Journal of Sea Research 65 (2011) 187–194
Contents lists available at ScienceDirect
Journal of Sea Research
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / s e a r e s
A century later: Long-term change of an inshore temperate marine fish assemblage
Matthew McHugh a,b,⁎, David W. Sims a,c, Julian C. Partridge b, Martin J. Genner a,b
a
b
c
Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth, PL1 2PB, UK
School of Biological Sciences, University of Bristol, Bristol, BS8 1UG, UK
School of Marine Science and Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK
a r t i c l e
i n f o
Article history:
Received 19 March 2010
Received in revised form 31 July 2010
Accepted 13 September 2010
Available online 18 September 2010
Keywords:
Long-term change
Coastal fisheries
Overfishing
Community structure
Length-frequency distributions
a b s t r a c t
There is compelling evidence that European marine fish assemblages have undergone extensive changes in
composition over the last century. However, our knowledge of which species have changed in abundance and
body size distributions, and the reasons for these changes, is limited due to a paucity of historical data. Here
we report a study of long-term change in a marine fish assemblage from the inshore waters of the Western
English Channel, near Plymouth. We compiled data from historic trawls undertaken between 1913 and 1922,
and resurveyed those sites in 2008 and 2009. Our results revealed highly significant temporal differences in
assemblage composition, but the scale of change was not consistent among taxonomic groups. Dramatic
changes were recorded within the elasmobranchs, characterised by a reduction in abundance of all skate
(Rajiidae) species, apparent extirpation of the angel shark (Squatina squatina), and large increases in the
abundance of lesser-spotted catshark (Scyliorhinus canicula). By contrast we observed less evidence of change
among ‘flatfishes’ (Pleuronectiformes) or ‘roundfishes’ (other teleosts). Changes were also observed in
length–frequency distributions, with a significant decline in the size distribution of elasmobranchs (excluding
S. canicula), but no significant change in size distributions of either group of teleosts. These data provide
further evidence that larger, slow-maturing species have undergone declines in UK waters over the last
century, and form useful benchmarks for assessment of future changes in this coastal faunal assemblage.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
European coastal fisheries have operated for over 1000 years
(Barrett et al., 2004; Engelhard, 2008), and during this time have
undergone substantial changes in fisheries effort, gears, and target
species (Sen, 1997). One of the most significant developments was the
establishment of commercial trawl fisheries, which first became
widespread in the 1800s and largely replaced near-shore static gear
fisheries by the beginning of the 20th century (Garstang, 1900). One
of the first locations to adopt trawl fisheries was the southwest of
England where they were in widespread use by sail-powered vessels
during the mid to late 18th century (Robinson, 1996). Subsequent
developments of steam and diesel powered vessels increased fisheries
accessibility of both inshore and offshore waters (Engelhard, 2008).
Given the long history of commercial fishing in the SW of England,
there is a need to understand what long-term changes have taken
place, why they may have taken place, and what measures could be
implemented in management initiatives aimed at sustainable fisheries and biodiversity conservation.
⁎ Corresponding author. Marine Biological Association of the United Kingdom, The
Laboratory, Citadel Hill, Plymouth, PL1 2PB, UK. Tel.: +44 1752 633335; fax: + 44 1752
633102.
E-mail address: [email protected] (M. McHugh).
1385-1101/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.seares.2010.09.006
Selective fishing can lead to changes in population parameters
including stock abundance (Jennings et al., 1999; Hutchings and
Reynolds, 2004), age and size structure (Bianchi et al., 2000), growth
rates (Hutchings and Baum, 2005; de Roos et al., 2006), reproductive
age or size (Rochet, 1998), and spatial genetic structure (de Roos et al.,
2006). It is often larger and later maturing species that are the least
resilient to sustained fishing pressure (Jennings et al., 1998), while
non-target species are generally more resistant to the direct effects of
fishing, especially those that mature at smaller sizes relative to
commercial species (Pope et al., 2000; Piet et al., 2009). The effects of
fishing can however cascade to other trophic levels and lead to
indirect responses. For example, since fisheries tend to target large
commercial species, removal of larger individuals can effectively
reduce predation risk to smaller fish leading to increased abundance
of non-target species. Such indirect effects can, at least in theory,
intensify apparent declines in mean trophic levels (i.e. as a result of a
reliance on smaller and short lived species) of assemblages caused by
fishing (Pinnegar et al., 2002). These indirect trophic cascades have
significant ecological effects, for example intensive fishing can
eliminate the predation risk to benthic grazers (e.g. sea urchins)
that in turn regulate the structure of benthic algal assemblages (Sala
et al., 1998). The effects of trophic cascades can also be socioeconomic,
and have led to changes in fishing practices in some regions of the
world. For example, following the collapse of the Atlantic cod (Gadus
morhua) fishery off Nova Scotia, there has been a switch to harvesting
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M. McHugh et al. / Journal of Sea Research 65 (2011) 187–194
benthic macroinvertebrates, namely snow crab (Chionoecetes opilio)
and northern shrimp (Pandalus borealis) (Frank et al., 2005).
