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Feeding ecology of the deep-sea lanternshark Etmopterus pusillus (Elasmobranchii: Etmopteridae) in the northeast Atlantic

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This study provides the first description of the feeding ecology of the smooth lanternshark Etmopterus pusillus based on stomach contents of specimens caught as bycatch in the Algarve (southern Portugal) with bottom trawling and bottom longline. The diet of E. pusillus consists mainly of fish (dry weight (% W)=87.1%; frequency of occurrence (%FO)=28.6%; number (%N)=30.3%), crustaceans (%W=7.7%; %FO=36.7%; %N=3.4%) and cephalopods (%W=4.7%; %FO=11.3%; %N=11.1%). The diet did not vary between sexes. Ontogenic changes were detected: crustaceans decreased in importance as the sharks increased in size and fish became dominant in the diet of adults. Combining two fishing methods provided broad information on the diet of E. pusillus, as bottom trawling caught smaller specimens and longlines caught larger individuals. E. pusillus feeds mainly on non-commercial species, and therefore does not compete directly with commercial fisheries. Finally, E. pusillus feeds in various parts of the water column and thus it can access a wide range of prey; however, this also means that it can be caught by both gears, making it more vulnerable in terms of conservation.
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Feeding ecology of the deep-sea lanternshark
Etmopterus pusillus (Elasmobranchii: Etmopteridae)
in the northeast Atlantic
JOSÉ C. XAVIER
1
, CÁTIA VIEIRA
2
, CARLOS ASSIS
3
, YVES CHEREL
4
, SIMEON HILL
5
,
ESMERALDA COSTA
2
, TERESA C. BORGES
2
and RUI COELHO
2
1
Institute of Marine Research (IMAR-CMA), Department of Life Sciences, University of Coimbra, 3004-517 Coimbra,
Portugal.
2
Centre of Marine Sciences (CCMAR), University of Algarve. Campus de Gambelas, 8000-139 Faro, Portugal.
E-mail: rpcoelho@ualg.pt
3
Department of Animal Biology and Institute of Oceanography, Faculty of Sciences, University of Lisbon.
Campo Grande, 1749-016 Lisbon, Portugal.
4
Centre d´Etudes Biologiques de Chizé, UPR 1934 du Centre National de la Recherche Scientifique, BP 14,
79360 Villiers-en-Bois, France.
5
British Antarctic Survey, High Cross, Madingley Road, CB3 0ET, Cambridge, UK.
SUMMARY: This study provides the first description of the feeding ecology of the smooth lanternshark Etmopterus pu-
sillus based on stomach contents of specimens caught as bycatch in the Algarve (southern Portugal) with bottom trawling
and bottom longline. The diet of E. pusillus consists mainly of fish (dry weight (% W)=87.1%; frequency of occurrence
(%FO)=28.6%; number (%N)=30.3%), crustaceans (%W=7.7%; %FO=36.7%; %N=3.4%) and cephalopods (%W=4.7%;
%FO=11.3%; %N=11.1%). The diet did not vary between sexes. Ontogenic changes were detected: crustaceans decreased
in importance as the sharks increased in size and fish became dominant in the diet of adults. Combining two fishing methods
provided broad information on the diet of E. pusillus, as bottom trawling caught smaller specimens and longlines caught
larger individuals. E. pusillus feeds mainly on non-commercial species, and therefore does not compete directly with com-
mercial fisheries. Finally, E. pusillus feeds in various parts of the water column and thus it can access a wide range of prey;
however, this also means that it can be caught by both gears, making it more vulnerable in terms of conservation.
Keywords: deep-sea fisheries, elasmobranch, Etmopterus pusillus, feeding ecology, lanternshark.
RESUMEN: Ecología alimentaria del tiburón tollo lucero liso EtmoptErus pusillus (Elasmobranchii: Etmopte-
ridae) en el Atlántico Nordeste. Se proporciona la primera descripción de la ecología alimentaria del tiburón tollo lu-Se proporciona la primera descripción de la ecología alimentaria del tiburón tollo lu-
cero liso Etmopterus pusillus mediante el análisis de contenidos estomacales de individuos capturados accidentalmente en el
Algarve (sur de Portugal) mediante arrastre y palangre de fondo. La dieta de E. pusillus consiste mayoritariamente en peces
(%W=87.1%; %FO=28.6%; %N=30.3%), crustáceos (%W=7.7%; %FO=36.7%; %N=53.4%) y cefalópodos (%W=4.7%;
%FO=11.3%; %N=11.1%; % W=peso seco, %FO=Frecuencia de aparición, %N=Número). No se observaron diferencias
entre sexos en su dieta, pero cambios ontogénicos, con los crustáceos disminuyendo en importancia a medida que el
tiburón alcanza tallas mayores, y los peces dominando la dieta de los adultos. Ambos tipos de pesquería proporcionaron
información adecuada sobre la dieta de E. pusillus, con el arrastre capturando tallas menores, y el palangre capturando ani-
males mayores. Al alimentarse mayoritariamente de especies sin interés comercial, este tiburón no compite activamente con
ninguna pesquería para obtener recursos alimentarios. Finalmente, E. pusillus se alimenta en varios niveles de la columna
del agua, lo que le aporta mayor diversidad de presas, aunque también significa que puede ser capturado por ambos artes de
pesca, convirtiéndolo en más vulnerable en términos de conservación.
Palabras clave: pesquerías demersales, elasmobranquios, Etmopterus pusillus, ecología alimentaria, tiburón tollo lucero
liso.
Scientia Marina 76(2)
June 2012, 301-310, Barcelona (Spain)
ISSN: 0214-8358
doi: 10.3989/scimar.03540.07B
302 J.C. XAVIER et al.
SCI. MAR., 76(2), June 2012, 301-310. ISSN 0214-8358 doi: 10.3989/scimar.03540.07B
INTRODUCTION
Many shark species play a key role as top preda-
tors in marine ecosystems (Cortés and Gruber 1990,
Cortés 1999), preying on organisms throughout the
food web or acting as scavengers (Sims and Quayle
1998, Stevens et al. 2000, Hantz 2003). Furthermore,
they exploit a wide range of habitats, from epipelagic
to deep-sea benthic environments, where they play an
important role in the regulation of lower trophic levels
(Cortés 1999, Stevens et al. 2000).
There is growing concern about potential top-down
cascade effects that could be caused by the overfish-
ing of sharks (Pauly et al. 1998, Lehodey and Maury
2003). Most sharks have K-selected life history strate-
gies (Stevens et al. 2000), and as such they are highly
susceptible to rapid overexploitation (Moore and Mace
1999). Studies are therefore necessary on the role
played by poorly understood shark species in marine
ecosystems, including studies on their feeding ecology.
Determining the food and feeding ecology of sharks
is of paramount importance in order to clarify the re-
lationships between sharks, prey availability and fish-
eries. Modelling relationships with fisheries requires
detailed information on the biology of the sharks and
their prey. Furthermore, it is important to evaluate the
diet of sharks according to sex because juveniles, adult
males and adult females may aggregate in separate
groups (Springer 1967, Myrberg and Gruber 1974,
Sims 2005).
Portugal is the third greatest shark fishing nation in
Europe and has the second largest fishing fleet (FAO
2006, Gibson et al. 2008). Around 60 shark species oc-
cur in the Algarve region (southern Portugal, northeast
Atlantic), and several deep water species, including
Etmopterus spp., are commonly caught as bycatch and
discarded (Monteiro et al. 2001, Coelho et al. 2005).
The smooth lanternshark Etmopterus pusillus
(Lowe, 1839) is a deep water lanternshark with a
global distribution that is caught in large quantities in
some areas, but is discarded as it has low or no com-
mercial value (Coelho et al. 2003, Coelho and Erzini
2007). It is distributed on the continental shelves and
upper slopes at depths between about 300 and 1000 m
(Whitehead et al. 1986). As it is always discarded, E.
pusillus catches are not recorded, and the species is not
listed in the fisheries statistics of Portugal (Coelho and
Erzini 2005). Consequently, it is very difficult to gather
information on the status of this species, and informa-
tion on its biology has only recently become available
(Coelho and Erzini, 2005, 2007, 2008a, b). Moreover,
there is no detailed information on the feeding ecology
of E. pusillus in any part of the world.
