In this study, the length-weight (LWR) parameters were estimated for six syngnathid species, including 2 seahorses and 4 pipefishes, from Ria Formosa, a temperate lagoon from the south coast of Portugal. A total of 5070 fishes were used to determine the LWR. The estimated b value ranged from 2.95 (Nerophis ophidion) to 3.36 (Syngnathus abaster). To the authors' best knowledge, LWR parameters were estimated for the first time for Nerophis ophidion and Syngnathus typhle for the Atlantic waters. Data here present are essential for management and conservation of these flagship species

Bentes, L.

Erzini, Karim

Gonçalves, J. M. S.

Monteiro, P.

Oliveira, F.

Ribeiro, J.

Vieira, RP

Sapientia

IntroductionLength-weight relationships (LWR) concerning syngnathids fromthe southern European Atlantic waters are scarce or inexistent,despite its importance for estimation of the fish condition,predictions of the biomass from length, conversion of growth-in-length equations to growth-in-weight and geographic comparisonsof life histories and morphology of different species (Petrakis &Stergiou, 1995; Gonçalves et al., 1997; Froese & Pauly, 2012).The Ria Formosa lagoon plays a key role as a syngnathidhotspot (Caldwell & Vincent, 2012), therefore is the target ofconservation concerns (Curtis et al., 2007; Shokri et al., 2009). Itis well established that coastal lagoons are highly productivehabitats and appropriate areas for feeding, protection,reproduction and growth of many fish species with high economicand conservational value (Ribeiro et al., 2012). Ria Formosa is atemperate coastal lagoon in southern Europe (Portugal) formed byseveral channels and separated from the sea by sand barrierReçu le 31 juillet 2012 ; accepté après révision le 15 juillet 2013.Received 31 July 2012; accepted in revised form 15 July 2013.Cah. Biol. Mar. (2014) 55 : 9-12Length-weight relationships of six syngnathid species from Ria Formosa, SW Iberian coastRui Pedro VIEIRA, Pedro MONTEIRO, Joaquim RIBEIRO, Luís BENTES, Frederico OLIVEIRA, Karim ERZINI and Jorge Manuel dos Santos GONÇALVESCCMAR - Centro de Ciências do Mar, University of Algarve, Campus de Gambelas, 8005-139 Faro, PortugalE-mail: r.vieira87@gmail.comAbstract: In this study, the length-weight (LWR) parameters were estimated for six syngnathid species, including 2seahorses and 4 pipefishes, from Ria Formosa, a temperate lagoon from the south coast of Portugal. A total of 5070 fisheswere used to determine the LWR. The estimated b value ranged from 2.95 (Nerophis ophidion) to 3.36 (Syngnathusabaster). To the authors’ best knowledge, LWR parameters were estimated for the first time for Nerophis ophidion andSyngnathus typhle for the Atlantic waters. Data here present are essential for management and conservation of theseflagship species.Résumé: Relations taille-poids de six espèces de syngnathidés de Ria Formosa, SW des côtes Ibériques. Dans cette étude,les paramètres taille-poids ont été estimés pour six espèces de syngnathidés, y compris 2 hippocampes et 4 trompettes, deRia Formosa, une lagune de la côte sud du Portugal. Un total de 5070 poissons a été utilisé pour déterminer les relationstaille-poids. La valeur b estimée variait entre 2,95 (Nerophis ophidion) et 3,36 (Syngnathus abaster). A la connaissance desauteurs, les paramètres de LWR ont été estimés pour la première fois pour Nerophis ophidion et Syngnathus typhle dans leseaux atlantiques. Les données présentées ici sont essentielles pour la gestion et la conservation de ces espèces phares.Keywords: Flagship species l Length-weight relationship l Syngnathidae l Temperate lagoon10 ALLOMETRIC RELATIONSHIPS IN SYNGNATHIDS FROM PORTUGALislands. This coastal lagoon is integrated in the Natural Park of RiaFormosa and classified as Natura 2000 site of interest andincluded in the Ramsar Convention (Ribeiro et al., 2008). Six syngnathid species are a common component of theresident ichthyofauna of Ria Formosa (Hippocampus guttulatus,Hippocampus hippocampus, Nerophis ophidion, Syngnathusabaster, Syngnathus acus and Syngnathus typhle). This coastallagoon harbour one of the most abundant and dense syngnathidpopulations (Curtis & Vincent, 2005), but it is also an importantnursery and growth area (Ribeiro et al., 2006, 2008 & 2012). Inaddition, some species have high conservation value at bothnational and international level (e.g., Hippocampus guttulatus,Hippocampus hippocampus, Syngnathus abaster) (ICN, 1993;CITES, 2012; IUCN, 2012; OSPAR, 2012). Material and MethodsSampling was carried out monthly from October 2000 to April2002, with a beach seine for the margins, and beam trawl for themain channels (both with 9 mm mesh size) from a small vessel (6m), as well as a pushnet (for the small channels) (1 mm mesh size)in 41, 12 and 6 stations, respectively, in the Ria Formosa lagoon(Fig. 1). Syngnathid species were released after total or heightlength and wet weight data were recorded to the nearest 0.1 cmand 0.01 g from the specimens collected (Table 1). The estimationof LWR parameters (W = a × TLb; W = a × HLb) were made afterthe logarithmic transformation of the data (log W = log a + b × logTL; log W = log a + b × log HL), where W is wet weight and TLis total length (for pipefishes), HL is height length (for seahorses),a is the intercept and b is the regression coefficient. The degree ofassociation between the weight and length is given by thecoefficient of determination, R2.ResultsA total of 5070 fishes were used to determine the length-weightrelationships of six syngnathid species. Estimated parameters andthe coefficient of determination (R2) are given in Table 1. Sampleswere mainly represented by Hippocampus guttulatus Cuvier, 1829(n = 2042) and Syngnathus typhle Linnaeus, 1758 (n = 1233). Thefish total length size ranged from 3.6 cm for Syngnathus acusLinnaeus, 1758 to 41.4 cm also for S. acus. The wet weight rangedfrom 0.02 g for Syngnathus abaster Risso, 1827 and S. acus to54.57 g for S. acus. Linear regressions fitted to estimate the LWRwere highly significant (P < 0.05) for all species (Table 1). The R2values ranged from 0.950 for H. guttulatus to 0.980 in S. acus. Themedian value of b was 3.23 with a minimum b of 2.95 forHippocampus hippocampus (Linnaeus, 1758) and a maximum bof 3.36 for Syngnathus abaster. In terms of growth, Nerophisophidion (Linnaeus, 1758), Syngnathus abaster, Syngnathus acusand Syngnathus typhle were positively allometric (b > 3),Hippocampus guttulatus showed isometry (b = 3), and H.hippocampus expressed negative allometry (b < 3). SpeciesHL (cm)Weight (g)Parameters of the LWRGrowthtypeMin-MaxMean ± SDMedianMin-MaxMean ± SDMedianNaCI(a)bCI(b)R2Hippocampus guttulatus7.1-16.611.7 ± 1.63 11.70.90-15.825.42 ± 2.4105.0020420.002570.00238-0.002773.093.06-3.120.950IsometricHippocampushippocampus5.0-13.48.3 ± 1.32 8.20.50-8.202.46 ± 1.240 2.224180.004440.00391-0.005032.952.89-3.010.958Allometric -TL (cm)Weight (g)Parameters of the LWRGrowthtypeMin-MaxMean ± SDMedianMin-MaxMean ± SDMedianNaCI(a)bCI(b)R2Nerophis ophidion10.3-19.314.3 ± 2.0914.10.11-0.660.32 ± 0.1390.302690.000070.00005-0.000093.113.03-3.190.951Allometric +Syngnathus abaster3.7-11.07.7 ± 1.157.70.02-1.000.27 ± 0.1430.225790.000250.00022-0.000283.363.31-3.430.956Allometric +Syngnathus acus3.6-41.421.3 ± 6.6820.60.02-54.577.63 ± 7.7444.725290.000200.00017-0.000223.343.30-3.380.980Allometric +Syngnathus typhle4.9-32.315.7 ± 5.1715.00.03-16.951.95 ± 2.1281.0312330.000130.00012-0.000143.353.32-3.370.977Allometric +Table1.Length-weight relationships (LWR) of six syngnathid species from Ria Formosa. HL = height length; TL = total length; Min-Max = minimum and maximum length(cm) and wet weight (g) recorded; SD = standard deviation; N = sample size; aand b = parameters of the length-weight relationship; CI = 95% confidence interval; r2= coefficientof determination. Growth type: Isometric, positive allometry (+), negative allometry (-). R.P. VIEIRA, P. MONTEIRO, J. RIBEIRO, L. BENTES, F. OLIVEIRA, K. ERZINI, J.M. dos Santos GONÇALVES 11DiscussionSpecies of the family Syngnathidae are common species of shal-low waters, and hence LWR were previously obtained for some ofthese species in the SW Iberian (Veiga et al., 2009) andMediterranean coasts (e.g. Verdiell-Cubedo et al., 2006; Gurkan &Taşkavak, 2007) (Table 2). Differences observed for parameterscould be