There is now considerable evidence that fishing-induced longterm changes have taken place in the fish communities of European
waters. For example, reconstruction of the size structure of Atlantic
cod populations using bones found in middens from ca 2900 BC have
revealed significant declines in body size, consistent with the known
negative effects of commercial fisheries (Limburg et al., 2008).
Analysis of distributional records also shows that some species were
formerly more widespread, and that at least one species, common
skate (Dipturus batis), has been extirpated from a large area of the
European continental shelf including the Irish Sea (Brander, 1981;
Dulvy et al., 2000) and the English Channel (Rogers and Ellis, 2000;
Ellis et al., 2004). Perhaps the strongest evidence of long-term
changes comes from abundance records from historic trawl surveys
(Rogers and Ellis, 2000; Genner et al., 2010a). For example, analyses of
such data from the North Sea have revealed significant declines in size
distributions and abundance of many commercial species that have
been attributed to the effects of overfishing (Rice and Gislason, 1996;
Rijnsdorp et al., 1996).
Coupled with fishing, climatic changes can also have effects on fish
distributions and abundances. Over the last century North Atlantic
mean annual sea surface temperature has risen by approximately 1 °C,
and this change has been suggested to have impacted fish distributions (Perry et al., 2005; Brander, 2007). This regional climate change
has been invoked in driving abundance increases of many smaller and
southern species (Stebbing et al., 2002; Rijnsdorp et al., 2009), for
example red mullet (Mullus surmuletus) and anchovy (Engraulis
encrasicolus) on the European continental shelf (Beare et al., 2004,
2005). It is believed that future warming will continue to shift species
abundances and distributions in line with their thermal tolerance and
ability to adapt ecologically (Harley et al., 2006). Fish often require a
variety of habitats throughout their life history stages (egg, larva,
juvenile and adult), and changes to the environmental conditions at
any of these may affect recruitment and survivorship. However, at
present little is known about the preferred habitat of many species
during all life stages (Hurst, 2007), and thus it is difficult to predict
what effects warmer temperatures will have. In extreme cases,
increasing temperatures may force species from preferred habitats,
leading to extinction (Thomas et al., 2004). Alternatively, fish may
stay longer in habitats that are more thermally suitable, leading to
increased local abundance and wider distributions. Changes in sea
temperature can also alter the spawning times and locations of fish
and invertebrates (Minchin, 1992; Sims et al., 2004; Genner et al.,
2010b), which can potentially determine the strength of recruitment
through a match or mismatch with the timing of prey availability
(Beaugrand et al., 2003). Conversely, there is also the possibility that
larval fish will face a higher risk of predation as predators will
undoubtedly have increased metabolic needs as temperature
increases. Together, these examples suggest that only long-term
studies will enable climatic mechanisms underlying observed changes
to be better understood.
Among the earliest fisheries-independent trawl surveys in European waters were those undertaken by the Marine Biological
Association (MBA) in the Western English Channel near Plymouth.
One of these surveys focussed on the species composition of the
shallow (b20 m depth, chart datum) inshore waters between 1911
and 1922. Such inshore waters are important areas for sampling
because numerous fish species use them during their juvenile stages
(Gibson, 1997), especially commercially-important flatfishes, species
such as plaice (Pleuronectes platessa) and turbot (Psetta maxima).
These species utilise shallow inshore habitats post-settlement, before
dispersing to thermally more stable offshore waters as their dietary
requirements change and the risk of predation reduces with increased
body size (Able et al., 2005). Despite the importance of inshore areas
as nursery grounds, there are relatively few long-term surveys of
inshore grounds compared with the number of offshore surveys (e.g.
Désauany et al., 2006; Tulp et al., 2008; Rogers and Millner, 1996).
Most of the inshore areas (b40 m depth) of the United Kingdom (and
European fishing nations) are utilised by vessels (b12 m) which,
primarily, operate static/passive gear (IFREMER, 2007) i.e. pots,
longlines and static nets, but have the capability of operating trawls.
Inshore grounds are not routinely trawled because of the conflict with
fixed/passive gear i.e. it can be difficult to ascertain the direction of
fixed gears making it difficult to trawl without entanglement.
