21 Smooth-hounds in the Northeast Atlantic Reports/Expert Group...Smooth-hounds are also a...

566 | ICES WGEF REPORT 2013

21 Smooth-hounds in the Northeast Atlantic

21.1 Stock distribution

Three species of smooth-hound (Triakidae) occur in the ICES area. The most frequent species in the northern part of the area is starry smooth-hound Mustelus asterias. Common smooth-hound Mustelus mustelus may also occur in northern European seas, although separating these two species on the presence or absence of spots is unreliable (Compagno, 1984; Farrell et al., 2009), and information and data referring to M. mustelus likely refers to M. asterias.

A third species, black-spotted smooth-hound Mustelus punctulatus, occurs in the Med-iterranean Sea (Quignard, 1972) and off NW Africa and may occur in the southern-most part of ICES Division IXa.

M. asterias appears to be the dominant smooth-hound in northern European waters.

Given the problems in separating M. asterias and M. mustelus and that data for these two species are confounded, data in this chapter are generally combined at genus level.

In the absence of dedicated scientific studies on stock units, WGEF considers there to be a single management unit of Mustelus asterias in the continental shelf waters of the ICES area, comprising ICES Subareas IV, VI–IX. This stock may extend to the north-ern part of the CECAF area and possibly the Mediterranean Sea.

Improved studies to better understand the stock unit(s) are required. There are sever-al programmes that tag and release M. asterias in the North Sea and Celtic Seas ecore-gions, and analyses of these data are required. Additionally, tagging studies from the southern parts of the ICES area could be usefully undertaken.

21.2 The fishery

21.2.1 History of the fishery

Smooth-hounds are taken as a seasonal bycatch in trawl, gillnet and longline fisher-ies. Though they are discarded in some fisheries, other fisheries land this bycatch, depending on market demands.

Smooth-hounds are also a relatively important species for recreational sea anglers and charter boat fishing in several areas, with anglers and angling clubs often having catch-and-release protocols.

21.2.2 The fishery in 2012

There were no major changes to the fishery noted in 2012. Information from the fish-ing industry suggests that the increased landings of smooth-hounds are partly to supply market demand for ‘dogfish’ given the current restrictions on spurdog.

21.2.3 ICES Advice applicable

ICES first provided advice for this stock in 2012. Based on ICES approach to data-limited stocks, ICES advises that catches should be reduced by 4%. Because the data for catches of smooth-hounds are not fully documented and considered highly unre-liable (due to the historical use of generic landings categories), ICES is not in a posi-tion to quantify the result.

ICES WGEF REPORT 2013 | 567

21.2.4 Management applicable

EC Council Regulations 850/98 for the `conservation of fishery resources through technical measures for the protection of juveniles of marine organisms’ details the minimum mesh sizes that can be used to target fish. Although other dogfish (Squalus acanthias and Scyl;iorhinus spp.) could be targeted in fixed nets of 120–219 mm and >220 mm mesh size (in regions 1 and 2), Mustelus spp. would be classed under ‘all other marine organisms’, and so can only be targeted in fixed nets of >220 mm. This has been queried by some fishermen.

21.3 Catch data

21.3.1 Landings

No accurate estimates of catch are available, as many nations that land smooth-hounds report an unknown proportion of landings in aggregated landings categories (e.g. dogfish and hounds). Preliminary values of landings are given in Table 21.1 and Figure 21.1.

21.3.2 Discards

Although some discards information is available from various nations, data are lim-ited for most nations and fisheries. Preliminary analyses have indicated that juveniles are typically discarded (Figure 21.2), although the survival of these discards has not yet been evaluated (Silva et al., 2013 WD).