due to spatial variation (Sparre et al., 1989). TheMediterranean Sea shows an oligotrophic nature (Crise et al.,1999; Manca et al., 2004), while the Ria Formosa lagoon is ahighly productive system (Gamito & Erzini, 2005). Consequently,biotic and abiotic features, that control feeding, reproduction andgrowth rates, may play an important role in differences found inthe length-weight parameters between these regions. Besides that,the estimations here present were applied to a larger number ofspecimens, which might also have contributed for differences inthe LWR parameters in different studies. These results represent ayear of sampling and the seasonal variability in fish assemblagesand presence or abundance of juvenile migrants in Ria Formosawere taken into account (Froese, 2006). The parameter b does notvary significantly during the year, while the parameter a couldfluctuate seasonally, daily and between habitats (Gonçalves et al.,1997). These relationships are a result of sampling with specificfishing gears; therefore the application of these allometricparameters must be limited to the observed length ranges (Petrakis& Stergiou, 1995; see also Froese et al., 2011). The data obtained in the present study could be a useful tool inongoing management and conservation studies (Foster & Vincent,2004; Vincent et al., 2011 & 2013), and potentially as a referencefor comparison of similar parameters estimated in other coastallagoons. Measuring merely the length would be adequate toestimate biomasses of these syngnathid without impact suchvulnerable species in a MPA. Sampling in different areas, from the margins to channelsalong the lagoon (see Fig. 1), as well as with different fishinggears allowed to comprise different types of habitats thatcharacterize such complex system as the Ria Formosa coastallagoon (Curtis & Vincent, 2005; Ribeiro et al., 2012). To theauthors’ best knowledge, this is the first report of LWRs forNerophis ophidion and Syngnathus typhle for the Atlantic Ocean.AcknowledgementsThe authors would like to thank our skipper Isidoro Costa and ourcolleagues Pedro Lino, Rui Coelho, Carla Correia, GonçaloCarvalho, Pedro Feijó and Jorge Soares for their valuable helpwith the biological sampling.ReferencesCaldwell I.R. & Vincent A.C.J. 2012. Revisiting two sympatricEuropean seahorse species: apparent decline in the absence ofexploitation. Aquatic Conservation: Marine and FreshwaterEcosystems, 22: 427-435. Figure 1. Map of Ria Formosa lagoon showing samplinglocations and gear types (seine net, pushnet and beam trawl).Study Location Species N a b R2Verdiell-Cubedo et al. (2006) Mar Menor coastal lagoon Hippocampus guttulatus 31 0.00248 2.91 0.916Mar Menor coastal lagoon Syngnathus abaster 1260 0.00068 2.92 0.970Gurkan & Taşkavak (2007) Aegean Sea, Turkey Hippocampus guttulatus 200 0.010 2.47 0.64Aegean Sea, Turkey Hippocampus hippocampus 29 0.001 3.14 0.76Aegean Sea, Turkey Nerophis ophidion 86 3.00E-06 2.42 0.74Aegean Sea, Turkey Syngnathus acus 570 6.00E-08 3.54 0.95Aegean Sea, Turkey Syngnathus typhle 125 3.00E-07 3.00 0.96Veiga et al. (2009) Arade estuary, Southern Portugal Hippocampus guttulatus 84 0.00724 2.71 0.99Arade estuary, Southern Portugal Hippocampus hippocampus 9 0.00640 2.73 0.96Arade estuary, Southern Portugal Syngnathus abaster 57 0.00015 3.53 0.96Arade estuary, Southern Portugal Syngnathus acus 66 0.00020 3.33 0.99Table 2. Length-weight relationships of syngnathids collected from the SW Iberian and Mediterranean Sea. N = sample size; a and b= parameters of the length-weight relationship; R2 = coefficient of determination.CITES 2012. Notification to the Parties No. 2004/003.Concerning Trade in Seahorses Implementation of Decision12.54. Available at www.cites.org (accessed April 2012).Crise A., Allen, J.I., Baretta J., Crispi G., Mosetti R. &Solidoro C. 1999. The Mediterranean pelagic ecosystemresponse to physical forcing. Progress in Oceanography, 44:219-243.Curtis J.M.R. & Vincent A.C.J. 2005. Distribution of sympatricseahorse species along a gradient of habitat complexity in aseagrass-dominated community. Marine Ecology ProgressSeries, 291: 81-91.Curtis J.M.R., Ribeiro J., Erzini