However, trawling inshore areas provides a quick (as opposed to
fixed gears) method of sampling, and often provides a more precise
picture of fish distribution and habitat (Hayes et al., 1996). Availability
of these data provides an opportunity to explore in this study, by
resurveys of inshore sampling sites near Plymouth, whether changes
observed in inshore waters are congruent with those observed in
offshore waters over the last century.
2. Materials and methods
2.1. Study site
Historic inshore trawls were undertaken between 1911 and 1922
at three locations near Plymouth, namely Cawsand Bay, Whitsand Bay
and Bigbury Bay (Fig. 1). Both Cawsand and Bigbury bays are under
the jurisdiction of the Devon sea fisheries committee while Whitsand
Bay is under Cornwall sea fisheries committee. The survey sites have
water depths less than 20 m, and were within 1 km of the coast.
Contemporary resurveys were undertaken during 2008 and 2009 at
two of these sites (Whitsand Bay and Bigbury Bay); while Cawsand
Bay was excluded as it is now a mooring location for naval ships and
privately owned craft. Both of the contemporary sites face south to
south-westerly and are affected by the prevailing winds and swell.
Cawsand Bay faces in a south-easterly direction and was fishable in all
but a strong south-easterly wind. The substrate of these survey sites is
mainly ‘soft ground’. Most of the current commercial fishing in
Bigbury Bay and Whitsand Bay is undertaken during the spring and
summer months with fishermen using static gear, such as gill nets and
crab pots. There is limited trawling in both locations, as current fishing
bylaws restrict the size of vessels trawling inside the 6 mile limit to
15.24 m in Devon while the limit is 18.28 m or 221 kW engine power
in Cornwall.
2.2. Historical survey
Records were derived from MBA naturalist's logbooks held in the
National Marine Biological Library (NMBL) archive. The trawls were
undertaken on SS Oithona, a 25.3 m steam powered work boat, that
was capable of trawling at an estimated 1.29 ms− 1 (Kyle, 1903).
Logbooks contain a description of the otter trawl used, including a
12.2 m head rope and a 38 mm cod-end. Although there is reference
to a cod-end liner, there is no mention of size, or if it was used
consistently throughout the sampling period. Logbooks contain
information on the location (based on transits and estimated
distances from known fixed points), duration of trawls, and the
abundance and total length of (TL) species collected. Data were only
included in the analyses if both species abundance and length
information were recorded from all individuals caught. In total, this
resulted in the use of records from 53 trawls (six in Bigbury Bay, 23 in
Cawsand Bay and 24 in Whitsand Bay) with a mean duration of
46.8 min (range 30 to 60) for Bigbury Bay, 35.4 min (14 to 60) for
Cawsand Bay and 47.2 min (20 to 90) for Whitsand Bay (Table 1).
2.3. Contemporary resurvey
The contemporary resurvey was undertaken on the research vessel
MBA Sepia, a 15.4 m purpose-built, Marine and Coastguard Agency
M. McHugh et al. / Journal of Sea Research 65 (2011) 187–194
004° 15’ W
189
004° 00’ W
N
50° 20’ N
CW
WB
20m
20m
BB
1km
50° 15’ N
Fig. 1. Sampling locations of historic and contemporary surveys marked by hatched areas: WB Whitsand Bay, CW Cawsand Bay, BB Bigbury Bay.
Table 1
Details of historic and contemporary trawls at the three study sites; Bigbury Bay (BB);
Cawsand Bay (CW); Whitsand Bay (WB).