In southern Portugal, E. pusillus is caught both
by bottom trawlers targeting crustaceans and bottom
longliners targeting bony fish (Monteiro et al. 2001,
Coelho et al. 2005). Trawling usually catches a broader
range of species and size groups than passive gears like
longlines because the latter relies on attraction to bait
(Cotton et al. 2005) and excludes very small fish which
cannot ingest the hooks (FAO 2006). The use of both
bottom trawls and bottom longlines as sampling gears
could provide insight into ontogenic shifts in feeding
habits as a wide range of shark sizes can be sampled.
The main goal of the present study was to describe
the feeding ecology of E. pusillus in the northeastern
Atlantic waters (Algarve, Portugal) using two differ-
ent fishing methods. The questions addressed were: 1)
What is the overall diet of E. pusillus? 2) Are there sex
related differences in the diet? 3) Are there ontogenic
differences in the diet? 4) Are there any differences
between the diets of the specimens sampled by the two
different fishing gears? and, finally, 5) What do these
results imply for shark conservation and management?
MATERIALS AND METHODS
Sample collection
Specimens of E. pusillus were recovered from bot-
tom longlines (targeting wreckfish (Polyprion america-
nus), European conger (Conger conger), redfish (Heli-
colenus dactylopterus) and emperors (Beryx spp.)) and
bottom trawls (targeting high-value crustaceans like
deepwater rose shrimp (Parapenaeus longirostris) and
Norway lobster (Nephrops norvegicus)). Both gears
were employed off the coast at depths between 200 and
700 m (Borges et al. 2001, Xavier et al. 2010) (Fig. 1).
Trawling took place from February to December
1998, February-September 1999, February-September
2000 and February-October 2003. Longline sampling
was carried out between May 2003 and March 2004.
At least 30 individuals were recovered each month dur-
ing these periods. The specimens were cooled immedi-
ately after capture and frozen at –18°C upon arrival at
the laboratory.
Laboratory methodology
In the laboratory, all specimens were measured for
total length, weighed and sexed. The maturity stage
of each specimen was determined with a macroscopic
examination of the gonads and claspers. The stomachs
were removed and kept in plastic containers, labeled
and immersed in 10% formalin solution buffered with
sodium tetraborate for 48 h (Sá et al. 2006). They were
subsequently stored in 70% ethanol solution.
All components were removed from the stomachs,
weighed and sorted into categories (cephalopods,
crustaceans and fish) in a tray following Xavier et al.
(2010). Each item was individually analysed. In order
to avoid digestion biases, prey items were identified
mainly based on fresh hard parts (e.g. fish otoliths,
cephalopod beaks, crustacean carapaces/parts) and
flesh, to the lowest taxonomic level possible. The taxa
identified to a low taxonomic level were displayed in
figures and tables in order to provide as much detail as
FEEDING ECOLOGY OF THE SMOOTH LANTERNSHARK 303
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possible (i.e. the authors preferred to mention the taxa
identified as Sepiolidae and Ommastrephidae rather
than including all these taxa in a broader taxa, in this
example, the class Cephalopoda, as this illustrates some
prey selection by the studied sharks). Chub mackerel
Scomber japonicus was used as bait for the longliners,
and therefore any food item identified as bait (usually
clearly cut in half, with evidence of hook damage and
in extremely good condition) was excluded from the
analysis.
The samples were placed in an oven at 60°C for
at least 48 h (depending on the size and composition
of the prey) until a constant dry weight was obtained.
Samples were weighed on an analytical balance precise
to 0.0001 g.
Data analysis
The quantity and quality of the diet was described
using the following metrics: by number (%N; number
of individuals of a certain species divided by the total
number of individuals analysed ×100), by frequency of
occurrence (%FO; number of stomach samples with a
certain species present divided by the total number of
individuals analysed ×100), and by dry weight (%W;
estimated mass of all individuals of a certain species
divided by the total estimated mass for all individuals
analysed ×100) following Hureau (1970). The total
weight of each prey was also estimated based on the
reconstructed mass (%MR) of the prey by taxonomic
group using allometric equations (see below). Cumu-
lative richness curves were constructed to determine
whether the number of specimens with food in their
stomachs was sufficient to characterize the diet of E.
pusillus. The number of samples was sufficient to de-
scribe the diet (using a model to replicate 100 cumu-
lative curves by choosing the specimen to be studied
first randomly; see Xavier et al. 2005). For the trawling
gear, the mean number of samples needed in order to
determine the maximum number of prey was 198±0.4
(range: 113-213; 295 stomachs containing food were
analysed in this study). For the longline gear, the mean
number of samples needed was 46±0.2 (range 18-55;
148 stomachs containing food were analysed). Com-
bining these two gears, the mean number of specimens
needed to characterize the diet was well below the
number of specimens containing food: 122±1.7 sam-
ples (range: 18-213; a total of 443 stomachs with food
were analysed).
When the degree of digestion allowed it, the total
length of the prey was determined. Fish species were
identified and their reconstructed mass and length were
estimated based on otoliths following Assis (2000).
Beaks of cephalopods were identified using reference
collections and the reconstructed mass and length of
cephalopods were estimated using the following equa-
tions (Clarke 1986, Xavier et al. 2010, Xavier, Borges
and Sendão, unpublished data):
Illex coindetii:
ML=31.80367 × LRL + 20.42327
(r
2
=0.88, n=204; ML=56-278 mm);
Fig. 1. – Location of the longline (black circles) and trawl (grey circles) sets that provided Etmopterus pusillus samples for this study.
304 J.C. XAVIER et al.
SCI. MAR., 76(2), June 2012, 301-310. ISSN 0214-8358 doi: 10.3989/scimar.03540.07B
LN M (g) = 2.167534 × LN (LRL) 1.570273
(r
2
=0.80, n=203 (4-559 g);
Todaropsis eblanae:
ML= 22.59283 × LRL + 5.673228
( r
2
=0.79, n=89; ML=55-147 mm);
LN M (g)=2.506635 × LN (LRL) 0.777538
(r
2
=0.85, n=89 (14-205 g))
where ML is the mantle length, M the estimated mass
and LRL is the rostral length of the lower beak.
The prey items were categorized according to their
ecological group (GE; categories used: demersal, mes-
opelagic, pelagic and benthic) following Cortés (1997).
To assess the importance of different prey in the diet,
and facilitate comparisons between different samples
or studies, the following combined indexes were used:
the index of relative importance (IRI; IRI=(%N+ %W)
× %FO; %IRI=IRI of a given prey divided by the total
values of IRI for all prey x 100) and food coefficient
(Q; Q=%N×%W, with Q values >200 classified as
“preferential prey”, 20 Q200 as “secondary prey”
and Q<20 as “occasional prey”) (Hureau 1970).
In order to analyse the quantitative variations in the
diet with the predator’s feeding activity, the proportion
of empty stomachs (CV; CV=total number of empty
stomachs divided by the total number of stomachs ana-
lysed x 100) was calculated following Hureau (1970).
In addition, the diversity of prey species consumed by
this predator was calculated with the Shannon-Wiener
index (Shannon and Weaver 1949). The trophic level
and the ontogeny variation were calculated following
Cortés (1999).
The similarities of the diet of E. pusillus between
length classes and sexes were evaluated based on the
abundance of prey and using the Bray-Curtis similar-
ity coefficient in the “PRIMER 6” software (Clarke
and Warwick, 2001). The resulting array of similarity
values was plotted using non-metric multidimensional
scaling (MDS). The square root transformed numeri-
cal abundance of each prey item (Clarke and War-
wick 2001) was assigned to major taxonomic groups
(Myctophidae, Gadiformes, other Teleosts, Natantia,
other Crustaceans, Ommastrephidae, Sepiolidae,
other cephalopods) and used to calculate the similar-
ity matrix. Statistical inference was carried out using
the ANOSIM (Analysis of Similarities) procedure
(Clarke and Warwick 2001) available in the “PRIMER
6” software. The groups of size classes with different
diets were individually assessed and compared for the
importance of different types of prey in the diet using
the index of relative importance (%IRI), the Shannon-
Wiener diversity index and the trophic level (Cortés
1999). Finally, differences between sexes and between
the two fishing methods were also considered. The
MDS analyses on the relationship between sexes, size
classes and their diet were not conducted due to the
limited number of individuals.