K. & Vincent A.C.J. 2007. Aconservation trade-off ? Interspecific differences in seahorseresponses to experimental changes in fishing effort. AquaticConservation: Marine and Freshwater Ecosystems, 17: 468-484. Foster S.J. & Vincent A.C.J. 2004. Life history and ecology ofseahorses: implications for conservation and management.Journal of Fish Biology, 65: 1-61.Froese R. 2006. Cube law, condition factor and weight-lengthrelationships: history, meta-analysis and recommendations.Journal of Applied Ichthyology, 22: 241-253.Froese R. & Pauly D. (eds) 2012. Fishbase. Available atwww.fishbase.org (accessed July 2012).Froese R., Tsikliras A.C. & Stergiou K.I. 2012. Editorial note onweight-length relations of fishes. Acta Ichthyologica etPiscatoria, 41: 261-263. Gamito S. & Erzini K. 2005. Trophic food web and ecosystemattributes of a water reservoir of the Ria Formosa (southPortugal). Ecological Modelling, 181: 509-520.Gonçalves J.M.S., Bentes L., Lino P.G., Ribeiro J., CanárioA.V.M. & Erzini K. 1997. Weight-length relationships forselected fish species of the small-scale demersal fisheries ofthe south and south-west coast of Portugal. Fisheries Research,30: 253-256.Gurkan S. & Taşkavak E. 2007. Length-weigth relationships forsyngnathid fishes of the Aegean Sea, Turkey. Belgian Journalof Zoology, 137: 219-222.ICN 1993. Livro vermelho dos vertebrados de Portugal. Vol. III.Peixes marinhos e estuarinos. Instituto de Conservação eNatureza, Lisboa.IUCN 2012. IUCN Red List of Threatened Species. Version2011.2. Available at www.iucnredlist.org (accessed April2012).Manca B., Burca M., Giorgetti A., Coatanoan C., Garcia M.-J. & Iona A. 2004. Physical and biochemical averaged verticalprofiles in the Mediterranean regions: an important tool totrace the climatology of water masses and to validate incomingdata from operational oceanography. Journal of MarineSystems, 48: 83-116.OSPAR 2012. OSPAR List of Threatened and/or DecliningSpecies and Habitats. (Reference Number: 2008-6). Availableat www.ospar.org (accessed April 2012). Petrakis G. & Stergiou K.I. 1995. Weight-length relationshipsfor 33 fish species in Greek waters. Fisheries Research, 21:465-469. Ribeiro J., Bentes L., Coelho R., Gonçalves J.M.S., Lino P.,Monteiro P. & Erzini K. 2006. Seasonal, tidal and diurnalchanges in fish assemblages in the Ria Formosa lagoon(Portugal). Estuarine, Coastal and Shelf Science, 67: 461-474. Ribeiro J., Monteiro C.C., Monteiro P., Bentes L., Coelho R.,Gonçalves J.M.S., Lino P.G. & Erzini K. 2008. Long-termchanges in fish communities of the Ria Formosa coastal lagoon(southern Portugal) based on two studies made 20 years apart.Estuarine, Coastal and Shelf Science, 76: 57-68. Ribeiro J., Carvalho G.M., Gonçalves J.M.S. & Erzini K.2012. Fish assemblages of shallow intertidal habitats of the RiaFormosa lagoon (South Portugal): influence of habitat andseason. Marine Ecology Progress Series, 446: 259-273.Shokri M.R., Gladstone W. & Jelbart J. 2009. The effectivenessof seahorses and pipefish (Pisces: Syngnathidae) as a flagshipgroup to evaluate the conservation value of estuarine seagrassbeds. Aquatic Conservation: Marine and FreshwaterEcosystems, 19: 588-595.Sparre P., Ursin E. & Venema S.C. 1989. Introduction totropical fish stock assessment. Part I. Manual. FAO FisheriesTechnical Paper No. 306.Veiga P., Machado D., Almeida C., Bentes L., Monteiro P.,Oliveira F., Ruano M., Erzini K. & Gonçalves J.M.S. 2009.Weight-length relationships for 54 species of the Arade estuary,southern Portugal. Journal of Applied Ichthyology, 25: 493-496.Verdiell-Cubedo D., Oliva-Paterna F.J. & Torralva M. 2006.Length-weight relationships for 22 fish species of the MarMenor coastal lagoon (western Mediterranean Sea). Journal ofApplied Ichthyology, 22: 293-294.Vincent A.C.J., Foster S.J. & Koldewey H.J. 2011.Conservation and management of seahorses and otherSyngnathidae. Journal of Fish Biology, 78: 1681-1724.Vincent A.C.J., Sadovy de Mitcheson- Y.J., Fowler S.L. &Lieberman S. 2013. The role of CITES in the conservation ofmarine fishes subject to international trade. Fish and Fisheries.doi: 10.1111/faf.12035.12 ALLOMETRIC RELATIONSHIPS IN SYNGNATHIDS FROM PORTUGAL