Smooth-hounds taken by beam trawl and Nephrops trawl were composed primarily of juveniles and sub-adults (<70 cm), and most these were nearly all discarded. Gillnet catches were comprised primarily of fish in the 60–110 cm length range, with fish <55 cm usually discarded. Otter trawl catches covered a broad length range, and smooth-hounds <50 cm were typically discarded. The absence of full retention at length in these gears may be due to various factors, such as catch quality and local market value, influencing the discarding behaviour of fishers. Silva et al. (2013 WD) noted that a greater proportion of smooth-hounds were retained since landings of spurdog had become restrictive.

21.3.3 Quality of catch data

Catch data are of poor quality, as much of the landings data have been reported un-der generic landings categories, especially historically. Most nations have made ef-forts to improve the recording of species in recent years.

The availability and quality of catch data for off NW Africa and the Mediterranean needs to be investigated.

Better estimates of discarding are required, with information on discard survival also needed, as a proportion of discarded smooth-hounds may survive.

Biological data are not collected under the Data Collection Regulations, although some generic biological data are available (see Section 21.7).

21.4 Commercial catch composition

Studies to better understand both the species, size and sex composition are required. Given the potential for sexual and sex-based segregation of Mustelus spp., appropri-


ate monitoring would be required to understand the catch composition over appro-priate spatial and temporal scales.

21.5 Commercial catch–effort data

No data available.

21.6 Fishery-independent information

21.6.1 Availability of survey data

Several fishery-independent surveys operate in the stock area. Larger individuals are not sampled effectively in beam trawl surveys (because of low gear selectivity). They are often caught in GOV trawl and other otter trawl surveys in the area. For further details of trawl surveys in the stock area, see Section 15 (North Sea ecoregion), Section 18 (Celtic Seas) and Section 19 (Biscay-Iberia). Summary details from the most recent IBTS are shown in Figure 21.3 and in the Supplementary Information of this section.

Analyses of survey data need to be undertaken with care, as smooth-hounds are rela-tively large-bodied species (maximum size of M. mustelus is about 165 cm total length) and adults are strong swimmers. Hence, larger individuals may not be sam-pled effectively in IBTS surveys. Given their aggregating nature, some surveys may have a large number of zero hauls and a few hauls with relatively large numbers.

Although two species of smooth-hound have been reported in most surveys, the dis-crimination of these species has usually been based on the presence or absence of spots, which is not a reliable characteristic. WGEF consider that survey data for these two species should be combined in any analyses, and that starry smooth-hound Mus-telus asterias is by far the more common of the two species in the Celtic Seas and North Sea ecoregions.

21.6.2 Temporal trends in relative abundance

In the Celtic Sea, the UK PHHT survey demonstrated a peak in the relative abun-dance of Mustelus spp. in 2000. Although this peak was not apparent in the French survey in 2000, this species has also increased in recent years, peaking in 2004 (ICES 2007).

The UK (Northern Ireland) western IBTS Q4 survey of the Irish Sea has also indicated an increase in mean catch rates (ICES, 2010c). The UK(England and Wales) and Irish groundfish survey also catch reasonable numbers of smooth-hounds (see ICES, 2010c, S21.1), and these data should be analysed when more of a time-series has been estab-lished. Larger smooth-hounds, including mature fish, are also taken in these surveys.

The UK(England and Wales) beam trawl survey has also indicated that smooth-hounds are increasing in relative abundance, and are also being observed in an in-creasing proportion of hauls (ICES, 2011; S21.2). The individuals taken in this survey are generally juveniles, and the small proportion of mature fish is due to a low catch-ability.

Although smooth-hounds are not subject to routine biological sampling in any of the surveys, the EngW-WIBTS-Q4 survey tags and releases smooth-hounds, and the in-dividual weights and maturity (of male fish) are recorded prior to release (See Section 21.7.6).


21.7 Life-history information

There have been several biological investigations of Mustelus spp. in European seas, including from the NE Atlantic and Mediterranean Sea.

21.7.1 Reproductive biology

Studies in the Celtic Seas ecoregion have indicated that the total length (and age) at 50% maturity for male and female M. asterias are 78 cm (4–5 years) and 87 cm (six years), respectively (Farrell et al., 2010b).