All values given in the results are stated as mean ±
standard error unless otherwise stated.
RESULTS
General description of the diet
A total of 600 E. pusillus specimens were analysed,
comprising 264 females and 336 males, of which
26.1% had empty stomachs (number of specimens with
Table 1. – Number of male and female Etmopterus pusillus caught
by longline and trawl gears, categorized by stomach status.
Longline Trawl
Empty Not Empty Empty Not Empty Total
Females 77 62 9 116 264
Males 62 86 9 179 336
Total 139 148 18 295 600
Fig. 2. Length frequency distribution of Etmopterus pusillus spec-
imens (with food or empty), caught by trawling (above), longlines
(middle) and the two gears combined (bottom).
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empty stomachs=157; total length of specimens with
empty stomachs =12.0-48.5 cm; 37.7±0.5 cm; Table
1; Fig. 2). Females with food in their stomachs had a
similar range of total lengths (14.3-50.2 cm; 31.5±0.6
cm) as males (14.8-45.5 cm; 31.3±0.4 cm) (t-test=0.32;
p=0.74). The mean number of prey per stomach was
1.7±0.01 items.
A total of 459 prey items were analysed corre-
sponding to 26 taxa (Tables 2, 3 and 4). E. pusillus fed
mostly on mesopelagic and demersal prey. The only
prey species considered to be benthic (the crustacean
Plesionika sp.) made a reduced contribution to the diet
(Table 2). Fish were the most important component
in the diet according to dry weight (87.1%), and the
second according to number (30.3%) and frequency of
occurrence (28.6%) (Table 2). The blue whiting Mi-
cromesistius poutassou was the most important iden-
tifiable species according to various indices, including
dry weight (21.2%), frequency of occurrence (4.7%)
and number (5.0%) (Table 2). This species was also
classified as the only secondary prey, whereas all the
other taxa were classified as occasional. Fish were also
the main taxon in the diet according to reconstructed
mass (76%). The apparent importance of cephalopods
indicated by the %MR was five times that indicated by
the dry weight (Table 2). The trophic diversity was 1.8,
and the trophic level was 4.3.
Sex related differences
There were no significant differences in the diet
of male and female E. pusillus. The MDS plot did not
show any evidence of differences (ANOSIM statistic,
R=0.007, p=0.208). The trophic diversity was similar
for the two sexes (females=1.7, males=1.8).
Ontogenic differences
Four different size groups (TL) with distinct diets
were identified: 25 cm; 26-30 cm; 31-35 cm; and >35
cm. There were significant differences in the diet com-
position between the length classes (ANOSIM statistic,
R=0.075, p<0.01). The diet of the smallest individuals
(25 cm) was almost exclusively based on crustaceans
(%IRI=78.8%), cephalopods had an %IRI of 11.2%
and fish an %IRI of 5.5% (Fig. 3). As E. pusillus in-
creased in size, crustaceans gradually lost importance,
while fish showed the opposite trend. Cephalopods
were relatively unimportant in the diet of these sharks
throughout their ontogenic development (Fig. 3). The
same pattern was apparent for each gear type, although
there were some differences. The diet of E. pusillus
caught with bottom trawling was dominated by crus-
taceans in smaller individuals (25 cm TL) and teleost
fish in larger ones (>35 cm TL; Fig. 4). In E. pusillus
Table 2. List of identified prey categories in the diet of Etmopterus pusillus (number of individuals with food in their stomachs=443)
combining data from both trawl and longline gears. GE: ecological group (D: demersal, M: mesopelagic, P: pelagic, B: benthic, Na: not
attributable); n: number of prey; %FO: frequency of occurrence; %N: percentage in number; %MR: percentage by reconstructed mass %W:
percentage by dry weight (estimated mass within each component is in parentheses); %IRI: index of relative importance; Q: food coefficient;
and prey classification.
Prey Items GE n %FO %N %MR %W %IRI Q Classification
CEPHALOPODA 11.3 11.1 24.5 4.7 10.34
Enoploteuthidae D 3 0.7 0.7 (11.0) 0.14 7.2 Occasional
Histioteuthis corona M 1 0.2 0.2 3.3 (6.5) 0.03 1.4 Occasional
Illex coindetii M 1 0.2 0.2 8.1 (5.0) 0.02 1.1 Occasional
Onychoteuthis banksii M 1 0.2 0.2 0.1 (0.5) <0.01 0.1 Occasional
Sepietta oweniana D 1 0.2 0.2 0.4 (10.2) 0.04 2.2 Occasional
Sepiolidae M/D 2 0.5 0.4 (0.4) 0.01 0.2 Occasional
Todarodes sagittatus M 3 0.7 0.7 12.0 (2.1) 0.03 1.4 Occasional
Todaropsis eblanae D 2 0.5 0.4 0.8 (0.3) 0.01 0.1 Occasional
Cephalopods (unidentified) Na 37 8.1 8.1 (63.9) 10.07 515.4 Occasional
Occasional
CRUSTACEA 36.7 53.4 7.7 51.95 Occasional
Decapoda (unidentified) Na 2 0.5 0.4 (5.8) 0.05 2.6 Occasional
Isopoda Na 1 0.2 0.2 (<0.1) <0.01 <0.1 Occasional
Natantia Na 13 1.6 2.8 (2.8) 0.15 7.9 Occasional
Pasiphaea sp. P 3 0.5 0.7 (2.9) 0.03 1.9 Occasional
Pasiphaea sivado P 7 1.6 1.5 (33.5) 0.95 51.0 Occasional
Plesionika sp. B 1 0.2 0.2 (1.1) 0.01 0.3 Occasional
Polybius henslowi M 2 0.5 0.4 (8.4) 0.07 3.7 Occasional
Crustaceans (unidentified) Na 216 31.8 47.1 (45.5) 50.70 2139.0 Occasional
Occasional
FISH 28.6 30.3 76.0 87.1 27.89 Occasional
Benthodesmus elongatus 1 0.2 0.2 15.4 (2.7) 0.01 0.6 Occasional
Ceratoscopelus sp. M 1 0.2 0.2 (<0.1) <0.01 <0.1 Occasional
Gadiculus argenteus D 6 1.4 1.3 1.1 (8.1) 0.22 10.5 Occasional
Gonostoma sp. M/D 1 0.2 0.2 (8.6) 0.03 1.9 Occasional
Micromesistius poutassou M 23 4.7 5.0 40.5 (21.2) 2.14 106.4 Secondary
Myctophidae P 6 1.4 1.3 (2.7) 0.09 3.6 Occasional
Myctophum punctatum M 5 1.1 1.1 19.1 (1.9) 0.06 2.0 Occasional
Teleostei (unidentified) Na 96 19.4 20.9 (54.9) 25.33 1147.8
NOT IDENTIFIED Na 24 5.41 5.2 0.5 9.82 522.9
306 J.C. XAVIER et al.
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caught with bottom longlines and in the size range 26-
30 cm TL (no individuals 25 cm TL were caught),
the diet was dominated by Natantia, and the diet of the
largest specimens (>35 cm TL; Fig. 5) was dominated
by teleost and gadiform fish. Overall, Natantia and
gadiform fish were considerably more important in the
longline than the trawl samples (Figs. 4 and 5).
The diet diversity was similar for all size classes
(H’=1.2 for the 25 cm class, H’=1.5 for the 26-30 cm
class, H’=1.3 for the 31-35 cm class and H’=1.4 for the
>35 cm class).
Diet of E. pusillus according to fishing gear
A total of 313 (52.2%) of the 600 individuals ana-
lysed were caught by trawl gear and 287 (47.8%) were
caught by longlines (Table 1). The two fishing gears
sampled different parts of the E. pusillus size distribu-
tion. Trawls caught smaller individuals (TL=28.5±0.4
cm; range: 12.0-48.2 cm), and longlines caught sig-
nificantly larger individuals (TL=37.9±0.3 cm; range:
25.3-50. 2 cm) (two-sample Wilcoxon rank sum test,
W=77839, p <0.01; Fig. 2).