Length-weight relationships of six syngnathid species from Ria Formosa, SW Iberian coast

Universidade do Algarve

Introduction
Length-weight relationships (LWR) concerning syngnathids from
the southern European Atlantic waters are scarce or inexistent,
despite its importance for estimation of the fish condition,
predictions of the biomass from length, conversion of growth-in-
length equations to growth-in-weight and geographic comparisons
of life histories and morphology of different species (Petrakis &
Stergiou, 1995; Gonçalves et al., 1997; Froese & Pauly, 2012).
The Ria Formosa lagoon plays a key role as a syngnathid
hotspot (Caldwell & Vincent, 2012), therefore is the target of
conservation concerns (Curtis et al., 2007; Shokri et al., 2009). It
is well established that coastal lagoons are highly productive
habitats and appropriate areas for feeding, protection,
reproduction and growth of many fish species with high economic
and conservational value (Ribeiro et al., 2012). Ria Formosa is a
temperate coastal lagoon in southern Europe (Portugal) formed by
several channels and separated from the sea by sand barrier
Reçu le 31 juillet 2012 ; accepté après révision le 15 juillet 2013.
Received 31 July 2012; accepted in revised form 15 July 2013.
Cah. Biol. Mar. (2014) 55 : 9-12
Length-weight relationships of six syngnathid species from 
Ria Formosa, SW Iberian coast
Rui Pedro VIEIRA, Pedro MONTEIRO, Joaquim RIBEIRO, Luís BENTES, Frederico OLIVEIRA, Karim ERZINI 
and Jorge Manuel dos Santos GONÇALVES
CCMAR - Centro de Ciências do Mar, University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
E-mail: r.vieira87@gmail.com
Abstract: In this study, the length-weight (LWR) parameters were estimated for six syngnathid species, including 2
seahorses and 4 pipefishes, from Ria Formosa, a temperate lagoon from the south coast of Portugal. A total of 5070 fishes
were used to determine the LWR. The estimated b value ranged from 2.95 (Nerophis ophidion) to 3.36 (Syngnathus
abaster). To the authors’ best knowledge, LWR parameters were estimated for the first time for Nerophis ophidion and
Syngnathus typhle for the Atlantic waters. Data here present are essential for management and conservation of these
flagship species.
Résumé: Relations taille-poids de six espèces de syngnathidés de Ria Formosa, SW des côtes Ibériques. Dans cette étude,
les paramètres taille-poids ont été estimés pour six espèces de syngnathidés, y compris 2 hippocampes et 4 trompettes, de
Ria Formosa, une lagune de la côte sud du Portugal. Un total de 5070 poissons a été utilisé pour déterminer les relations
taille-poids. La valeur b estimée variait entre 2,95 (Nerophis ophidion) et 3,36 (Syngnathus abaster). A la connaissance des
auteurs, les paramètres de LWR ont été estimés pour la première fois pour Nerophis ophidion et Syngnathus typhle dans les
eaux atlantiques. Les données présentées ici sont essentielles pour la gestion et la conservation de ces espèces phares.
Keywords: Flagship species l Length-weight relationship l Syngnathidae l Temperate lagoon
10 ALLOMETRIC RELATIONSHIPS IN SYNGNATHIDS FROM PORTUGAL
islands. This coastal lagoon is integrated in the Natural Park of Ria
Formosa and classified as Natura 2000 site of interest and
included in the Ramsar Convention (Ribeiro et al., 2008). 
Six syngnathid species are a common component of the