Estimates of fecundity range from 8–27 (ovarian fecundity) and 6–18 (embryonic fe-cundity), with a gestation period of about twelve months (Farrell et al., 2010b), and there may also be a resting period of a year between pregnancies, giving a 2-year reproductive period.

In the Mediterranean Sea, Mustelus asterias reach maturity at about 75 cm (males) and 96 cm (females), with estimates of fecundity ranging from 10–45 (ovarian fecunddity) and 10–35 (uterine fecundity), with fecundity increasing with length (Capape, 1983).

Studies on Mustelus mustelus in the Mediterranean have found that females matured at 107.5–123 cm total length (50% maturity at 117.2 cm) and that males matured at 88–112 cm (50% maturity at 97.1 cm) (Saidi et al., 2008). This study also found that em-bryonic fecundity ranged from 4–18 embryos, with fecundity increasing with length. Further south, off Senegal, the lengths at first (and 100%) maturities for M. mustelus were found to be 82 cm (95 cm), for males, and 95 cm (104 cm) for females (Capape et al., 2006). This study reported litters of 4–21.

21.7.2 Age and growth

Farrell et al. (2010a) studied the age and growth of M. asterias in the Celtic Seas ecore-gion. Growth parameters for males (n = 106) were L sub( infinity ) = 103.7 cm total length, L sub(0) = 38.1 cm STL, k = 0.195 year super(–1)). Growth parameters for fe-males (n = 114) were (L sub( infinity ) = 123.5 cm STL, L sub(0) = 34.9 cm STL, k = 0.146 year super(–1)). Estimates of longevity were 13 years (males) and 18.3 years (females).

Age and growth of M. mustelus has been studied in South African waters, with males and females estimated to mature at 6–9 and 12–15 years, respectively (Goosen and Smale, 1997). The maximum age reported in this study was 24 years.

The length–weight relationship of Mustelus spp. caught during the Cefas tagging programme, 2000–2010 is illustrated in Figure 21.4.

21.7.3 Habitat

The distribution of Mustelus spp. around the British Isles has been described, with more detailed studies on the habitat utilization only examined in the English Channel (Martin et al., 2010, 2012).

21.7.4 Pupping and nursery areas

Pups of M. mustelus are born at a size of 34–42 cm in the Mediterranean (Saidi et al., 2008) and 36 to 45 cm off Senegal (Capape et al., 2006). Pups are taken in trawl sur-veys, and such data might be able to assist in the preliminary identification of general pupping and/or nursery areas. Most of the records for pups recorded in UK beam


trawl surveys are from the southern North Sea (IVc), parts of the English Channel and Bristol Channel (VIIf) (Ellis et al., 2005).

The lack of more precise data on the location of pupping and nursery grounds, and their importance to the stock, precludes spatial management for this species at the present time.

Studies on other species of smooth-hound have shown high site fidelity of immature individuals on nursery grounds (Espinoza et al., 2011).

21.7.5 Diet

Mustelus spp. are primarily carcinophagous, predating on a variety of crustaceans, including hermit crabs (Paguridae), stomatopods, brachyuran crabs, squat lobsters and shrimps, with teleosts also consumed by larger individuals (Ellis et al., 1996; Morte et al., 1997; Jardas et al., 2007; Santic et al., 2007; Saidi et al., 2009; Lipej et al., 2011). In some rocky areas they can be important predators of small edible crab Can-cer pagurus.

21.7.6 Movements and migrations

Although the movements and migrations of smooth-hounds are not fully known, there have been relatively high numbers of Mustelus spp. tagged and released during various other elasmobranch research programmes in the UK (Burt et al., 2013 WD), Figure 21.5.

A Dutch angler-led programme has tagged 746 smoothhounds since 2011, with 15 returns so far (Figure 21.6).

Further analyses of these and other data are still required.