Longline samples had a significantly higher fre-
quency of empty stomachs (48.4%) than trawl samples
(5.7%) (χ
2
1
=141.6, p<0.05) and a higher total length
of specimens with empty stomachs (TL of longline
individuals with empty stomachs=38.4±0.4 cm; range:
25.3-48.5cm; TL of trawl individuals with empty stom-
achs=32.4±2.5 cm; range: 12.0-48.2 cm; t-test=2.43;
p<0.05). Although the diets of similar sized specimens
caught using the two different gear types were alike
(Figs. 4 and 5), between-gear differences were found
in the frequency of occurrence of the main taxonomic
groups o (χ
2
1
=15.4, p<0.05) and in the abundance of
prey (ANOSIM: R=0.1, p=0.03) (Tables 3 and 4).
Diet of smaller specimens of E. pusillus caught by
bottom trawling
In specimens caught with trawling, fish were the
most important diet component according to the dry
weight (87.2%) and the second most important accord-
ing to frequency of occurrence (30.6%) and number
(26.1%). According to the %MR, fish were also consid-
ered the main prey as they represented 66.0%, followed
by cephalopods, representing 34% (Table 3). The aver-
age number of prey was 1.8±0.08 items per stomach.
The most important prey, amongst those identified to
species level, was Pasiphaea sivado (%IRI=0.42) fol-
lowed by M. poutassou (0.34%). P. sivado was catego-
rized as secondary prey, and all other prey were cat-
egorized as occasional (Table 3). The trophic diversity
was 1.75 and the trophic level was 4.3.
Diet of larger E. pusillus caught by bottom
longlines
The longline gear caught larger specimens than
bottom trawling, and no individuals <25 cm TL were
caught using longlines. Fish dominated the diet accord-
ing to dry weight (87.0%), frequency of occurrence
Fig. 3. Index of relative importance (%IRI) of prey items in re-
lation to the size classes Etmopterus pusillus. Data from the two
fishing gears combined. Cephalopoda includes all unidentified
cephalopods except for those from the Ommastrephidae and Se-
piolidade families. Crustacea includes all unidentified crustaceans
except for Natantia. (Number of specimens with TL25 cm=96;
26-30 cm=101; 31-35 cm=89; and >35 cm=157).
Fig. 4. Index of relative importance (%IRI) of prey items in rela-
tion to the size classes Etmopterus pusillus. Data from trawl gear
only. Cephalopoda includes all unidentified cephalopods except for
those from the Ommastrephidae and Sepiolidade families. Crustacea
includes all unidentified crustaceans except for Natantia. (Number
of specimens with TL25 cm=96; 26-30 cm=94; 31-35 cm=56; and
>35 cm=49).
Fig. 5. Index of relative importance (%IRI) of prey items in re-
lation to the size classes Etmopterus pusillus. Data from longline
gear only. Crustacea includes all unidentified crustaceans except for
Natantia. (Number of specimens with TL25 cm=0; 26-30 cm=7;
31-35 cm=33; and >35 cm=108).
FEEDING ECOLOGY OF THE SMOOTH LANTERNSHARK 307
SCI. MAR., 76(2), June 2012, 301-310. ISSN 0214-8358 doi: 10.3989/scimar.03540.07B
(23.7%) and number (50.0%). Crustaceans were the
second most important group according to dry weight
(12.5%), frequency of occurrence (17.6%) and number
(39.2%) (Table 4). Fish were also considered the main
prey according to %MR (Table 4). The mean number of
prey was 1.3±0.09 items per stomach. The most impor-
tant prey identified to species level was M. poutassou
(%IRI=29.66; categorized as preferential prey), while
P. sivado was the second most important (%IRI=4.21;
categorized as secondary prey) (Table 4). The trophic
diversity was 1.84, and the trophic level was 4.3.
DISCUSSION
The diet of E. pusillus in the northeast Atlantic
To our knowledge, this is the first study focusing in
detail on the diet of E. pusillus from anywhere in the
world. Despite the high level of unidentified fish and
crustaceans that formed the bulk of the diet, our study
was able to make a valuable contribution to the knowl-
edge on the feeding ecology of this poorly known shark.
In the northeast Atlantic, particularly along the Algarve
coast, the diet of this shark is based primarily on mesope-
lagic and demersal crustaceans, fish and cephalopods,
including vertically migrating species (e.g. Pasiphaea
spp.), species with a mesopelagic distribution (e.g. Mi-
cromesistius poutassou) and exclusively benthic species
(Plesionika sp.). This latter species, the only benthic spe-
cies identified in the diet of E. pusillus, was unimportant
in the diet of the laternshark; however, it is consumed
by a large number of sympatric species in the study re-
gion, including the sharks Etmopterus spinax and Galeus
melastomus (Saldanha et al. 1995, Santos and Borges
2001, Cabral and Murta 2002, Pais 2002), which shows
that a wide range of sharks can also exploit benthic prey.
Pelagic organisms represent an important food
source for many demersal communities (Blaber and
Bulman 1987, Mauchline and Gordon 1991, Yama-
mura and Inada 2001). In our study, E. pusillus fed on
Table 3. List of identified prey categories in the diet of Etmopterus pusillus caught by trawling (number of individuals with food in their
stomachs=295). GE: ecological group (D: demersal, M: mesopelagic, P: pelagic, B: benthic, Na: not attributable); n: number of prey; %FO:
frequency of occurrence; %N: percentage in number; %MR: percentage by reconstructed mass %W: percentage by dry weight (estimated
mass within each component is in parentheses); %IRI: index of relative importance; Q: food coefficient; and prey classification.
Prey Items n %FO %N¯ %MR %W %IRI Q Classification
CEPHALOPODA 16.3 12.8 34.0 6.2 10,66
Enoploteuthidae 3 1.0 0.8 (11.5) 0.15 8.7 Occasional
Histioteuthis corona 1 0.3 0.3 4.5 (6.8) 0.03 1.7 Occasional
Illex coindetii 1 0.3 0.3 11.2 (5.2) 0.02 1.3 Occasional
Sepietta oweniana 1 0.3 0.3 0.5 (10.7) 0.04 2.7 Occasional
Cephalopods(unidentified) 35 11.6 9.1 (65.8) 10.41 580.8
CRUSTACEA 46.6 56.4 6.2 59.36
Pasiphaea sivado 4 1.4 1.0 (27.5) 0.42 25.2 Secondary
Crustaceans (unidentified) 195 41.5 50.9 (72.5) 58.94 3246.5
FISH 30.6 26.1 66.0 87.2 22.04
Gadiculus argenteus 4 1.4 1.0 1.1 (11.4) 0.19 10.8 Occasional
Gonostoma sp. 1 0.3 0.3 (12.6) 0.05 3.0 Occasional
Micromesistius poutassou 7 2.4 1.8 18.0 (11.0) 0.34 18.0 Occasional
Teleostei (unidentified) 75 22.1 19.6 (65.0) 21.46 1150.9
NOT IDENTIFIED 18 6.1 4.7 0.4 7.94 470.0
Table 4. – List of identified prey categories in the diet of Etmopterus pusillus caught by longlines (number of individuals with food in their
stomachs=148). GE: ecological group (D: demersal, M: mesopelagic, P: pelagic, B: benthic, Na: not attributable); n: number of prey; %FO:
frequency of occurrence; %N: percentage in number; %MR: percentage by reconstructed mass %W: percentage by dry weight (estimated
mass within each component is in parentheses); %IRI: index of relative importance; Q: food coefficient; and prey classification.
