Stock Assessment Form of MUT (M. barbatus) in combined GSA 15-16 Reference year: 2015 Reporting year: 2006-2015 Red mullet, Mullus barbatus, is an important species commercial for demersal fisheries in the Strait of Sicily (GFCM- GSAs12-16, south-central Mediterranean Sea). It is fished almost exclusively by bottom trawling on shelf grounds. Based on available knowledge red mullets inhabiting the continental shelf of GSA 15 and 16 are considered as a stock unit with average annual landings for the period 2006-2015 of about 774 tons. Italian trawlers catch about 95% of the total production of red mullet in the area, being a yield of Maltese trawlers about 5%. Trawl fishery data for the period 2006-2015 have been used to assess the Mullus barbatus stock in the combined GSA 15 and 16. The assessment was performed by extended survivor analysis (XSA) using commercial catch at age tuned with MEDITS data and FLR routines. The stock resulted in overfishing (F curr >F 0.1 ), with the survey data (MEDITS) time series indicated a relative low biomass of the stock in 2015.
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Stock Assessment Form of MUT
(M. barbatus)
in combined GSA 15-16 Reference year: 2015
Reporting year: 2006-2015
Red mullet, Mullus barbatus, is an important species commercial for demersal fisheries in the Strait of Sicily (GFCM-GSAs12-16, south-central Mediterranean Sea). It is fished almost exclusively by bottom trawling on shelf grounds. Based on available knowledge red mullets inhabiting the continental shelf of GSA 15 and 16 are considered as a stock unit with average annual landings for the period 2006-2015 of about 774 tons. Italian trawlers catch about 95% of the total production of red mullet in the area, being a yield of Maltese trawlers about 5%. Trawl fishery data for the period 2006-2015 have been used to assess the Mullus barbatus stock in the combined GSA 15 and 16. The assessment was performed by extended survivor analysis (XSA) using commercial catch at age tuned with MEDITS data and FLR routines. The stock resulted in overfishing (Fcurr>F0.1), with the survey data (MEDITS) time series indicated a relative low biomass of the stock in 2015.
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Stock Assessment Form version 1.0 (January 2014)
Uploader: Giacomo Milisenda
Stock assessment form
1 Basic Identification Data .............................................................................................................. 2
2 Stock identification and biological information ........................................................................... 5
2.1 Stock unit ............................................................................................................................... 5
2.2 Growth and maturity ................................................................................................................. 6
3 Fisheries information ................................................................................................................... 8
3.1 Description of the fleet ......................................................................................................... 8
and musky octopuses), and Lophius spp. (anglerfish). Red mullet is fished almost exclusively by trawling
on shelf bottoms. Based on available knowledge red mullets inhabiting the continental shelf of GSA 15
and 16 are considered as a stock unit with an average annual landings for the period 2006-2015 of about
774 tons. Italian trawlers catch about 95% of the total production of red mullet in the area, while
amounting yield of Maltese trawlers is about 5%.
Table 3-1: Description of operational units exploiting the stock
Country GSA Fleet Segment
Fishing Gear
Class
Group of
Target Species Species
Operational
Unit 1* ITA 16
E - Trawl (12-
24 metres) 03 - Trawls
34 - Demersal
slope species MUT
Operational
Unit 2 ITA 16
F - Trawl (>24
metres) 03 - Trawls
34 - Demersal
slope species MUT
Operational
Unit 3 MLT 15
E - Trawl (12-
24 metres) 03 - Trawls
34 - Demersal
slope species MUT
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Table 3.1-3: Catch, and effort by operational unit in the 2015.
Operational Units*
Fleet
(n° of
boats)*
Catch (T or
kg of the
species
assessed)
Other
species
caught
(names and
weight )
Discards
(species
assessed)
Discards
(other
species
caught)
Effort
(units)
ITA 99 E 03 34 -
MUT 394 372.9
ITA 99 F 03 34 -
MUT 14 99.1
MLT 99 E 03 34 -
MUT 22 21
Total 493 No discard
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3.2 Historical trends
Trend in catch of red mullet of the Italian and Maltese trawl fleets since 2006 is shown in Fig. 3.2.1. The nominal effort (KW*days at sea) shows a decreasing of the two segments of the Italian trawl fleet (LOA<24m and LOA >24m) since 2004 (Fig. 3.2.2).
Figure 3.2.1 - Catch of MUT from 2005 to 2014 in the Strait of Sicily, Central Mediterranean (GSA
15 and 16) by fleet (Italian and Maltese trawlers).
Figure 3.2.2 – Fishing effort from 2004 (Italy) – 2005 (Malta) to 2014 in the Strait of Sicily, Central
Mediterranean (GSA 15 and 16) by fleet distinguished by country and LOA.
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Figure 3.2.3 – Length frequency distributions mean (LFD) by fleet and country, combined sex.