21.8 Exploratory assessment models

21.8.1 Previous studies

No previous assessments of NE Atlantic smooth-hounds have been made. However, there have been assessment methods developed for the Australian species Mustelus antarcticus (e.g. Xiao and Walker, 2000; Pribac et al., 2005) which may be applied to European species when relevant data are available.

21.8.2 Data exploration and preliminary modelling

Although no modelling or quantitative stock assessments have been undertaken, trends in relative abundance have been used to inform on current status (see Section 21.6).

21.8.3 Stock assessment

No assessment was undertaken, as a consequence of insufficient data.

21.9 Quality of the assessment

No assessment was undertaken, as a consequence of insufficient data.

Scientific trawl surveys provide the longest time-series of species-specific data.


21.10 Reference points

No reference points have been proposed for this stock.

21.11 Conservation considerations

The IUCN Red List Assessments do not identify smooth-hounds as high conservation importance, listing them as Least Concern (M. asterias and M. mustelus) and Data Deficient (M. punctulatus).

21.12 Management considerations

Smooth-hounds appear to be increasing in relative abundance in trawl surveys, and also in commercial landings data. Given the potential expansion in fisheries for smooth-hounds (which may reflect an increased abundance and that fishing oppor-tunities for S. acanthias are limited), further work to examine this stock is required.

It should be noted that smooth-hounds taken by beam trawl and Nephrops trawl were composed primarily of juveniles and sub-adults (<70 cm), and these were nearly all discarded, as were smooth-hounds <50 cm in the otter trawl fishery (Figure 21.2. Dis-card mortality is not known, and nor is the proportion of recruits that may survive to maturity and marketable size. Further study on the mortality and survivor rates of juveniles in these fisheries are needed to evaluate impacts on recruitment.

Smooth-hounds are also an important target species in some areas for recreational fisheries; though there are insufficient data to examine the relative economic im-portance of these fisheries, or the degree of mortality.

Other species of smooth-hound are targeted elsewhere in the world, including Aus-tralia/New Zealand and South America. Although smooth-hounds are generally quite productive stocks (at least for elasmobranchs), evidence from these fisheries suggests that various management controls can be used for their appropriate management.

21.13 References Burt, G. J., Silva, J. F., McCully, S. R., Bendall, V.A. and Ellis, J. R. 2013. Summary results from

opportunistic tagging programmes for smooth-hound Mustelus spp., greater-spotted dog-fish Scyliorhinus stellaris and tope Galeorhinus galeus around the British Isles. Working Doc-ument to the Working Group on Elasmobranch Fishes, Lisbon, Portugal, 17–21 June 2013. 12 pp.

Capape, C. 1983. New data on the biological of the reproduction of Mustelus asterias Cloquet, 1821 (Pisces, Pleurotremata, Triakidae) from Tunisian coasts. Vie Et Milieu, 33: 143–152.

Capape, C., Diatta, Y., Diop, M., Vergne, Y. and Guelorget, O. 2006. Reproductive biology of the smoothhound, Mustelus mustelus (Chondrichthyes: Triakidae) from the coast of Sene-gal (eastern tropical Atlantic). Cybium, 30: 273–282.

Espinoza, M., Farrugia, T. J. and Lowe, C. G. 2011. Habitat use, movements and site fidelity of the gray smooth-hound shark (Mustelus californicus Gill 1863) in a newly restored southern California estuary. Journal of Experimental Marine Biology and Ecology, 401: 63–74.

Ellis, J.R., Cruz-Martinez, A., Rackham, B.D. and Rogers, S.I. 2005. The distribution of chon-drichthyan fishes around the British Isles and implications for conservation. Journal of Northwest Atlantic Fishery Science, 35: 195–213.

Farrell, E. D., Clarke, M. W. and Mariani, S. 2009. A simple genetic identification method for northeast Atlantic smoothhound sharks (Mustelus spp.). ICES Journal of Marine Science, 66: 561–565.