Prey Items n %FO %N %MR %W %IRI Q Classification
CEPHALOPODA 1.4 2.7 0.2 4.75
Cephalopods (unidentified) 2 1.4 2.7 (100.0) 4.75 270.3
CRUSTACEA 17.6 39.2 12.5 24.90
Decapoda (unidentified) 1 0.7 1.4 (11.9) 0.30 15.5 Occasional
Pasiphaea sivado 3 2.0 4.1 (49.1) 3.57 192.4 Secondary
Polibius henslowi 1 0.7 1.4 (20.5) 0.49 26.8 Occasional
Crustacean (unidentified) 21 12.8 28.4 (18.6) 20.54 511.3
FISH 23.7 50.0 87.0 55.36
Micromesistius poutassou 16 9.5 21.6 100.0 (56.7) 25.11 1210.4 Preferential
Teleostei (unidentified) 19 12.8 25.7 (43.3) 30.07 1099.0
NOT IDENTIFIED 6 4.1 8.1 0.3 14.99 810.8
308 J.C. XAVIER et al.
SCI. MAR., 76(2), June 2012, 301-310. ISSN 0214-8358 doi: 10.3989/scimar.03540.07B
pelagic prey such as Pasiphaea sivado, which is very
common to 300 m depth in the pelagic zone although
its distribution extends from 10 m to 600 m (Alvarez
1968). It is also possible that E. pusillus performs verti-
cal feeding migrations, which is a common behaviour
in sharks (Sims et al. 2006). Neiva et al. (2006) sug-
gested that E. spinax makes vertical feeding migra-
tions, but further evidence is required to definitively
confirm the behaviour pattern in this genus.
Our study showed that E. pusillus feeds on locally
abundant resources off the Algarve coast. Pasiphaea
sivado, Micromesistius poutassou and myctophids are
key taxa in the regional marine food web (Santos and
Borges 2001). The low trophic diversity of E. pusillus
suggests that it is a selective predator. E. spinax and E.
pusillus have a similar diet in Algarve waters. Fish also
dominated the diet of E. spinax (with M. poutassou
as the most important species) but cephalopods also
played an important role (32.2% by W), particularly
the octopod Eledone sp. (22.6% by W) (Neiva et al.
2006). Neither of these sharks fed on amphipods, salps
or scavenged prey, suggesting a very selective diet,
which contrasts with other shark species, such as Squa-
lus acanthias (Hanchet 1991).
From the prey identified to species level only M.
poutassou seems to play an important role in the diet
of E. pusillus. From the highly digested items, the ce-
phalopod items were small flesh pieces (although some
identifiable beaks were present), the fish were mostly
represented by eroded fish otoliths (seemingly from M.
poutassou but they were too eroded to make a defi-
nite identification) and the crustacean items were too
broken. Although the identified items allowed the diet
of E. pusillus to be interpreted correctly, more feeding
studies are needed, for example, using other methods
such as fatty acid or DNA analyses to identify the
highly digested fish and crustaceans that formed the
bulk of the diet recovered from E. pusillus.
E. pusillus has a similar trophic level (4.3) to other
deep water Squaliformes sharks, including the genera
Somniosus (S. microcephalus, S. pacificus, S. rostra-
tus) and Squalus (S. cubensis, S. megalops), as well as
species in the Etmopterus genus, such as E. baxteri and
E. compagnoi (Cortés 1999).
The frequent observation of a few limited food
items in stomachs, with many prey in advanced stages
of digestion and a relatively high number of empty
stomachs (particularly in specimens collected with
longlines) suggests that E. pusillus feeds intermittently,
as shown for many other sharks in previous studies
(Wetherbee and Cortés 2004, Braccini et al. 2005).
However, more studies on the feeding duration, total
digestion time and gastric evacuation rates of E. pusil-
lus are needed to address this issue.
Diet of E. pusillus according to sex
Sharks could be an appropriate model for testing
theories about the mechanisms underlying sexual
segregation (Sims 2005, Springer 1967). There are
frequently size differences between mature males and
females of the same shark species (Sims 2005). The
fact that most species of sharks have larger females
than males suggests that different energy requirements
are a key cause of sexual segregation (Sims 2005). E.
pusillus matures relatively late in its life cycle and is
sexually dimorphic. Females are larger at first maturity
and reach greater lengths than males (Coelho and Er-
zini 2007). Although E. pusillus may aggregate by size
and sex (Coelho and Erzini 2008b), our study found
no differences between the diets of males and females.
Neiva et al. (2006) also reported a similar absence of
sexual differences in the diets of E. spinax from the
same area. Braccini et al. (2005) reported that Squalus
megalops in southern Australia showed differences in
diets only between large females and smaller males
(which attain lower maximum sizes than females).
Diet of E. pusillus according to ontogenic
development
E. pusillus showed ontogenic changes in dietary
composition, with crustaceans decreasing in impor-
tance and fish progressively increasing in importance
with the size of the sharks (Fig. 3). These diet tran-
sitions are most likely related to the natural increase
in predatory capacity as the shark increases in size.
Larger specimens have larger mouths and stomachs
with greater storage capacity (Karpouzi and Stergiou
2003). An increase in size also implies an increase in
swimming capacity and ability (Wetherbee and Cortés
2004), allowing the sharks to capture larger prey.
In addition to ontogenic changes in the diet of E.
pusillus, there were also differences related to the
sampling gear. For example, in smaller E. pusillus,
Crustacea was quite important in specimens caught by
bottom trawling whereas Natantia was the most impor-
tant in specimens caught with bottom longlines. These
differences can be attributed, despite the overlap, to the
spatial distribution of the sampling according to the
fishing gear (see Fig. 1) and to the characteristics of the
sampling areas, since bottom trawling was performed
on sandy bottoms whereas longlines were set in rocky
areas. As it was not possible to identify the bulk of the
items because they had been heavily digested, more
studies are needed to assess this issue.
Bottom trawling and bottom longlines as methods
for sampling deep-sea sharks
The trawl and longline have considerably different
selectivity (Borges et al. 2001). By combining the data
from the two types of fishing gears, we were able to
test for size-related changes in the diet of E. pusillus.
However, due to our limited dataset, we were unable
to evaluate interactions between sampling year and the
fishing gear used, or to assess the environmental fac-
tors affecting the shark distribution.
FEEDING ECOLOGY OF THE SMOOTH LANTERNSHARK 309
SCI. MAR., 76(2), June 2012, 301-310. ISSN 0214-8358 doi: 10.3989/scimar.03540.07B
Longlines select for individuals in search of food
(Hayward et al. 1989), whose stomachs are likely to be
empty (Simpfendorfer 1998). This might be the cause
of some of the statistical differences that we found
between the gear types. However, longlines caught
larger specimens than bottom trawling, and therefore
the study was able to illustrate a clear change in the
diet of the sharks as they grow (i.e. Crustacea in the
diet of smaller E. pusillus and fish in the diet of larger
E. pusillus). The main sources of bias in trawl-caught
specimens are the lower selectivity of the gear (i.e. the
gear catches a wide size range of organisms) and the
possibility of sharks feeding inside the net. However,
this gear type is less likely to select hungry specimens
than longlines. Our study shows that trawling caught
a wide range of sizes of E. pusillus, with less empty
stomachs (5.7%), in comparison with longlines (nar-
rower range of sizes of E. pusillus and 48.4% of indi-
viduals with empty stomachs), which suggests that the
E. pusillus caught by trawling included specimens that
were hungry. As the prey found inside the stomachs
of E. pusillus were at different stages of digestion (not
necessarily fresh), it is likely that this shark does not
feed substantially inside the net. We concluded that the
two fishing gears used in this study are important for
properly assessing the diet of deep-sea sharks because
they allow sampling across the size distribution, which
is necessary for comprehensively assessing the feeding
ecology of any species. However, further research is
needed in order to critically evaluate the diet of sharks
according to sex and maturity condition at different
spatial and temporal scales (Braccini et al. 2005), as the
number of specimens analysed was not representative.
Implications of this study for the conservation of E.
pusillus
E. pusillus can be caught easily, either by passive
gears (such as longlines) or by active gears (such as
trawling), and therefore conservation issues must be
assessed. Since individuals of this species are never
landed and are not listed in the fisheries statistics, it
is extremely difficult to evaluate population changes
and trends over time (Coelho and Erzini 2005, Coe-
lho and Erzini 2007) and consequently to implement
an effective conservation and management regime in
the future (Coelho and Erzini 2007, Heithaus et al.