3.3 Management regulations
As in other areas of the Mediterranean, the stock management of Italian fleet is based on control of
capacity (number of fishing licenses), fishing effort (days at sea, number of trawls), and technical
measures (cod-end mesh size, area closures and fish-size limits). A medium term management plan for
2008-2013 has been agreed for Italian trawlers in the Strait of Sicily. the plan was mainly based on a fleet
reduction of 25% of the capacity obtained in two steps. The first (12.5%) from 2008 to 2010, and the second
(12.5%) from 2011 to 2013. A trawling ban of 30 day per year oriented to retard the recruitment to fishery of
red young of the year is adopted in late summer early autumn.
In addition, the Mediterranean Regulation EC 1967 of 21 December 2006 fixed a minimum harvest size of 11
cm TL for Mullus spp. and a minimum mesh size of 40 mm square or 50 mm diamond for EU bottom trawling
vessels (i.e. Italian and Maltese trawlers).
In 2015, Malta had 14 trawlers that operated on a full-time basis. A preliminary analysis of the capacity of the
fleet in the Sub-regional Committee report for the Central Mediterranean (SRC_CM) showed that there was a
39% reduction from 2011 to 2015 (7 permanent and 2 temporary). Fishing effort and capacity in the 25 nautical
miles fisheries management zone are being managed by limiting vessel sizes, as well as total vessel engine
powers (EC 813/2004; EC 1967/2006). Trawling is allowed within this designated conservation area, however
only by vessels not exceeding an overall length of 24m and only within designated areas. Such vessels fishing
in the management zone hold a special fishing permit in accordance with Article 7 of Regulation (EC) No
1224/2009, and are included in a list containing their external marking and vessel's Community fleet register
number (CFR) to be provided to the Commission annually by the Member States concerned (EC 813/2004).
0
5
10
15
20
25
0
500
1000
1500
2000
2500
3000
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Nu
mb
er in
divid
uals fro
n M
alta (in th
ou
sand
)
Nu
mb
er
of
ind
ivid
ula
s (i
n t
ho
usa
nd
)
TL (cm)
Mean 2006-2015_Italy
Mean 2009-2015_Malta
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3.4 Reference points
Table 3.4-1: List of reference points and empirical reference values in 2015.
Indicator
Limit
Reference
point/empiri
cal reference
value
Value
Target Reference
point/empirical
reference value
Value Comments
B
SSB
F F0.1 0.45
Y
CPUE
Index of
Biomass at
sea
12.2 4.2 24.6
4 Fisheries independent information
4.1 MEDITS TRAWL SURVEY
In order to collect fisheries independent data, which is a requirement of the EU DCF
Final Diagnosis The ratio Fcurr/F0.1 is equal to 1.22 (F0.1 = 0.45), the stock is in low
overexploitation with relative low biomass.
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8 Explanation of codes
Trend categories
1) N - No trend 2) I - Increasing 3) D – Decreasing 4) C - Cyclic
Stock Status
Based on Fishing mortality related indicators
1) N - Not known or uncertain – Not much information is available to make a judgment; 2) U - undeveloped or new fishery - Believed to have a significant potential for expansion in
total production; 3) S - Sustainable exploitation- fishing mortality or effort below an agreed fishing mortality or
effort based Reference Point; 4) IO –In Overfishing status– fishing mortality or effort above the value of the agreed fishing
mortality or effort based Reference Point. An agreed range of overfishing levels is provided;
Range of Overfishing levels based on fishery reference points
In order to assess the level of overfishing status when F0.1 from a Y/R model is used
as LRP, the following operational approach is proposed:
• If Fc*/F0.1 is below or equal to 1.33 the stock is in (OL): Low overfishing
• If the Fc/F0.1 is between 1.33 and 1.66 the stock is in (OI): Intermediate overfishing
• If the Fc/F0.1 is equal or above to 1.66 the stock is in (OH): High overfishing
*Fc is current level of F
5) C- Collapsed- no or very few catches;
Based on Stock related indicators
1) N - Not known or uncertain: Not much information is available to make a judgment 2) S - Sustainably exploited: Standing stock above an agreed biomass based Reference Point; 3) O - Overexploited: Standing stock below the value of the agreed biomass based Reference
Point. An agreed range of overexploited status is provided;
Empirical Reference framework for the relative level of stock biomass index
• Relative low biomass: Values lower than or equal to 33rd percentile of biomass index in the time series (OL)
• Relative intermediate biomass: Values falling within this limit and 66th percentile (OI)
• Relative high biomass: Values higher than the 66th percentile (OH)
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4) D – Depleted: Standing stock is at lowest historical levels, irrespective of the amount of fishing effort exerted;
5) R –Recovering: Biomass are increasing after having been depleted from a previous period;
Agreed definitions as per SAC Glossary
Overfished (or overexploited) - A stock is considered to be overfished when its abundance is below
an agreed biomass based reference target point, like B0.1 or BMSY. To apply this denomination, it
should be assumed that the current state of the stock (in biomass) arises from the application of
excessive fishing pressure in previous years. This classification is independent of the current level of
fishing mortality.
Stock subjected to overfishing (or overexploitation) - A stock is subjected to overfishing if the fishing
mortality applied to it exceeds the one it can sustainably stand, for a longer period. In other words,
the current fishing mortality exceeds the fishing mortality that, if applied during a long period, under
stable conditions, would lead the stock abundance to the reference point of the target abundance