Farrell, E. D., Mariani, S. and Clarke, M. W. 2010a. Age and growth estimates for the starry smoothhound (Mustelus asterias) in the northeast Atlantic Ocean. ICES Journal of Marine Science, 67: 931–939.

Farrell, E. D., Mariani, S. and Clarke, M. W. 2010b. Reproductive biology of the starry smooth-hound shark Mustelus asterias: Geographic variation and implications for sustainable ex-ploitation. Journal of Fish Biology, 77: 1505–1525.

Gibson, C., Valenti, S.V., Fordham, S.V. and Fowler, S.L. 2008. The Conservation of Northeast Atlantic Chondrichthyans. Report of the IUCN Shark Specialist Group Northeast Atlantic Red List Workshop. viii + 76pp.

Goosen, A. and Smale, M. J. 1997. A preliminary study of age and growth of the smoothhound shark Mustelus mustelus (Triakidae). South African Journal of Marine Science, 18: 85–91.

Jardas, I., Santic, M., Nerlovic, V. and Pallaoro, A. 2007. Diet of the smooth-hound, Mustelus mustelus (chondrichthyes: Triakidae), in the eastern Adriatic Sea. Cybium, 31: 459–464.

Lipej, L., Mavric, B., Resek, S., Chérif, M. and Capapé, C. 2011. Food and feeding habits of the blackspotted smooth-hound, Mustelus punctulatus (Elasmobranchii: Carcharhiniformes: Triakidae), from the northern Adriatic. Acta Ichthyologica et Piscatoria, 41: 171–177.

Martin C.S., Vaz, S., Ellis, J.R., Coppin, F., Le Roy, D. and Carpentier, A. 2010. Spatio-temporal patterns of demersal elasmobranchs in trawl surveys in the eastern English Channel (1988–2008). Marine Ecology Progress Series, 417: 211–228.

Martin, C.S., Vaz, S., Ellis, J.R., Lauria, V., Coppin, F., and Carpentier, A. 2012. Modelled distri-butions of ten demersal elasmobranchs of the eastern English Channel in relation to the environment. Journal of Experimental Marine Biology and Ecology, 418/419: 91–103.

Morte, S., Redon, M. J. and Sanz-Brau, A. 1997. Feeding habits of juvenile Mustelus mustelus (Carcharhiniformes, Triakidae) in the western Mediterranean. Cahiers de Biologie Marine, 38: 103–107.

Pribac, F., Punt, A. E. Taylor, B. L. and Walker, T. I. 2005. Using length, age and tagging data in a stock assessment of a length selective fishery for gummy shark (Mustelus antarcticus). Journal of Northwest Atlantic Fishery Science, 35: 267–290.

Quignard, J. P. 1972. Note sur les especes mediterraneenes du genre Mustelus (Selachii, Gale-oidea, Triakidae) Rev. Trav. Inst. Peches Marit., Nantes, 36(1): 15–29.

Saidi, B., Bradai, M. N. and Bouain, A. 2008. Reproductive biology of the smooth-hound shark Mustelus mustelus (L.) in the Gulf of Gabes (south-central Mediterranean Sea). Journal of Fish Biology, 72: 1343–1354.

Saidi, B., Enajjar, S., Bradai, M. N. and Bouain, A. 2009. Diet composition of smooth-hound shark, Mustelus mustelus (Linnaeus, 1758), in the Gulf of Gabes, southern Tunisia. Journal of Applied Ichthyology, 25: 113–118.

Santic, M., Nerlovic, V. and Pallaoro, A. 2007. Diet composition of blackspotted smooth-hound, Mustelus punctulatus (Risso, 1826), in the eastern Adriatic Sea. Journal of Applied ichthyol-ogy, 23: 279–281.

Silva, J. F., Ellis, J. R., Catchpole, T. L. and Righton, D. 2013. Bycatch and discarding patterns of dogfish and sharks taken in commercial fisheries around the British Isles. Working Docu-ment to the Working Group on Elasmobranch Fishes, Lisbon, Portugal. 17–21 June 2013. 31 pp.