Year
Month
1913
1913
1913
1913
1913
1914
1919
1919
1920
1920
1920
1921
1921
1921
1922
2008
2008
2008
2008
2008
2008
2009
2009
2009
2009
June
July
August
September
October
April
August
September
June
July
September
September
October
December
January
April
June
August
September
October
November
January
February
March
April
Number of trawls
Mean trawl duration (range) in minutes
BB
CW
WB
BB
CW
WB
–
–
2
2
–
–
2
–
–
–
–
–
–
–
–
–
5
6
–
5
–
6
–
5
6
1
–
4
5
1
1
1
–
2
2
–
1
1
3
1
–
–
–
–
–
–
–
–
–
–
2
4
6
1
3
2
–
1
–
–
2
2
1
–
–
7
5
–
6
–
6
–
6
–
6
–
–
46 (32–60)
60 (60–60)
60
35
33 (30–35)
–
–
–
–
–
–
–
–
–
19 (15–20)
20 (20–20)
–
20 (20–20)
–
20 (20–20)
–
20 (20–20)
20 (20–20)
60
–
30 (14–49)
44 (38–60)
–
–
30
–
30 (30–30)
20 (20–20)
–
18 (15–20)
30
32 (30–35)
60
–
–
–
–
–
–
–
–
–
–
52 (33–70)
43 (20–60)
77 (60–90)
75
63 (60–70)
45 (30–60)
–
30
–
–
25 (20–30)
32 (30–35)
30
–
–
20 (20–20)
20 (20–20)
–
20 (20–20)
–
20 (20–20)
–
20 (20–20)
–
20 (20–20)
2.4. Data analysis
2.4.1. Data preparation
There was a marked discrepancy in the frequency of small fishes
between historic and contemporary surveys (Fig. 2). Although this is
potentially a consequence of increases in the number of small species
(e.g. sand goby Pomatoschistus minutus), it may also reflect differences
in selectivity of gears for smaller fish. To avoid potential confounding
effects of mesh selectivity in analyses, the conservative approach of
only including individuals greater than 15 cm standard length was
adopted. In addition to analyses based on the whole assemblage,
species were divided into three distinct subgroups: elasmobranchs,
roundfish (= teleosts excluding Pleuronectiformes) and flatfish
(= Pleuronectiformes).
2.4.2. Changes in community composition and length distributions
Species abundance data were adjusted to catch per unit effort
(CPUE, individuals per hour), log10(x + 1) transformed in order to
include rare and absent (zeroes) species with highly abundant species
on a more comprehensible graph, and differences between sites and
survey periods were calculated using 2-way Analysis of Similarities
(ANOSIM) in Primer 6 (Clarke and Gorley, 2006). Similarities of
sample composition were ordinated using two-dimensional Multidimensional Scaling (MDS) in Primer 6. Differences in abundance
between sites and survey periods were assessed using 2-way ANOVA.
To explore differences in length distributions, data were pooled from
Total individuals sampled log10 (x +1)
(MCA) certified, category 2 workboat (capable of operating up to
60 miles from safe haven). The gear used was an otter trawl with a
12 m head rope and a 12 mm (stretched) mesh size net liner, covering
a 50 mm (mesh) cod-end. The otter trawl was towed between 1.03
and 1.29 ms− 1. The area trawled for Bigbury Bay (ICES 29E6)
was contained within a box of 2.76 km2 (3°53.00′W to 3°55.97′W,
50°16.05′N to 50°14.87′N). The area trawled for Whitsand Bay (ICES
29E5) was contained within a box of 2.83 km2 (4°14.20′W to 4°15.61′W,
50°20.58′N to 50° 19.17′N). In total 69 trawls (33 in Bigbury Bay and
36 in Whitsand Bay) were undertaken with a mean duration of
19.8 min (range 15 to 20) for Bigbury Bay, and 20.0 min (range 20 to 20)
for Whitsand Bay (Table 1). All fish collected were identified to species
(Wheeler, 1978), and TL and individual mass measured. Nomenclature
adopted follows Froese and Pauly (2009).
5
4
3
2
1
0
0
10
20
30
40
50
60
70
80
90
100
110
Length (cm)
Fig. 2. Length–frequency distributions of fish caught in the historical survey (1913 to 1922;
dashed line) and contemporary resurvey (2008 to 2009; solid line).
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M. McHugh et al. / Journal of Sea Research 65 (2011) 187–194
all sites within each survey period, and derived frequencies of
individuals within 5 cm TL categories were calculated. Differences in
length-frequencies were tested using Kolmogorov–Smirov twosample tests. Analyses were conducted initially on the whole fish
assemblage, and repeated on each distinct subgroup independently.
3. Results
Analyses including all species demonstrated highly significant
differences in assemblage structure among sampling locations, and
between sampling periods (Table 2; Fig. 3). However, although spatial
differences were present between all subgroups of the assemblage,
significant differences between sampling periods were only present
within elasmobranchs and roundfishes (Table 2; Fig. 3). This suggests
that the spatial structure of the flatfish assemblage has remained
relatively constant.
Among the most notable changes were the absence of several
elasmobranch species from the contemporary surveys, including Squatina
squatina, Raja fullonica, Leucoraja naevus and Raja circularis. By contrast
Scyliorhinus canicula has increased dramatically in abundance. Only one
individual was sampled in the historic survey, whereas 160 individuals
were caught in the contemporary survey. Within the roundfishes, the
largest observed differences were the historical presence of larger
individuals (N15 cm TL) of seven species that did not occur in the
contemporary resurvey; Conger conger, Trisopterus luscus, Trisopterus
minutus, Echiichthys vipera, Trigloporus lastoviza, Taurulus bubalis and
Lophius piscatorius. There are five species that occur in the contemporary
survey, but not in the historic survey; E. encrasicolus, Clupea harengus,
Syngnathus acus, Syngnathus rostellatus and Dicentrarchus labrax. Of these
species, two are strictly seasonal (E. encrasicolus and C. harengus),
appearing primarily in winter samples (January to April) and can possibly
be excluded on the basis of low historic sampling effort during the winter
months. The other species, however, were rare in the contemporary
survey and may just be an artefact of the increased sampling frequency.