resident ichthyofauna of Ria Formosa (Hippocampus guttulatus,
Hippocampus hippocampus, Nerophis ophidion, Syngnathus
abaster, Syngnathus acus and Syngnathus typhle). This coastal
lagoon harbour one of the most abundant and dense syngnathid
populations (Curtis & Vincent, 2005), but it is also an important
nursery and growth area (Ribeiro et al., 2006, 2008 & 2012). In
addition, some species have high conservation value at both
national and international level (e.g., Hippocampus guttulatus,
Hippocampus hippocampus, Syngnathus abaster) (ICN, 1993;
CITES, 2012; IUCN, 2012; OSPAR, 2012). 
Material and Methods
Sampling was carried out monthly from October 2000 to April
2002, with a beach seine for the margins, and beam trawl for the
main channels (both with 9 mm mesh size) from a small vessel (6
m), as well as a pushnet (for the small channels) (1 mm mesh size)
in 41, 12 and 6 stations, respectively, in the Ria Formosa lagoon
(Fig. 1). Syngnathid species were released after total or height
length and wet weight data were recorded to the nearest 0.1 cm
and 0.01 g from the specimens collected (Table 1). The estimation
of LWR parameters (W = a × TLb; W = a × HLb) were made after
the logarithmic transformation of the data (log W = log a + b × log
TL; log W = log a + b × log HL), where W is wet weight and TL
is total length (for pipefishes), HL is height length (for seahorses),
a is the intercept and b is the regression coefficient. The degree of
association between the weight and length is given by the
coefficient of determination, R2.
Results
A total of 5070 fishes were used to determine the length-weight
relationships of six syngnathid species. Estimated parameters and
the coefficient of determination (R2) are given in Table 1. Samples
were mainly represented by Hippocampus guttulatus Cuvier, 1829
(n = 2042) and Syngnathus typhle Linnaeus, 1758 (n = 1233). The
fish total length size ranged from 3.6 cm for Syngnathus acus
Linnaeus, 1758 to 41.4 cm also for S. acus. The wet weight ranged
from 0.02 g for Syngnathus abaster Risso, 1827 and S. acus to
54.57 g for S. acus. Linear regressions fitted to estimate the LWR
were highly significant (P < 0.05) for all species (Table 1). The R2
values ranged from 0.950 for H. guttulatus to 0.980 in S. acus. The
median value of b was 3.23 with a minimum b of 2.95 for
Hippocampus hippocampus (Linnaeus, 1758) and a maximum b
of 3.36 for Syngnathus abaster. In terms of growth, Nerophis
ophidion (Linnaeus, 1758), Syngnathus abaster, Syngnathus acus
and Syngnathus typhle were positively allometric (b > 3),
Hippocampus guttulatus showed isometry (b = 3), and H.
hippocampus expressed negative allometry (b < 3). Sp
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6
A
llo
m
et
ric
 +
Sy
ng
na
th
us
 a
cu
s
3.
6-
41
.4
21
.3
 ±
 6
.6
8
20
.6
0.
02
-5
4.
57
7.
63
 ±
 7
.7
44
4.
72
52
9
0.
00
02
0
0.
00
01
7-
0.
00
02
2
3.
34
3.
30
-
3.
38
0.
98
0
A
llo
m
et
ric
 +
Sy
ng
na
th
us
 ty
ph
le
4.
9-
32
.3
15
.7
 ±
 5
.1
7
15
.0
0.
03
-1
6.
95
1.
95
 ±
 2
.1
28
1.
03
12
33
0.
00
01
3
0.
00
01
2-
0.
00
01
4
3.
35
3.
32
-
3.
37
0.
97
7
A
llo
m
et
ric
 +
Ta
bl
e
1.
Le
ng
th
-w
ei
gh
t r
el
at
io
ns
hi
ps
 (L
W
R
) o
f s
ix
 s
yn
gn
at
hi
d 
sp
ec
ie
s 
fr
om
 R
ia
 F
or
m
os
a.
 H
L 
= 
he
ig
ht
 le
ng
th
; T
L 
= 
to
ta
l l
en
gt
h;
 M
in
-M
ax
 =
 m
in
im
um
 a
nd
 m
ax
im
um
 le
ng
th
(c
m
) a
nd
 w
et
 w
ei