Xiao, Y. and Walker, T. I. 2000. Demographic analysis of gummy shark (Mustelus antarcticus) and school shark (Galeorhinus galeus) off southern Australia by applying a generalized Lotka equation and its dual equation. Canadian Journal of Fisheries and Aquatic Sciences, 57: 214–222.


Table 21.1. Smooth-hounds in the Northeast Atlantic. Reported species-specific landings (tonnes) for the period 1978–2011. These data are considered underestimates as some smooth-hounds are landed under generic landings categories. Species-specific landings data are not available for the Mediterranean Sea and are limited for northwestern African waters.

1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985

Belgium . . . . . . . . . . . . .

France 0 0 0 0 0 0 32 0 0 222 218 66 143

Netherlands . . . . . . . . . . . . .

Portugal . . . . . . . . . . . .

UK -E, W & NI . . . . . . . . . . . . .

UK - Scotland . . . . . . . . . . . . .

0 0 0 0 0 0 32 0 0 222 218 66 143

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

Belgium

France 64 117 126 93 90 102 138 145 228 187 197 64 117

Netherlands . . . . . . . . . . . . .

Portugal . . . . . . . . . . . . .

UK -E, W & NI . . . . . . . . . . . . .

UK - Scotland . . . . . . . . . . . . .

64 117 126 93 90 102 138 145 228 187 197 64 117


Table 21.1 (continued). Smooth-hounds in the Northeast Atlantic. Reported species-specific landings (tonnes) for the period 1978–2011. These data are considered underestimates as some smooth-hounds are landed under generic landings categories. Species-specific landings data are not available for the Mediterranean Sea and are limited for northwestern African waters.

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

Belgium 8

France . 306 377 585 589 682 767 714 908 522 926 969 706 2695

Netherlands . . . . . . . . . . . 8 3

Portugal . . . . . . . . . . . . 35 32

UK -E, W & NI

. 14 . . . . . . . 115 132 161 919

UK - Scotland

. . . . . . . . . . 1 .

0 320 377 585 589 682 767 714 908 637 1059 1138 1664 2728


Figure 21.1. Smooth-hound in the Northeast Atlantic. Working group estimates of Mustelus spp. landings by country, 1973–2012.

0

500

1000

1500

2000

2500

3000

1973

1976

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1982

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1991

1994

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2009

2012

Year

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ings

(ton

nes) Portugal

Belgium

UK - Scotland

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Netherlands

France


Figure 21.2. Smooth-hounds in the Northeast Atlantic. Length–frequency of discarded and re-tained smooth-hounds Mustelus spp. by (a) otter trawl (2002–2005), (b) otter trawl (2006–2011), (c) gillnet (2002–2005), (d) gillnet (2006–2011), (e) beam trawl (2002–2011) and (f) Nephrops trawl (2002–2011), as recorded in the Cefas observer programme. Data aggregated across ecoregions (Source: Silva et al., 2013 WD).

(a) (b)

(c) (d)

(e) (f)


Figure 21.3a. Smooth-hounds in the Northeast Atlantic. Captures of Mustelus asterias as reported in the 2011 IBTS. The catchability of the different gears used in the NE Atlantic surveys is not constant; therefore the map does not reflect proportional abundance in all the areas but within each survey. (From ICES, 2012).

35

40

45

50

55

60

15 10 5 0 5 10

15 10 5 0 5 10

35

40

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LEGEND

6183060> 70

SURVEYS:NS-IBTSSCOGFSIGFSNIGFS_Q4EN-CEFAS_ASP_PorcEN-CEFAS_BFR-EVHOEFR-CGFSSP_NorthPT-GFSSP_GC

Mustelus aste

3 outliers between 226 and 406


Figure 21.3b. Smooth-hounds in the Northeast Atlantic. Captures of Mustelus mustelus as report-ed in the 2011 IBTS. The catchability of the different gears used in the NE Atlantic surveys is not constant; therefore the map does not reflect proportional abundance in all the areas but within each survey. (From ICES, 2012).