2008). Studies like the present one are vital in order to
gather the baseline information necessary for the con-
servation of these poorly understood sharks. We have
shown that, even though E. pusillus is a mesopelagic/
demersal predator, it uses various parts of the water
column and is therefore not exclusively dependent on
benthic resources. Moreover, it is advantageous that
the main prey of E. pusillus have a low commercial
value because the sharks do not actively compete with
commercial fisheries for food resources. However, the
versatile feeding habits of this species make it vulner-
able to many gear types, and therefore it may need
more conservation efforts than species less likely to be
caught as by-catch.
ACKNOWLEDGEMENTS
The authors would like to thank to Dr Margarida
Cristo for her valuable help in identifying crustaceans.
Dr José Xavier and Dr Rui Coelho were supported by
the “FCT - Fundação para a Ciência e Tecnologia”,
co-funded by “POCI-2010 - Programa Operacional
Ciência e Inovação 2010” and “FSE - Fundo Social
Europeu”.
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... Elasmobranchii are highly skilled predators (Holmgren and Nilsson 1999;Lima et al. 2000;Xavier et al. 2012) being at the top of the marine food chain (Gadig 1998;Heithaus et al. 2008;Schwingel and Assunc ßão 2009;Xavier et al. 2012). They have an important role in population control (Camhi et al. 1998;Stevens et al. 2000;Xavier et al. 2012), connecting low and high trophic levels (Ferretti et al. 2010;Heithaus et al. 2010;Bornatowski et al. 2014). ...
... Elasmobranchii are highly skilled predators (Holmgren and Nilsson 1999;Lima et al. 2000;Xavier et al. 2012) being at the top of the marine food chain (Gadig 1998;Heithaus et al. 2008;Schwingel and Assunc ßão 2009;Xavier et al. 2012). They have an important role in population control (Camhi et al. 1998;Stevens et al. 2000;Xavier et al. 2012), connecting low and high trophic levels (Ferretti et al. 2010;Heithaus et al. 2010;Bornatowski et al. 2014). ...
... Elasmobranchii are highly skilled predators (Holmgren and Nilsson 1999;Lima et al. 2000;Xavier et al. 2012) being at the top of the marine food chain (Gadig 1998;Heithaus et al. 2008;Schwingel and Assunc ßão 2009;Xavier et al. 2012). They have an important role in population control (Camhi et al. 1998;Stevens et al. 2000;Xavier et al. 2012), connecting low and high trophic levels (Ferretti et al. 2010;Heithaus et al. 2010;Bornatowski et al. 2014). Therefore, fluctuations in Elasmobranch populations may lead to changes in communities at all trophic levels (Myers et al. 2007;Heithaus et al. 2010). ...
... Deep-sea sharks perform a valuable ecological function maintaining the balance of food webs that support fisheries; however, they are heavily impacted by sustained commercial fishing pressure (Neiva et al., 2006;Xavier et al., 2012). These species are slow growing and late maturing with low fecundities, limiting their capacity to rebound from population impacts such as overfishing (Coelho and Erzini, 2008;Simpfendorfer and Kyne, 2009). ...
... Sharks from Langesund had the largest mean body length (45 cm TL); however the collection method (angling) may have given rise to a size bias favouring larger individuals as has been recorded in comparisons of longline and trawl net sampling in related smooth lanternsharks, Etmopterus pusillus (Xavier et al., 2012). Further sampling may therefore be required to gain insights into demographic structure at Langesund that are representative of the entire population. ...
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Deep-sea sharks play a valuable ecological role helping maintain food web balance, yet they are vulnerable to commercial fishing because of slow growth rates and low reproductive capacity. Overfishing of sharks can heavily impact marine ecosystems and the fisheries these support. Knowledge of stock structure is integral to sustainable management of fisheries. The present study analysed vertebral chemistry using laser ab- lation inductively coupled plasma mass spectrometry (LA-ICP-MS) to assay concentrations of 7Li, 23Na, 24Mg, 55Mn, 59Co, 60Ni, 63Cu, 66Zn, 85Rb, 88Sr, 138Ba and 208Pb to assess stock structure in a deep-sea shark, Etmopterus spinax, in Norwegian and French waters. Few studies have applied this technique to elasmobranch vertebrae and the present study represents its first application to a deep-sea shark. Three stocks were identified at the regional scale off western Norway, southern Norway, and France. At finer spatial scales there was evidence of strong popula- tion mixing. Overall, the general pattern of stock structure outlined herein provides some indication of the spatial scales at which stocks should be viewed as distinct fisheries management units. The identification of an effective multi-element signature for distinguishing E. spinax stocks utilizing Sr, Ba, Mg, Zn and Pb and the methodological groundwork laid in the present study could also expedite future research into stock structure for E. spinax and deep-sea elasmobranchs more generally.
... Like most lanternfishes, they carry out diel vertical migrations (Sassa et al. 2010). Predation on vertically migrating and mesopelagic migrating species is documented in lanternsharks (Neiva et al. 2006;Hallett and Daley 2011;Xavier et al. 2012). However, we believe that G. sauteri does not carry out diel vertical migration for two possible reasons: (1) morphological characteristics, viz. the long low upper caudal lobe with inconspicuous lower caudal lobe in G. sauteri, which are not beneficial for continuous long-distance swimming, thus sustained swimming ability is limited in sharks sharing these morphological characteristics (Scacco et al. 2010); (2) the diet composition, although less important in comparison with lanternfishes and many species of crustaceans, suggests that G. sauteri spends certain time foraging near the seabed. ...
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Small-bodied sharks are recognized as mesopredators on different communities in a large variety of habitats, thus linking the trophic levels in the marine ecosystem. Dietary analysis on these species can provide insight into the trophic relationships in food webs. Our study analyzed the diet composition of Galeus sauteri, an abundant small shark inhabiting neritic shelf waters at depths between 60 and 200 m. For this purpose, a stomach content analysis was realized in 678 specimens collected by bottom trawlers off northeastern Taiwan from September 2018 to August 2019. The two most commonly consumed preys were teleosts (prey-specific index of relative importance, %PSIRI = 51.94) and crustaceans (%PSIRI = 30.08).The results for the Levin's index (Ba = 0.06) and graphical analysis based on the Costello method revealed a high degree of specialization on lanternfishes and other teleosts. The mean trophic position was 4.29. Feeding habits differed significantly in relation to maturity condition and between seasons. Our result showed that G. sauteri is a primary piscivorous shark that preys mainly on lanternfishes and other teleosts, and feeds opportunistically on crustaceans and cephalopods.
... The paradigm of Hg bioaccumulation with growth suggests that a positive correlation between Hg concentrations in muscle tissue and body size in fish can be expected, as Hg has high bioaccumulation potential, but very low detoxification rates (Driscoll et al., 2013;. However, the samples used in the present study were limited to specimens taken as bycatch of bottom trawls fishing for crustaceans, and such gears are likely to be less effective for sampling larger lantern sharks (Xavier et al., 2012). ...
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Mercury (Hg) is a non-essential metal that can have toxic effects on the fitness of organisms and tends to bioaccumulate with age and to biomagnify in higher trophic levels. Few studies have assessed oxidative stress and neurotoxicity in deep-water sharks. This study evaluated early ontogenetic changes and physiological effects (antioxidant defences, oxidative damage, aerobic metabolism and neurotransmission functions) of Hg accumulation in the white muscle and brain tissues of the velvet belly lantern shark Etmopterus spinax from the southern Iberian coast (NE Atlantic). Results suggested that the low mercury concentrations observed may induce acute effects in E. spinax before they reach sexual maturity. We found different Hg concentrations in E. spinax: [Hg] males > [Hg] females; [Hg] muscle > [Hg] brain. Females appeared to have higher redox capability translated into higher activities and levels of antioxidant defences than males. However, higher levels of oxidative damage were also observed in females. Whilst the mechanisms underlying these effects remain unknown, these results suggest differences in mercury accumulation between tissues and sex, and potentially deleterious effects on oxidative stress status and neurophysiology of E. spinax, potentially impairing swimming performance and reproduction, which could subsequently impact on the health of both individuals and population.