Two-way ANOVA showed a highly significant difference in overall fish
abundance (CPUE) between survey locations (F2,121 =5.634, P=0.005),
but not periods (F1,121 = 3.431, P = 0.066; Table 3). No significant
differences were found in total abundance of elasmobranchs between
locations (F2,121 =1.175, P=0.312), or periods (F1,121 =0.576, P=0.449).
After removal of S. canicula there was also no difference between locations
(F2,121 = 0.976, P = 0.380), but there was a significant decline in
abundance between sampling periods (F1,121 =18.917, Pb 0.001). In
roundfishes there was a significant difference between locations
(F2,121 = 8.444, P b 0.001), but not sampling periods (F1,121 = 2.515,
P=0.116), and in flatfishes there are no significant differences in
abundance between locations (F2,121 =0.167, P=0.847), or periods
(F1,121 =2.762, P=0.10).
Including all taxa, there was no significant change in the lengthdistribution of the fish community between the historic and contemporary surveys (median TL 550 and 375 respectively, K–S test, D = 0.25,
P = 0.497; Fig. 4a). However there was a significant decline once S.
canicula was removed (median TL 550 and 375 respectively, D = 0.45,
Table 2
Significance of differences in fish assemblage composition between sampling periods
(historic and contemporary) and between locations, determined using 2-way Analysis
of Similarities (ANOSIM).
Between periods
Between locations
Taxa
ANOSIM R
P
ANOSIM R
P
All
Flatfishes
Roundfishes
Elasmobranchs
0.283
0.063
0.160
0.529
b0.001
0.104
0.017
b0.001
0.316
0.163
0.318
0.109
b 0.001
b 0.001
b 0.001
b 0.001
P = 0.023; Fig. 4b). Exploring assemblage subgroups separately, there
was no significant differences in size within flatfishes between the
surveys (median TL 275 and 275 respectively, D = 0.13, P = 1.000;
Fig. 4c), or within roundfishes (median TL 300 and 175 respectively,
D = 0.25, P = 0.497; Fig. 4d). There was however a significant increase in
median size of elasmobranchs with S. canicula included (median TL 425
to 575, respectively, D = 0.55, P = 0.003; Fig. 4e), but when S. canicula
was excluded this reversed to a significant decline (median TL 575 and
425 respectively, D = 0.75, P b 0.001; Fig. 4f).
4. Discussion
This study provides evidence of long-term changes in a temperate
inshore fish assemblage around Plymouth. Our analysis shows a
highly significant shift in the overall species assemblage over time,
despite relative temporal consistency in the overall numbers of fish,
potentially reflecting the influence of both commercial fishing and
regional climatic changes. There is increasing theoretical and
empirical evidence that overfishing can lead directly to major changes
in fish populations (Hutchings and Reynolds, 2004), by truncating the
size structure (Genner et al., 2010b), and driving declines in
abundance (Hutchings and Baum, 2005). However, we observed no
significant change in the size frequency distributions of flatfish or
roundfishes between the historic and contemporary trawls. At our
study site the commercial species of flatfishes and roundfishes in both
trawl surveys were mostly comprised of subadult fishes, smaller than
the present day accepted minimum landing sizes in UK waters.
Plausibly the absence of larger individuals is because many species
tend to occupy areas of greater depth than at our sites (e.g. Svedäng,
2003), and/or are further offshore (Hyndes et al., 1999). Thus, our
sampling may not have captured shifts in size frequencies of these
species reported in studies of waters further offshore (e.g. Genner
et al., 2010a).
