Surveying black bream, Spondyliosoma
cantharus (L.), nesting sites using
sidescan sonar
Technical Paper
doi:10.3723/ut.30.183 International Journal of the Society for Underwater Technology, Vol 30, No 4, pp 183–188, 2012
K J Collins* and J J Mallinson
Ocean and Earth Science, University of Southampton, National Oceanography Centre,
Southampton SO14 3ZH, UK
Abstract
Black bream, Spondyliosoma cantharus (L.), are summer
visitors to the south and west coasts of the UK, overwintering in deeper waters and migrating inshore to breed from
April to June. Bream are demersal spawners, with the eggs
laid in a nest excavated by the male as it creates a depression in a sandy gravel substrate. To build their nests, male
bream expose bedrock and gravel by using their tails to
remove the surface layer.
The present study, using sidescan sonar and SCUBA
diving, extends the known occurrence of extensive nesting
grounds off the West Sussex coast to the Isle of Wight and
Dorset. The nests are typically circular craters 1–2m wide,
and 5–30cm in depth, which can clearly be seen using sidescan sonar as groups of circular depressions. Several thousands of eggs (1–2mm) are attached to bare rock in the
centre of these structures. All the eggs hatch by July.
The species is valuable and particularly vulnerable to
exploitation by both sport and commercial fishermen during
its nesting season. With no minimum landing size and no
prescription for Total Allowable Catch or the International
Council for the Exploration of the Sea (ICES) stock assessment, they are suitable for protection under spatial planning
measures, such as through the use of marine protected
areas (MPAs).
Keywords: black bream, Spondyliosoma cantharus, SCUBA
diving, sidescan sonar, spawning, fisheries management,
English Channel
1. Introduction
Black bream, Spondyliosoma cantharus (L.), belongs
to the family Sparidae, which has a maximum
length reached of 51cm, though most adult specimens are ~35cm (Wheeler, 1978). In the present
paper, ‘bream’ refers to this species. Adults are silver in colour with blue hints, and may have golden
longitudinal lines, although these are more pronounced in juveniles (Miller and Loates, 1997).
Nesting males are usually almost black in colouration (Dipper, 2001; Carleton, 2009).
* Contact author. E-mail address: [email protected]
Black bream are protogynous hermaphrodites
(Reinboth, 1962), maturing as males at approximately 20cm and remaining male until they reach
30cm. At this length they may change into females,
with any fish over 40cm being female (Pawson,
1995). Mouine et al. (2011) describe the reproductive characteristics of bream, as well as the change
from female to male for a population off Tunisia.
The ecological advantage of sequential hermaphroditism in animals, including Sparidae, is discussed
by Warner (1975).
The species can be found in northeastern Atlantic shelf waters, ranging from Norway and the
­Orkney Islands south into the Mediterranean and
the Canary Islands, and are most plentiful in the
English Channel and south to the Mediterranean
Sea (Wheeler, 1978; Pawson 1995). In the UK,
­Rogers (1998) found the species to be more plentiful along the south coast rather than the North Sea
coast, and in mostly shallower than 15m deep water.
Depth range is 5–300m and the fish may be found
in a variety of habitats including over seagrass
(Zostera marina) beds (Lythgoe and Lythgoe, 1991;
Jackson et al., 2002; Kay and Dipper, 2009) and rocky
or sandy bottoms (Bauchot and Hureau, 1986).
Around the British Isles, bream are generally summer visitors and are found off the south and west
coasts during warm periods. Although some tagging of black bream has been carried out (Pawson,
1995), minimal returns have been recorded, resulting in migration patterns to be inferred from fishery data and analysing the distribution of maturing,
ripe and spent fish.
Adult bream overwinter in deep water (50–100m)
west from Alderney, Nova Scotia, to Start Point,
Devon (Pawson, 1995). As the temperature rises they
migrate east, reaching Sussex in March where they
take to the shallow inshore waters (<5m). It has been
proposed that these migrations follow the eastward
movement of the 9°C isotherm (Pawson, 1995).
