoviše, kako
bi se poboljšalo postojeće znanje o biologiji i ekologiji, u radu se raspravlja o nekim biološkim određenim aspektima kao što su prehrana, spolna zrelost i procjena starosti
- …