In contrast to the absence of change in the size distribution of
teleosts, we observed a highly significant decline in the size
distribution and abundance of the elasmobranch assemblage, but
only after now abundant lesser-spotted catshark S. canicula was
removed. It is possible that the change between the historic and
contemporary surveys could be partly due to variation in mesh size of
the cod end. It is unclear to whether a small mesh cod end liner was
used in all of the historic trawls, but they were used on the
contemporary trawls. This is important because a small meshed cod
end retains a greater number of small fish and can potentially have the
effect of creating a backwash out through the mouth of the trawl
giving larger, more powerful, fish a greater chance of escape, for
example see Mous et al. (2002). Another possible explanation for the
observed change in length of the elasmobranchs was due to a bias
towards recording ‘food fish’ (fish N 100 mm) as occurred in other
surveys at the time carried out by the Marine Biological Association
(Garstang and Kyle, 1903; Anon, 1912). In an effort to compensate for
any overestimation in changes of abundance, only fish greater than
150 mm were used in these analyses, thus eliminating smaller
individuals and smaller species. On balance, we feel that neither
contrasting mesh sizes nor recording bias can explain the decline in
the sizes of elasmbranchs, and instead the data suggest that large
elasmobranchs are now rare in the assemblage. This interpretation is
partly because the data suggest that the contemporary gear was able
to catch large (50 cm+) elasmobranchs, notably S. canicula, and partly
because the same pattern has been observed in offshore waters
around the UK (Walker and Hislop, 1998; Dulvy et al., 2000),
including further offshore in the western English Channel (Genner
et al., 2010a,b).
The shift in size distribution of elasmobranchs was paralleled by
changes in abundance, with all seven species of skate encountered
in the hauls declining during the last century. This has brought
about an overall reduction in the diversity of the elasmobranch
M. McHugh et al. / Journal of Sea Research 65 (2011) 187–194
(a, all fish)
191
(b, flatfish)
Stress: 0.26
(c, roundfish)
Stress: 0.21
(d, elasmobranchs)
Stress: 0.12
Stress: 0.08
Fig. 3. Multidimensional scaling (MDS) ordination plots of community similarity within the historic and contemporary trawls for (a) all species, (b) flatfish, (c) roundfish and (d) elasmobranchs.
Closer points represent trawls of more similar composition (Historic: ● Cawsand, ▲ Whitsand, ■ Bigbury; Contemporary △ Whitsand, □ Bigbury). Stress values b 0.2 provide an accurate twodimensional representation of data (Clarke and Gorley, 2006).
assemblage, and agrees with wider observations of the declines in
size and CPUE of benthic elasmobranch species in European waters
(Rijnsdorp et al., 1996; Dulvy et al., 2000; Pinnegar et al., 2002;
Clarke, 2008). Despite their continued presence in hauls, the most
prominent declines have taken place in spotted ray (Raja montagui),
thornback ray (R. clavata) and blonde ray (R. brachyura). Other
species that were rare in the historic trawls, were absent from
contemporary surveys, namely cuckoo ray (L. naevus) and shagreen
ray (L. fullonica). Notably, qualitative information obtained from
research vessel fishing charts (RV Sepia) suggests cuckoo ray was
common approximately 3 km south of the Whitsand Bay trawling
area between 1969 and 1976, information confirmed by vessel
skippers (N. Revill and F. Hutchings, pers. comm.). According to Ellis
et al. (2004) cuckoo ray are now only found in deeper waters along
the continental shelf, suggesting that declines in this species have
taken place within the last 30 years.
Importantly, the formerly abundant angel shark (S. squatina) was
absent in our contemporary survey, supporting fisheries evidence of
major declines in angel shark from the wider English Channel region
(Rogers and Ellis, 2000; ICES, 2008). The apparent extirpation of angel
shark from Plymouth waters in particular is corroborated by research
vessel logbooks (RV Sepia) that contained the last recorded catches of
angel shark in the region between 1969 and 1972, located outside the
Yealm estuary approximately halfway between Cawsand Bay and
Bigbury Bay. However, this is not the only large demersal elasmobranch now eradicated from the area. Common skate (D. batis) was
formerly “very common” in the waters around Plymouth Sound as
recent as the 1880s (Heape, 1888). That the common skate was not
recorded in the inshore trawl data collected three decades later
demonstrates the speed with which fisheries can deplete stocks of
slow-growing and long-lived species. Subsequently, no common skate
have been encountered in survey trawls in the areas adjacent to
Plymouth Sound in the past 100 years (Genner et al., 2010b, MBA
unpublished data). Similarly Ellis et al. (2004) reported no common
skate in the inshore waters in larger scale surveys of the Western
English Channel between 1967 and 2002, however they are still
encountered in offshore fishing grounds of the western approaches
(CEFAS, 2007; Griffiths et al, 2010).