During April they usually move into an area off the
coast of Littlehampton, West Sussex, which has been
183
Collins and Mallinson. Surveying black bream, Spondyliosoma cantharus (L.), nesting sites using sidescan sonar
positively identified as a breeding ground (Carleton,
2009). Spawning in the English Channel occurs May
to June (Perodou and Nedelec, 1980), April to May
(Soletchnik, 1983). Outside of the widely reported
April to May period, Pawson (1995) notes a spawning
recorded in the Baie de Seine during September
and October.
Bream are demersal spawners and the males lay
their eggs in a nest excavated by creating a depression
in a gravel substrate. Juveniles are found inshore
around the Channel Islands, Port en Bessin, the Isle
of Wight and in the Solent, suggesting that they
remain close to their spawning grounds (Pawson,
1995). Young fish remain inshore for between two
and three years, by which point they become
approximately 20cm in length. They are then sexually mature and recruit into the adult population
(Carleton, 2009).
In order to build their nests, male bream use
their tails to remove the surface layer bedrock and
gravel. The process may also be used to attract a
female. The nests themselves tend to be 1–2m wide
and 5–30cm in depth, and can clearly be seen on
sidescan sonar as groups of crater-like depressions.
After an appropriate nest is selected by the female,
she lays a thin layer of eggs within its area, which
the male then fertilises (James et al., 2010).
Surveys for the aggregate industry (Southern
Science 1995; EMU, 2008) identified spawning
grounds on near-shore (~10m depth) sandstone and
chalk reefs between Bognor and Worthing 25–50km
east of the study, as indicated in Fig 1. The presence of nests in this area was further confirmed by
James et al. (2010). Sussex Sea Fisheries District
Committee officers, Dapling and Clark (pers.
comm.), considered this to be a significant find,
and that catch data suggest there were also centres
for breeding south of the Isle of Wight and further
west.
The present study seeks to extend the known distribution of bream nesting sites westward from the
Isle of Wight to Dorset.
2. Methods
Sidescan sonar with integrated GPS was used
(Humminbird 997c Combo) in single-beam mode
at 800kHz, with a swath width of 46m (150ft) to
­survey the study sites shown in Fig 1. This was used
in two modes: (a) snapshot, recording the screen
image (portable PNG format) which was subsequently adjusted for vessel speed and removal of
the water column section of the image, rotated to
match the vessel heading and geo-referenced in
ArcView 8.2; or (b) record, converting the files with
the Son2xtf program from Humminbird SON format to the widely used XTF format. DeepView Publisher 3.0 was used to convert the XTF files to
Google Earth KMZ format. A disadvantage of this
easy-to-use program is that removal of the water
column below the vessel is not possible. The width
of the nest was measured from the crest to crest of
the bank surrounding the depression.
Sites were investigated by SCUBA diving to confirm that nests and eggs were present, plus recorded
by digital cameras and video (Contour high definition (HD) in a waterproof case taped to the
diver’s mask strap). The HD resolution of the video
permitted extraction of acceptable still frames
(Fig 2).
Fig 1: Location of the bream nest study sites off the central south coast of the UK
184
Vol 30, No 4, 2012
Fig 2: Photograph of a diver examining a bream nest on
Southbourne Rough showing bedrock cleared of sandy
gravel by the bream to form a crater 2m across. The inset
shows a detail of eggs (2mm) adhering to the newly exposed
bedrock
3. Results
Sidescan sonar studies described in the present
paper were undertaken in May 2010 (Dorset) and
June 2011 (Sandown Bay), while the diving studies
have been undertaken over the past decade. The
Southbourne Rough bream nesting site was first
studied by the authors and collaborators (Markey
and Baldock) diving in 1990 and reported by
­Collins (2003).
Poole Bay contains a number of low, small patch
reefs (typically <100m across) composed of ironrich sandstones surrounded by silty sand seabed. In
the months of May and June, over many years
bream nest craters (Fig 2) have been found at the
perimeter of these patch reefs where the sediment
cover is thin, enabling the bream to clear to the
bedrock on which a single layer of eggs (2mm
diameter) is laid.