gh
t (
g)
 re
co
rd
ed
; S
D
 =
 st
an
da
rd
 d
ev
ia
tio
n;
 N
 =
 sa
m
pl
e 
si
ze
; a
an
d 
b 
=
 p
ar
am
et
er
s o
f t
he
 le
ng
th
-w
ei
gh
t r
el
at
io
ns
hi
p;
 C
I =
 9
5%
 c
on
fid
en
ce
 in
te
rv
al
; r
2
= 
co
ef
fic
ie
nt
of
 d
et
er
m
in
at
io
n.
 G
ro
w
th
 ty
pe
: I
so
m
et
ric
, p
os
iti
ve
 a
llo
m
et
ry
 (+
), 
ne
ga
tiv
e 
al
lo
m
et
ry
 (-
). 
R.P. VIEIRA, P. MONTEIRO, J. RIBEIRO, L. BENTES, F. OLIVEIRA, K. ERZINI, J.M. dos Santos GONÇALVES 11
Discussion
Species of the family Syngnathidae are common species of shal-
low waters, and hence LWR were previously obtained for some of
these species in the SW Iberian (Veiga et al., 2009) and
Mediterranean coasts (e.g. Verdiell-Cubedo et al., 2006; Gurkan &
Taşkavak, 2007) (Table 2). Differences observed for parameters
could be due to spatial variation (Sparre et al., 1989). The
Mediterranean Sea shows an oligotrophic nature (Crise et al.,
1999; Manca et al., 2004), while the Ria Formosa lagoon is a
highly productive system (Gamito & Erzini, 2005). Consequently,
biotic and abiotic features, that control feeding, reproduction and
growth rates, may play an important role in differences found in
the length-weight parameters between these regions. Besides that,
the estimations here present were applied to a larger number of
specimens, which might also have contributed for differences in
the LWR parameters in different studies. These results represent a
year of sampling and the seasonal variability in fish assemblages
and presence or abundance of juvenile migrants in Ria Formosa
were taken into account (Froese, 2006). The parameter b does not
vary significantly during the year, while the parameter a could
fluctuate seasonally, daily and between habitats (Gonçalves et al.,
1997). These relationships are a result of sampling with specific
fishing gears; therefore the application of these allometric
parameters must be limited to the observed length ranges (Petrakis
& Stergiou, 1995; see also Froese et al., 2011). 
The data obtained in the present study could be a useful tool in
ongoing management and conservation studies (Foster & Vincent,
2004; Vincent et al., 2011 & 2013), and potentially as a reference
for comparison of similar parameters estimated in other coastal
lagoons. Measuring merely the length would be adequate to
estimate biomasses of these syngnathid without impact such
vulnerable species in a MPA. 
Sampling in different areas, from the margins to channels
along the lagoon (see Fig. 1), as well as with different fishing
gears allowed to comprise different types of habitats that
characterize such complex system as the Ria Formosa coastal
lagoon (Curtis & Vincent, 2005; Ribeiro et al., 2012). To the
authors’ best knowledge, this is the first report of LWRs for
Nerophis ophidion and Syngnathus typhle for the Atlantic Ocean.
Acknowledgements
The authors would like to thank our skipper Isidoro Costa and our
colleagues Pedro Lino, Rui Coelho, Carla Correia, Gonçalo
Carvalho, Pedro Feijó and Jorge Soares for their valuable help
with the biological sampling.
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12 ALLOMETRIC RELATIONSHIPS IN SYNGNATHIDS FROM PORTUGAL


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Length-weight relationships of six syngnathid species from Ria Formosa, SW Iberian coast

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