Together these data provide further evidence that skates are
susceptible to capture as non-target species (Walker and Hislop,
1998; Reynolds et al., 2002) and as a group of species that are slowgrowing, late maturing with long generation times (Stevens et al.,
2000; Reynolds et al., 2002), are particularly vulnerable to
exploitation. It was notable that only one species of elasmobranch
has markedly increased in abundance, the small-spotted catshark
(S. canicula), a small elasmobranch species (max 100 cm TL,
Wheeler, 1978) with little commercial value, and high discard
survivorship (Revill et al., 2005). The marked increase in abundance
of S. canicula over the time period has also been recorded in other
surveys of the Western English Channel region (Rogers and Ellis,
2000; Genner et al., 2010b), and the North Sea (Clarke, 2008)
suggesting broad evidence for a significant population increase over
the last 100 years.
There is credible evidence that climatic variability can significantly
alter local species abundances in survey trawls through changes to
population sizes, distributions and migration phenology. However,
inference of climatic responses is best done using time series, and our
study was necessarily based on two discrete time periods, with a
significant time interval. Nevertheless, the patterns in these data
match some of those found in long-term data that have been
attributed to climatic shifts. In particular, increases were noted in
small-spotted catshark and common dragonet (Callionymus lyra),
paralleling evidence from offshore surveys (N50 m depth) in areas
adjacent to our survey sites (Genner et al., 2010b), and suggesting
some influence of long-term climate variability.
This study repeated some of the earliest quantitative surveys of
inshore fisheries in UK waters, but it is unlikely that during 1911–1922
the inshore fish assemblages were in a pristine condition. Large-scale
inshore marine trawl fisheries were operating within the southwest of
England from the mid 18th Century, and supplying the then ‘distant’
markets in Bristol, Bath and London (Robinson, 1996). Fixed gears
operating on a commercial scale are likely to have been operating
192
M. McHugh et al. / Journal of Sea Research 65 (2011) 187–194
Table 3
Mean abundance (CPUE, numbers of individuals ≥ 15 cm TL per hour) in historic and contemporary trawls at: BB Bigbury Bay, CW Cawsand Bay, WB Whitsand Bay. 95% confidence
intervals of the mean are in parentheses.
Species group
Elasmobranchs
Roundfish
Flatfish
All species
Species
Scyliorhinus canicula
Mustelus mustelus
Squatina squatina
Leucoraja fullonica
Leucoraja naevus
Raja circularis
Raja montagui
Raja clavata
Raja microocellata
Raja brachyura
All elasmobranchs
All except S. canicula
Engraulis encrasicolus
Clupea harengus
Conger conger
Syngnathus acus
Syngnathus rostellatus
Merlangius merlangus
Trisopterus luscus
Trisopterus minutus
Zeus faber
Dicentrarchus labrax
Ammodytes sp.
Echiichthys vipera
Callionymus lyra
Eutrigla gurnardus
Trigloporus lastoviza
Aspitrigla cuculus
Chelidonichthys lucerna
Taurulus bubalis
Lophius piscatorius
All roundfish
Psetta maxima
Scophthalmus rhombus
Arnoglossus laterna
Limanda limanda
Platichthys flesus
Pleuronectes platessa
Microstomus kitt
Pegusa lascaris
Solea solea
Buglossidium luteum
Microchirus variegatus
All flatfish
All fish
Historic
Small-spotted catshark
Smooth-hound
Angelshark
Shagreen ray
Cuckoo ray
Sandy ray
Spotted ray
Thornback ray
Small-eyed ray
Blonde ray
European anchovy
Atlantic herring
European conger
Greater pipefish
Nilsson's pipefish
Whiting
Pouting
Poor cod
John dory
European seabass
Sandeel
Lesser weaver
Dragonet
Grey gurnard
Streaked gurnard
Red gurnard
Tub gurnard
Longspined bullhead
Angler
Turbot
Brill
Scaldfish
Dab
flounder
European plaice
Lemon sole
Sand sole
Common sole
Solenette
Thickback sole
Contemporary
BB
CW
WB
BB
WB
0.17
0.00
0.00
0.00
0.29
0.00
2.70
7.45
0.00
0.00
10.60 (4.65)
10.43 (4.76)
0.00
0.00
0.00
0.00
0.00
0.00
0.33
0.00
1.00
0.00
0.00
0.00
7.89
36.37
0.00
3.12
0.65
0.00
0.17
49.52 (39.29)
0.00
0.98
0.00
13.98
0.00
2.34
0.00
0.48
4.43
0.00
0.00
22.21 (12.67)
82.34 (51.56)
0.00
0.00
3.07
0.00
0.00
0.00
0.69
3.86
0.09