The ability of bream to rapidly excavate sands
and gravels was observed directly in research aquarium display tanks, where a male bream repeatedly
excavated craters 20cm deep and 80cm wide in less
than 30mins by vigorous tail and body wafting of
the substratum. These patch reefs are the focus
of intensive sport angling specifically targeting the
bream from April to June. Diving was difficult at
some of the Poole Bay sites simply because of the
number of angling boats targeting the bream.
The nesting site in the centre of Poole Bay was
revealed by a single speculative sidescan track
across the bay (James et al., 2010), but not investigated as part of that study. This was unexpected as
there are no reef outcrops in this area. Diving in
May 2010 revealed that the seabed sediment is very
mixed with a full range of material: silts, sands,
gravel and shell, cobble and buried boulders. The
bream excavate craters that completely clear subsurface flat boulders typically 0.5–1m wide.
Tanville Ledge is a single 500m-long ridge of
steeply inclined sandstones surrounded by sand.
Fig 3a shows the crest of the ridge (at the top of
the figure) to the flat seabed at the bottom, with
the nests concentrated in a narrow band along the
rock/sand margin. Here the sediment is sufficiently
shallow to allow exposure of the bedrock. At the
Dancing Ledge site there are bands of shallowly
inclined limestone strata with narrow and shallow
sands between ridges. In Sandown Bay the sandstone reef surface is very irregular.
The most extensive occurrence of bream nests
was found off Kimmeridge. Here, there are many
square kilometres of faulted shales producing a
saw-tooth section that has rock ledges interspersed
with pockets of sand/gravel/shell sediment (Brachi
et al., 1978). Fig 3b shows a central low rock ledge
separating two bands of the sediment that have been
extensively excavated. To the right of the figure,
the deeper sediment is formed into sand-waves.
Analysis of the nest crater widths from the processed sidescan images is shown in Fig 4 and Table 1.
Kruskal-Wallis one-way analysis of variance on
ranks of width shows significant difference between
sites (P = <0.0001). The Kimmeridge nests are
(a)
(b)
Fig 3: Sidescan images below vessel to 46m to port (vertical),
70m track (horizontal) showing bream nests at (a) Tanville
Ledge; and (b) Kimmeridge
185
Collins and Mallinson. Surveying black bream, Spondyliosoma cantharus (L.), nesting sites using sidescan sonar
Table 1: Comparison of bream nest width by Mann Whitney Rank Sum Test (P =) showing a number of
samples and depth of sites
depth (m)
n=
Tanville Ledge
Southbourne Rough
Poole Bay
Dancing Ledge
Kimmeridge
Sandown
9
107
23
27
10
70
18
20
23
166
15
31
Tanville
Ledge
Southbourne
Rough
Poole
Bay
Dancing
Ledge
Kimmeridge
Sandown
x
<0.001
x
0.650
<0.001
x
<0.001
0.896
<0.001
x
<0.001
<0.001
<0.001
<0.001
x
0.180
<0.001
0.071
<0.001
<0.001
x
4. Discussion
Fig 4: Average width (±1 standard deviation) of bream nests
at the locations shown in Fig 1
s­ ignificantly larger (using the Mann Whitney Rank
Sum Test, P = <0.001) than at the other study sites.
This is attributed to the wide extent of flat bedrock
with shallow sediment cover. Southbourne Rough
and Dancing Ledge sites are limited by the size of
the reef and the extent of sediment patches, respectively. The steeply inclined strata of Tanville Ledge
further constrain the useable area available to the
bream. Both the central Poole Bay and Sandown
sites are restricted by irregular rock surfaces, boulders and bedrock, respectively.
Over a number of years transparent eggs were
still present in June on the central bare rock at
­several Poole Bay, Southbourne Rough and Sandown Bay nest sites. By July each year no eggs were
observed and it was assumed that they had hatched,
since juvenile specimens were seen swimming
around the reefs.
The circular crater-like nests are readily detectable by sidescan sonar. One salutary lesson was
learned reviewing a recent February sidescan survey from Brixham Harbour. There was a distinct
pattern of circular rings on the seabed. Analysis of
the sonar trace showed these to be less than 1m in
diameter and identical in size. Drop-down video
proved that these were actually scrap car tyres.