35

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Mustelus mu


Figure 21.4. Smoothhounds in the Northeast Atlantic. Length–frequency distributions of Mus-telus spp. (n = 715), and the length–weight relationships for (Mustelus spp. (n = 508) tagged during the Cefas programme. Source: Burt et al., 2013 WD.

Figure 21.5. Smooth-hounds in the Northeast Atlantic. Locations of smooth-hound, Mustelus spp. (i) released and (ii) release and recapture positions for recaptured fish (2000–2013). Source: Burt et al., WD 2013.


Figure 21.6. Smooth-hounds in the Northeast Atlantic. Recapture positions of smooth-hounds from Dutch sport fishing tagging programme. Source: Niels Breve, Sportvisserij Nederland, pers comm.)


Supplementary material: Mustelus survey summary sheets

S21.1

Species: Smooth-hounds

Survey area: VIIaf

Survey acronym: UK (E&W) VIIAF BTS

Survey gear: 4 m Beam trawl with chain mat

Survey data used:

Mean cpue of VIIaf smooth-hounds. Dashed lines give mean annual cpue for 2005–2009, red line shows mean annual cpue for 2010–

2011.

Distribution and relative abundance of smooth-hounds in survey area (from Ellis, 2010).

Length distribution of smooth-hounds in

beam trawl survey for the periods 2005–2009 and 2010–2011.

Distribution: Most abundant in the Bristol Channel and St George’s Channel, although occasionally recorded in the northern parts of the Irish Sea.

Catch rates: Increasing.

Size distribution: Larger fish poorly sampled by the gear, so these data will not inform on the size distribution of the overall stock. In contrast, juveniles (including neonatal specimens with fresh umbilical scars) are captured, which may help with the identifi-cation of potential nursery grounds.

Overall status: Although the large size of this species means that adults are not sam-pled effectively in current surveys, stock status appears healthy.

Exploitation: It is considered that the current levels of exploitation are appropriate for the stock.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

Mea

n CP

UE

(ind/

h)

-8 -7 -6 -5 -4 -350.0

50.5

51.0

51.5

52.0

52.5

53.0

53.5

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54.5

55.0

0

10

20

30

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60

20 30 40 50 60 70 80 90 10

Freq

uenc

y

Total length (cm)

Mustelus spp.

3-7 yrs Last two years


S21.2

Species: Smooth-hounds

Survey area: IVc, VIId

Survey acronym: UK (BTS-Q3)

Survey gear: 4 m Beam trawl with chain mat

Survey data used:

Mean cpue of IVc–VIId smooth-hounds. Dashed lines give mean ± 1SD annual cpue for 2005–2009, red line

shows mean annual cpue for 2010–2011.

Distribution and relative abundance of smooth-hounds in survey area (from Ellis, 2010)

Length distribution of smooth-hounds in beam trawl

survey for the periods 2005–2009 and 2010–2011

Distribution: Widespread in coastal waters of the survey area, although these catches are comprised mostly of juveniles. Adults, which may occur in deeper waters, are better sampled in otter trawl sur-veys.

Catch rates: Mean catch rates in the last two years are amongst the highest in the time series, and the longer term trend has increased consistently.

Size distribution: Catches comprised mostly of immature fish, and although the survey may inform on younger age classes, the data for adult fish will be more limited (although these may be sampled by the French Channel GFS).

Overall status: Catch rates increasing and population appears healthy.

Exploitation: It is considered that current exploitation is appropriate for the stock.

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1993

1994

1995

1996

1997

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2005

2006

2007

2008

2009

2010

2011

Mea

n ca

tch

per u

nit e

ffort

(ind

/h)

-3 -2 -1 0 1 2 349.0

49.5

50.0

50.5

51.0

51.5

52.0

52.5

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010203040506070

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