... Being a fast swimmer would then represent a significant adaptive advantage if these sharks perform this behavior. Vertical movement of lanternsharks is also supported by the observation of circadian migration for other species of Etmopteridae (Xavier and Vieira, 2012;Neiva et al., 2006) and stomach content analyses which revealed fishes and squids from shallower layers (Daley et al., 2002). However, this circadian migration and the presence of food from near the surface, is also observed for non-luminous deep-sea sharks, such as Centrophorus harrissoni (group Deep C) and Centrophorus squamosus (group Deep B), suggesting that other reasons exist for differences in swimming abilities of deep-sea sharks. ...
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Currently the ecology of deep-water sharks is poorly documented, especially in situ information for these elusive species are lacking. In this study, stereo-Baited Remote Underwater Videos (stereo-BRUVs) were deployed to collect ecological data from New Zealand deep-sea sharks. The results showed differences in abundance between species, with Etmopterus granulosus (Etmopteridae) found in greatest numbers. Moreover, the known depth range increased for Scymnodon macracanthus (Centrophiridae). Deep-sea shark species were generally found to swim at slower cruise speeds (0.36 ± 0.04 m s⁻¹) than their shallow-water counterparts (0.63 ± 0.05 m s⁻¹). However, the swimming speed of deep-sea sharks was clearly not uniform, with some species displaying higher cruise swimming speeds than others. The fastest sharks (Centrophorus harrissoni, Etmopterus granulosus and Etmopterus molleri) had swimming abilities comparable to benthic shallow water sharks (0.48 ± 0.02 m s⁻¹). The higher cruise swimming speed in the family Etmopteridae could be an advantage for these luminous sharks if they follow isolumes to match their ventral light intensity with the down-welling light of their environment. This study revealed that alternative non-destructive methods can be effective for ecological studies of deep-sea marine fauna.
... Ikan dalam pertumbuhannya mengalami perubahan dalam kebiasaan makanannya (Renones et al., 2002;Vögler et al., 2009;Valls et al., 2011;Xavier et al., 2012). Perubahan ontogenetik tersebut merupakan hal yang penting dalam mempelajari ekologi ikan. ...
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Abstrak Penelitian ini bertujuan untuk memaparkan perubahan makanan ikan kurisi berdasarkan ukuran dan musim. Pengambilan contoh dilakukan sekali sebulan dari bulan Agustus 2009 sampai Juli 2010, dengan jaring insang percobaan berukuran mata jaring ¾, 1, 1¼, 1½ inci dan alat seser (garis tengah 1 m dan ukuran mata jaring 0,04 inci). Analisis makanan menggunakan metode indeks bagian terbesar. Jumlah ikan yang terkumpul sebanyak 67 ekor dengan kisaran panjang total antara 46-230 mm dan kisaran bobot antara 2,2-185,5 g. Ikan dikelompokkan ke dalam tiga ukuran yaitu ukuran kecil (46-110 mm), sedang (110,1-170 mm), dan besar (170,1-230 mm). Hasil analisis menunjukkan bahwa menu makanan ikan kurisi berganti seiring dengan perubahan ukuran tubuh. Ikan kurisi berukuran kecil menyukai fitoplankton, Thallasiothrix; kemudian ketika tumbuh membesar (kelompok sedang dan besar), cenderung mengkonsumsi ikan teri (Stolephorus commersonii). Lebih lanjut ditemukan bahwa terjadi perubahan jenis makanan ikan kurisi berdasarkan musim. Abstract The present study aimed to analyze ontogenetic shift in the diet of ornate threadfin bream related to body size and season in Kendari Bay. Monthly sampling was conducted from August 2009 to July 2010. Fish were caught using experimental gillnets with mesh sizes of ¾,1, 1¼, 1½ inch) and push nets (1 m diameter, 0.04 inch mesh). Stomach content analysis was determined using index of preponderance. A total of 67 individual fish were caught with range from 46-230 mm in length and 2.2-185.5 in weight. The fish were grouped into three groups that is small size (46-110 mm), middle (110.1-170 mm); and big (170.1-230 mm). The gut contents showed an ontogenetic shift in diet with an increase in length, small size feeds phytoplankton Thallasiothrix; whereas, middle and big sizes tend to consume Stolephorus commersonii. Moreover, ornate threadfin bream also showed the seasonal diet shift.
... Ikan dalam pertumbuhannya mengalami perubahan dalam kebiasaan makanannya (Renones et al., 2002;Vögler et al., 2009;Valls et al., 2011;Xavier et al., 2012). ...
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Abstrak Penelitian ini bertujuan untuk menganalisis perubahan makanan ikan kurisi berdasarkan ukuran dan musim. Pengambilan contoh dilakukan sekali sebulan dari bulan Agustus 2009 sampai Juli 2010, dengan jaring insang eksperimental berukuran mata jaring ¾ sampai 3 inci dan alat seser (garis tengah 1 meter dan ukuran mata jaring 0,04 inci). Analisis makanan menggunakan metode indeks bagian terbesar. Jumlah ikan yang terkumpul sebanyak 67 ekor dengan kisaran panjang total antara 46-230 mm dan kisaran bobot antara 2,2-185,5 g. Ikan dikelompokkan kedalam tiga ukuran yaitu ukuran kecil (46-110 mm), sedang (110,1-170 mm), dan ukuran besar (170,1-230 mm). Hasil analisis menunjukkan bahwa menu makanan ikan kurisi berganti seiring dengan perubahan ukuran tubuh. Ketika masih kecil ikan menyukai fitoplankton, Thallasiothrix; kemudian ketika tumbuh membesar (kelompok pertengahan dan besar) ikan kurisi makan teri (Stolephorus sp.). Selain itu terdapat perubahan makanan ikan kurisi berdasarkan musim. Abstract This study is aimed to analyzed ontogenic shift on food content of ornate threadfin bream relation of body size of fish with season in Kendari Bay. Sampling collection was carried out monthly from August 2009 to July 2010. The fish was catch using experimental gillnets (with different mesh sizes ¾-3 inch) and push nets (ring diameter 1 meter and mesh size 0.04 inch). Food analysis was determined by using Index of Preponderance.A total of 67 individual fish were caught with range from 46-230 mm in length and 2.2-185.5 in weight. The fish were grouped by three sizes that is small size (46-110 mm), middle (110.1-170 mm); and big size (170.1-230 mm). Result of the analysis indicates is the fish have ontogenetic shift on food content, small size feeds phytoplankton Thallasiothrix; middle and big size choose fish from Stolephorus sp. Beside that, the fish have ontogenetic shift on food content with season. Pendahuluan Ikan kurisi (Nemipterus hexodon) adalah salah satu spesies dominan di perairan Teluk Kendari (Asriyana et al., 2009). Walaupun ikan ini merupakan spesies dominan, namun sejauh ini belum ada penelitian tentang variasi ontogenetik makanan spesies ini  ,
... To gather data representative of natural populations and their densities, identical methods and effort should be employed in collecting samples from different sites. For example, fishery-dependent samples may result in a sampling bias favouring larger individuals, i.e. belonging to older cohorts that may not reflect the entire population (Xavier et al., 2012). In order to reflect natural population densities and distributions, sample sizes should not be set arbitrarily but rather reflect the number of individuals collected at a given site using the same amount of effort used at all sampling sites (Elsdon et al., 2008). ...
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Quantifying the elemental composition of elasmobranch calcified cartilage (hard parts) has the potential to answer a range of ecological and biological questions, at both the individual and population level. Few studies, however, have employed elemental analyses of elasmobranch hard parts. This paper provides an overview of the range of applications of elemental analysis in elasmobranchs, discussing the assumptions and potential limitations in cartilaginous fishes. It also reviews the available information on biotic and abiotic factors influencing patterns of elemental incorporation into hard parts of elasmobranchs and provides some comparative elemental assays and mapping in an attempt to fill knowledge gaps. Directions for future experimental research are highlighted to better understand fundamental elemental dynamics in elasmobranch hard parts.