186
Each nest contains several thousand eggs representing a valuable food resource which the authors
have observed being exploited by Corkwing (Crenilabrus melops) and Goldsinny wrasse (Ctenolabrus
rupestris). Wilson (1958) describes male bream in
an aquarium driving away intruders until the eggs
have hatched. James et al. (2010) similarly refer to
guarding of the nests by the males. While such
parental care by male Corkwing wrasse (Collins et
al., 1996) and tropical damsel fish has been
observed, close guarding of the bream nests has
not been witnessed. The exhalation bubbles from
diving with open-circuit SCUBA is known to deter
fish, so closed-circuit gear has been used for fish
observation studies to reduce this potential disturbance (Lobel, 2001). Another technique that could
be employed is deployment of a fixed video camera. Lott (pers. comm.) has supplied the authors
with such video of the seabed behaviour of bream
and Spicara maena in the Mediterranean.
Bream are commercially valuable. Pavlidis and
Mylonas (2011) document the rapid growth in
Sparidae aquaculture. Analysis of 1999–2007 landings of black bream for the International Council
for the Exploration of the Sea (ICES) rectangle
30E9 shows that they are mostly to the local ports
of Shoreham and Newhaven. Annual landings have
consistently been ~200 tonnes occurring from April
to June, with a peak in May coinciding with the
spawning season (EMU, 2008).
Bream are not subject to ICES stock assessment or classed as a pressure stock for EU fisheries
management purposes, and no Total Allowable
Catch is prescribed. There is also no minimum
landing size under EU technical regulations, however, as protogynous hermaphrodites this would be
counter-productive. The EU places restrictions on
any towed gear used for sea bream fishing, as it
must have a mesh size >80mm and sea bream must
form a minimum of 70% of the catch (EU, 1998).
This at least protects the juvenile stock.
Vol 30, No 4, 2012
In Sussex bream are targeted by fixed nets
(Cooper, 2005) and pair trawlers, 10–14m length.
In order to gain Marine Stewardship Council (MSC)
certification for the pair trawling bream fishery,
Dapling et al. (2010) concluded that suitable stock
assessments and implementation of associated management measures are required. In addition, the
seabed impacts must be quantified and mitigated.
The vulnerability and limited known extent of
nesting sites suggest that the fish are suitable for
protection under spatial planning measures, including marine protected areas (MPAs). Both the
­Kimmeridge and Dancing Ledge sites are within
proposed Special Area of Conservation (SAC) of
the Studland to Portland (Natural England, 2011),
however, the presence of bream nest sites within
this SAC is not acknowledged. The SAC is part of
the requirements of Natural England, relating to
the conservation of natural habitat types and species through identification of SACs in UK waters
(EU, 2007).
In southeastern England the marine aggregate
industry is more important than in other regions –
a result of land-based supplies being used up and
relatively lower costs for marine transport. The
extraction of marine aggregates is a complex process bringing with it a number of environmental
effects and responsibilities, many of which are poorly
understood, although knowledge is constantly
increasing (Haskoning, 2003; see also ICES, 2000).
Dredging often affects the composition of the
sediment, as coarse material is removed and fine
sediment is deposited. Bream make their nests in
gravel substrates, so if this depositing of fine sediments occurs within an area previously used by the
bream as a nest site, they may consider the area as
unsuitable for further spawning. If alternative sites
are unavailable, then this will clearly negatively
affect the species.
A further problem arises even if changes caused
by dredging are not sufficient to cause abandonment of a nesting site. It is possible that spawned
eggs may be smothered by depositing of sediment.
Although they may be resistant to a certain level of
this as experienced naturally (by storms for example), the increased duration, extent and frequency
of dredging-related depositing may bring further
adverse effects, including the inhibition of embryonic development (Haskoning, 2003).
Climate change appears to be having a positive
effect on bream stocks in the English Channel.