6.09
13.80 (6.14)
13.80 (6.14)
0.00
0.00
0.00
0.00
0.00
0.16
0.78
0.00
0.85
0.00
0.00
0.05
1.34
0.54
0.20
0.00
0.81
0.82
0.00
5.58 (2.72)
0.00
0.34
0.18
3.40
0.29
11.73
0.07
0.99
3.23
0.00
0.00
20.24 (6.06)
39.62 (10.69)
0.00
0.00
1.61
0.50
0.00
0.13
0.71
1.70
0.86
4.72
10.22 (4.34)
10.22 (4.34)
0.00
0.00
0.11
0.00
0.00
1.08
0.00
0.07
0.92
0.00
0.58
0.00
2.27
2.10
0.00
0.00
0.83
0.00
0.28
8.24 (4.00)
2.47
0.61
0.20
3.47
0.13
4.59
0.00
3.57
2.14
0.46
0.00
17.64 (7.05)
36.09 (12.48)
9.82
0.00
0.00
0.00
0.00
0.00
0.18
0.09
0.18
0.00
10.27 (5.11)
0.45 (0.45)
0.00
0.18
0.00
0.09
0.00
1.18
0.00
0.00
0.27
0.00
0.09
0.00
42.03
11.73
0.00
0.36
5.58
0.00
0.00
61.52 (17.45)
2.75
0.83
2.00
0.75
1.33
11.83
0.00
11.58
1.92
0.42
0.00
33.42 (7.21)
95.06 (17.66)
4.33
0.08
0.00
0.00
0.00
0.00
0.25
0.08
0.50
0.58
5.83 (2.41)
1.50 (0.79)
0.17
0.00
0.00
0.08
0.17
0.00
0.00
0.00
0.25
0.17
21.33
0.00
2.92
0.00
0.00
0.00
1.00
0.00
0.00
26.08 (13.12)
0.18
0.27
1.91
6.70
0.18
9.33
0.00
1.55
3.06
0.00
0.09
23.27 (7.35)
65.33 (15.76)
for even longer. Given over 250 years of inshore fisheries it is thus
not possible to determine accurately how the assemblage would
have been structured prior to the initiation of fishing. Nevertheless,
evidence from the North Sea, based on macroecological predictions,
suggests that larger species were once much more abundant on the
European continental shelf (Jennings and Blanchard, 2004). Taken
together, this evidence suggests that the data from the historic 1913–
1922 study should not be used as a baseline on which to base recovery
to a pristine state for protected areas, but rather as a marker of
improving status.
In summary, our study provides further evidence from new sites for
fisheries-induced declines in several of the larger, slower growing, late
maturing elasmobranch species in waters of the European continental
shelf. By contrast we found no evidence for significant changes in the
abundance, size structure and diversity of teleost flatfish species.
Diverse assemblages of species are important for stable ecosystems to
function correctly and they need to be retained, even for common and
widespread species (Gaston and Fuller, 2007). Failing to prevent
collapse of a population could have negative consequences for the
local ecosystem (Hutchings and Reynolds, 2004). With more emphasis
being placed on the value of historic data regarding the condition of our
seas (Holm, 2002; Sáenz-Arroyo et al., 2006), it is perhaps timely to link
conservation and management planning with historical information.
Moreover, as these surveys were carried out in an area that is not
covered by government surveys, they provide an insight into long-term
change within a potentially important habitat within North Atlantic
coastal waters.
Acknowledgements
We thank the past and present MBA scientists and captains and
crew of research vessels who contributed to data collection. Work
was supported by the UK Natural Environment Research Council
(NERC) through Themes 6 and 10 of the Oceans 2025 Strategic
Research Programme, UK Department for Environment, Food and
Rural Affairs (Defra), and a NERC-Defra Sustainable Marine Bioresources standard grant award NE/F001878/1. Additional funding
was provided by the Fishmongers Company. MJG was supported by a
Great Western Research Fellowship and DWS by an MBA Senior
Research Fellowship.
M. McHugh et al. / Journal of Sea Research 65 (2011) 187–194
60
(a, all fish)
Percent frequency
(b, all fish excluding S. canicula)
Historic
Contemporary
40
60
40
20
20
0
0
(c, flatfish)
(d, roundfish)
40
80
30
60
20
40
10
20
0
0
50
(e, elasmobranchs)
20
40
16
30
12
20
8
10
4
0
193
15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100105110
0
(f, elasmobranchs excluding S. canicula)
15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100105110
Total length (cm)
Fig. 4. Frequency distributions of fish (≥ 15 cm) in historic and contemporary trawls expressed as percentage of all individuals sampled: (a) All fish, (b) all fish excluding Scyliorhinus
canicula, (c) flatfish, (d) roundfish, (e) elasmobranchs, and (f) elasmobranchs excluding Scyliorhinus canicula.
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