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548 shark species were considered in this paper. They were classified in function of their depth of occurrence: 218 deep, 114 transitory and 210 shallow. The diets of the 332 deep and transitory species are reviewed. 10 prey categories are recognized here: Chondrichthyes, Teleosts, Cephalopods, Crustaceans, Marine mammals, Annelids, Ctenophores, Egg of Chondrichthyes, Siphonophores, and Bivalves. There is a complete lack of data for 210 species, and 59 have only a limited amount of information available. In general, teleosts, crustaceans, and cephalopods were the main prey found in deep-water sharks. However, some species have a specialized diet. A simple index of dietary knowledge has been developed to highlight the current state of knowledge on the subject, further illustrating the lack of information. The proportion of empty and regurgitated stomachs varies significantly between species and studies. Most data on deep and transitory sharks come from stomach content analysis. Stable isotope analysis provides additional insight into their trophic ecology. Fatty acid profiling and DNA metabarcoding can also add important information, but their use is currently limited with deep-water sharks. The most important conclusion from this synthesis is the lack or scarcity of information for most deep and transitory species.
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The method of collecting and analyzing boluses to characterize the cephalopod diet of albatrosses has been used in many diet studies. However, no study has validated this method. We compared boluses and stomach samples from Gray-headed Albatrosses (Thalassarche chrysostoma) and Black-browed Albatrosses (T. melanophris) to (1) study the consumption and diversity of cephalopods in these species, (2) investigate biases associated with each sampling method, and (3) estimate the number of samples needed to characterize these albatross’s cephalopod diet. We found that collection and analysis of boluses is a simple, efficient, and noninvasive method for assessing the cephalopod diet of these albatross species, but it is inadequate for characterizing the more easily digestible dietary components, such as fish and crustaceans. Both boluses and stomach samples showed that the two albatross species fed on cephalopods of similar sizes and from the same families (Ommastrephidae, Onychoteuthidae, and Cranchiidae). Furthermore, the main prey species (Martialia hyadesi, Kondakovia longimana, and Galiteuthis glacialis) and the total number of cephalopod species consumed (18–24 species) were the same for both albatrosses. To include all cephalopod species, using a sample-randomization technique, a minimum of 61 and 43 boluses were needed for Gray-headed and Black- browed albatrosses, respectively; but to adequately describe the diversity and size frequency of the main prey species, 82 and 371 boluses would be needed. Les Pelotes de Réjection: Une Méthode Efficace pour Évaluer la Proportion de Céphalopodes dans le Régime Alimentaire chez les Albatros
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The impact of fishing on chondrichthyan stocks around the world is currently the focus of considerable international concern. Most chondrichthyan populations are of low productivity relative to teleost fishes, a consequence of their different life-history strategies. This is reflected in the poor record of sustainability of target shark fisheries. Most sharks and some batoids are predators at, or near, the top of marine food webs. The effects of fishing are examined at the single-species level and through trophic interactions. We summarize the status of chondrichthyan fisheries from around the world. Some 50% of the estimated global catch of chondrichthyans is taken as by-catch, does not appear in official fishery statistics, and is almost totally unmanaged. When taken as by-catch, they are often subjected to high fishing mortality directed at teleost target species. Consequently, some skates, sawfish, and deep-water dogfish have been virtually extirpated From large regions. Some chondrichthyans are more resilient to fishing and we examine predictions on the vulnerability of different species based on their life-history and population parameters. At the species level, fishing may alter size structure and population parameters in response to changes in species abundance. We review the evidence for such density-dependent change. Fishing can affect trophic interactions and we examine cases of apparent species replacement and shifts in community composition. Sharks and rays learn to associate trawlers with food and feeding on discards may increase their populations. Using ECOSIM, we make some predictions about the long-term response of ecosystems to fishing on sharks. Three different environments are analysed: a tropical shelf ecosystem in Venezuela, a Hawaiian coral reef ecosystem, and a North Pacific oceanic ecosystem. (C) 2000 International Council for the Exploration of the Sea.
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OVERVIEW Segregation of the sexes within a species is a widespread behavioural phenomenon in both terrestrial and aquatic animals. In the marine realm, sexual segregation is exhibited by many taxa including whales, seals, seabirds and fish. Of the latter group, sharks may be particularly appropriate model animals to test theories on the mechanisms underlying sexual segregation, because sexual segregation is a general characteristic of shark populations, with both sexually dimorphic and monomorphic species being well represented among the approximately 400 extant species (Springer, 1967; Compagno, 1999). The reproductive modes of sharks are diverse ranging from egg-laying (oviparity) to placental live-bearing (viviparity) (Wourms & Demski, 1993). Among sexually dimorphic, viviparous shark species it is generally the female that is larger than the male, whilst in some oviparous species males are larger than females. Sexually monomorphic species also occur. Therefore, sharks possess a number of characteristics that make them an interesting alternative to terrestrial animal models for investigating the causes of sexual segregation. In this chapter the prevalence and nature of sexual segregation in sharks is described and the relationship with reproductive modes is explored. Hypotheses suggested to account for sexual segregation in sharks are examined with respect to new field and laboratory behaviour studies of males and females of a monomorphic species, the lesser spotted dogfish ( Scyliorhinus canicula ). The chapter concludes by drawing together the main points from all shark studies to date, and suggests future directions for research in this area. © Cambridge University Press 2005 and Cambridge University Press, 2009.
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Behavioral activities of a colony of 10 bonnethead sharks, Sphyrna t. tiburo, held under semi-natural conditions, were examined over a period of six months. All sharks had attained, or were approaching, sexual maturity. Objectives of the study were to describe species-typical motor patterns and postures, to analyze the diurnality of patrolling activity and to characterize pattern(s) of organization underlying social interactions noted within the colony. Eighteen postures and patterns of movement were described, almost half of them having apparent social relevance. In specific instances, functional significance of a pattern was cautiously given. Patrolling activity appeared to have a diurnal rhythm, with a peak occurring in the late afternoon; smaller individuals were more erratic in their patrolling. Finally, a clear but subtle social organization, based on a straight-line, size-dependent, dominance hierarchy was found. Though position within the hierarchy was not determined by sex, data indicated that all individuals tended to shy away from larger males. Sexual differences in the performance of certain patterns of movement were also established.
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The diet of a tropical elasmobranch, the lemon shark, Negaprion brevirostris, was investigated through analyses of stomach contents collected during two sampling periods. Data set 1 consisted of the stomach contents of 78 young and sub-adult specimens caught in the Florida Keys and at Bimini, Bahamas, from 1981-85. Data set 2 (n = 86) consisted of newborn and young specimens only, captured in the Florida Keys during the summer of 1986. In the two data sets teleosts were the dominant prey, followed by crustaceans and mollusks. Stomach contents from data set 2 were used to study food consumption parameters and estimate daily ration. About a quarter of the stomachs in each data set were empty. No pattern in diel feeding activity or differences in the amount of food consumed by males or females were found. Feeding in the population was asynchronous and intermittent, with a maximum duration in 11 h. Five methods were applied to determine daily ration. Three of these methods were based upon collection of data on stomach contents of sharks caught in the wild. The other two were laboratory-based approaches. Estimates of daily ration ranged from 1.5-2.1% of the shark's body weight.
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Etmopterus pusillus is a deep water lantern shark with a widespread global distribution that is caught in large quantities in some areas, but is usually discarded due to the low commercial value. In this work, the population biology was studied and life history parameters determined for the first time in this species. Age was estimated from sections of the second dorsal spine and validated by marginal increment analysis. Males attained a maximum age of 13 years, while 17-year-old females were found. Several growth models were fitted and compared for both size and weight at age data, showing that even though this is a small sized species, it has a relatively slow growth rate. This species matures late and at a relatively large size: at 86.81% and 79.40% of the maximum observed sizes and at 58.02% and 54.40% of the maximum observed ages for males and females, respectively. It has a low fecundity, with a mean ovarian fecundity of 10.44 oocytes per reproductive cycle. The estimated parameters indicate that this species has a vulnerable life cycle, typical of deep water squalid sharks. Given the high fishing pressures that it is suffering in the NE Atlantic, the smooth lantern shark may be in danger of severe declines in the near future.