Arkley and Caslake (2004) found that the mean
annual frequency of occurrence of bream off Plymouth has increased with rising sea temperature
from 1913 to 2003. Similarly, the Centre for Environment, Fisheries and Aquaculture Science (Cefas)
eastern English Channel beam trawl survey suggests
an upward trend in bream abundance from 1993 to
2001 (Parker-Humphreys, 2005).
Bream, while aggregated around their nesting
sites, are particularly vulnerable (given the absence
of stock management) to exploitation by both commercial and sport fishing, as well as impact from
aggregate extraction. Special measures should be
considered to protect such regions during the
spawning period. While information on the distribution of nesting sites is limited, sidescan sonar has
proved to be an excellent tool for detecting these
sites, and further surveys to inform fisheries management plans are recommended.
Acknowledgements
The authors wish to thank their fellow divers Mike
Markey and Dr Lin Baldock, who supplied photographs and observations over the past decades. The
boat charter for the sidescan survey was funded by
Dorset Wildlife Trust. Rob Clark and Tim Dapling,
Sussex Sea Fisheries District Committee, supplied
many of the technical reports cited. David Pearce,
University of Bournemouth, analysed the Dorset
sidescan images and undertook a literature review.
Alan Deeming alerted the authors to the presence
of bream in Sandown Bay and supplied his vessel
for the sidescan survey of that site. Christian Lott,
Hydra Institute, Germany, supplied video sequences
from studies in the Mediterranean.
References
Arkley K and Caslake R. (2004). SR568 ‘Off-bottom’ trawling techniques for the sustainable exploitation of nonpressure stocks in Cornish inshore waters. Report by the
Marine Biological Association of the United Kingdom,
Plymouth for the Sea Fish Industry Authority, 89pp.
Bauchot ML and Hureau JC. (1986). Sparidae. In: Whitehead PJP, Bauchot ML, Hureau JC, Nielsen J and Tortonese E. (eds). Fishes of the north-eastern Atlantic and the Mediterranean, vol 2. Paris: UNESCO, 883–907.
Brachi R, Collins K and Roberts C. (1978). A winter survey
of a semi exposed rocky coastline; survey strategy and
field techniques. Progress in Underwater Science 4: 37–47.
Carleton CTL. (2009). Pre-assessment of 26 fisheries to the
MSC standard. The Inshore Fisheries Sustainability Pilot,
Stage 2 Report. Nautilus Consultants, Food Certification
International.
Collins K. (2003). Dorset marine habitat surveys: maerl,
worm reefs, bream nests, sea fans and brittlestars, 2003
survey results. Report to Dorset Wildlife Trust and
­English Nature, 15pp.
Collins K, Jensen A and Mallinson J. (1996). Observations
of wrasse on an artificial reef. In: Sayer M, Treasurer J
and Costello M (eds.). Wrasse: Biology and Use in Aquaculture. Oxford: Blackwell Scientific, 47–54.
Cooper KM. (2005). Cumulative effects of marine aggregate extraction in an area east of the Isle of Wight – A
187
Collins and Mallinson. Surveying black bream, Spondyliosoma cantharus (L.), nesting sites using sidescan sonar
fishing industry perspective. Science Series Technical
Report No. 126. Lowestoft: Cefas, 28pp.
Dapling T, Clark R, Vause BJ, Medley P and Carleton CRC.
(2010). ‘Navigating the future’: developing sustainable
inshore fisheries. The UK Inshore Fisheries Sustainability Project Summary Report. Shoreham-by-Sea. Sussex.:
Sussex Sea Fisheries Committee, 32pp.
Dipper F. (2001). British Sea Fishes, 2nd edition. Teddington,
UK: Underwater World Publications Ltd.
EMU. (2008). Area 435/396 seabed monitoring survey. A
report to Hanson Aggregates Marine Ltd and United
Marine Dredging Ltd. Southampton: Emu Ltd., 31pp and
appendices.
EU. (1998). Provision for fixed gears. Article 11 of Council
Regulation (EC) No. 850/98 of 30 March 1998 for the
conservation of fishery resources through technical measures for the protection of juveniles of marine organisms.
EU. (2007). The EU Interpretation Manual of European
Union Habitats. European Union 142pp.
Haskoning. (2003). Marine Aggregate Environmental
Impact Assessment: Approaching Good Practice. Royal
Haskoning, 342pp.
ICES. (2000). Inshore special area of conservation (SAC):
Studland to Portland pSAC Selection Assessment. Marine
Habitat Committee ICES CM 2000/E:07, 178pp.
Jackson EL, Rowden AA, Attrill MJ, Bossy SF and Jones MB.
(2002). Comparison of fish and mobile macro-­
invertebrates associated with seagrass and adjacent sand
at St. Catherine Bay, Jersey (English Channel): emphasis
on commercial species. Bulletin of Marine Science 71:
1333–1341.
James J, Pearce B, Coggan RA, Arnott SHL, Clark R, Plim JF,
Pinnion J, Barrio Frojan C, Gardiner JP, Morando A, Baggaley PA, Scott G and Bigourdan N. (2010). The South
Coast Regional Environmental Characterisation. London:
British Geological Survey, 249pp.
Kay P and Dipper F. (2009). A field guide to the marine
fishes of Wales and ajacent waters. Llanfairfechan: Marine
Wildlife.
Lobel PS. (2001). Fish bioacoustics and behavior: Passive
acoustic detection and the application of a closed-circuit
rebreather for field study. Marine Technology Society Journal
35: 19–28.
Lythgoe J and Lythgoe G. (1991). Fishes of the sea, the North
Atlantic and Mediterranean. London: Blandford.
188
Miller PJ and Loates MJ. (1997). Collins Pocket Guide: Fish of
Britain and Europe. London: Harper Collins Publishers.
Mouine N, Ktari MH and Chakroun-Marzouk N. (2011).
Reproductive characteristics of Spondyliosoma cantharus
(Linnaeus, 1758) in the Gulf of Tunis. Journal of Applied
Ichthyology 27: 827–831.
Natural England. (2011). Inshore Special Area of Conservation (SAC): Studland to Portland pSAC Selection Assessment. Peterborough: Natural England, 25 pp.
Parker-Humphreys M. (2005). Distribution and relative
abundance of demersal fishes from beam trawl surveys in
the eastern English Channel (ICES division VIId) and
the southern North Sea (ICES division IVc) 1993–2001.
Lowestoft: Cefas.
Pavlidis M and Mylonas CC (eds.) (2011). Sparidae: Biology
and aquaculture of gilthead sea bream and other species.
­London: Wiley-Blackell.
Pawson MG. (1995). Biogeographical identification of English Channel fish and shellfish stocks. Fisheries Research
Technical Report no. 99. Ministry of Agriculture, Fisheries and Food Directorate of Fisheries Research, 72pp.
Perodou J and Nedelec D. (1980). Bilan d’exploitation du
stock de dorade grise. Science et peche, Bull. Inst.Peches
­Maritimes 308: 1–7.
Reinboth R. (1962). Morphologische und functionelle
Zweigeschlechtlichkeit bei marinen Teleostiern (Serranidae, Sparidae, Centracanthidae, Labridae). Zool. Jahrb
69: 405–480.
Rogers SI, Millner RS and Mead TA. (1998). The distribution and abundance of young fish on the east and south
coast of England (1981 to 1997). Science Series Technical Report. Lowestoft: Cefas, 130pp.
Soletchnik P. (1983). Gestion de la dorade grise, elements
de biologie. Oceanis 9: 23–32.
Southern Science. (1995). A study of the black bream
spawning ground at Littlehampton. Report to: United
Marine Dredging, ARC Marine Ltd. and South Coast
Shipping. Hants: Southern Science Ltd.
Warner RR. (1975). The adaptive significance of sequential
hermaphroditism in animals. The American Naturalist 109
(965): 61–82.
Wheeler A. (1978). Key to the fishes of Northern Europe.
London: Frederick Warne Ltd.
Wilson D. (1958). Notes from the Plymouth Aquarium.
J. Mar. Biol. Assoc. UK 37: 299–307.