Southernmost occurrence of Syngnathus folletti on a temperate coastal lagoon of Argentina

We report the occurrence of a mature male Syngnathus folletti in the inlet channel of Mar Chiquita coastal lagoon (37 8 44 ′ S 57 8 25 ′ W, Buenos Aires, Argentina). This record constitutes the southernmost report for the species. Mar Chiquita coastal lagoon is characterized by mudﬂats surrounded by a large cord-grass area but not by grass beds which are seen to be a suitable habitat for S. folletti . Therefore, oceanic winds that allow warmer northern waters to approach the coast of Argentina could be the cause of the presence of the species.


I N T R O D U C T I O N
The family Syngnathidae is represented by two subfamilies: Hippocampinae (seahorses) and Syngnathinae (pipefish).The former includes one genus and about 36 species; the latter contains 51 genera and at least 196 species (Nelson, 2006).Only one species of Hippocampinae has been reported on the Argentine continental shelf: the seahorse Hippocampus patagonicus (Piacentino & Luzzatto, 2004).Two species of Syngnathinae have been reported in Argentine waters: the deep-bodied pipefish Leptonotus blainvilleanus (Eydoux & Gervais, 1837), with a distribution as far south as Tierra del Fuego; and the southern pipefish Syngnathus folletti (Herald, 1942), which occurs from northern Brazil (near Fortaleza, Ceara ´) to Uruguay and north of Argentina (Dawson, 1982).Syngnathus folletti is a subtropical species found in depths between 10 and 30 m and sporadically at greater depths (83 -200 m) which can support large variations in salinity (Figueiredo & Menezes, 1980), since it has been collected in the Patos Lagoon estuary (Weiss, 1981;Garcia et al., 2001Garcia et al., , 2005)), the middle zone of the Mambucaba River estuary (Neves et al., 2010), as well as in the Rı ´o de la Plata estuary (Ruarte et al., 2009) and the Ajo ´River from its headwater to its mouth in Samborombo ´n Bay (36820 ′ -36828 ′ S 56854 ′ -56859 ′ W), in the nearby Rı ´o de la Plata estuary (Solari et al., 2009).We report here the occurrence of S. folletti in the inlet channel (37844 ′ S 57825 ′ W) about 1000 m from the mouth of the Mar Chiquita coastal lagoon (Buenos Aires, Argentina).This record constitutes the southernmost report for the species.

M A T E R I A L S A N D M E T H O D S
One specimen of Syngnathus folletti was collected on 15 December 2008 by a local fisherman with a 1.70 m diameter, 20-mm mesh size landing net equipped with a 5-mm mesh size cod-end, during the high tide at nightfall.The specimen was frozen for four months before being fixed in 10% formalin, identified and measured to the nearest 0.05 mm with a digital caliper.The specimen is registered in the collection of the Instituto Nacional de Investigacio ´n y Desarrollo Pesquero as INIDEP No. 825.

R E S U L T S
The specimen of Syngnathus folletti was a mature male (Figure 1).Morphometric features and body proportions are summarized in Table 1, and agree with those reported by other authors who described this species (e.g.Herald, 1942;Pozzi & Siccardi, 1948).

D I S C U S S I O N
The occasional presence of tropical and subtropical teleost fish in Mar Chiquita coastal lagoon has been attributed to the incursion of warm neritic waters to the Argentine continental shelf (Dı ´az de Astarloa et al., 2000;Figueroa et al., 2000;Gonza ´lez Castro et al., 2006;Blasina et al., 2009) in combination with winds from the oceanic region that allow marine water to enter several kilometres into the inner channel (Reta et al., 2001).Lucas et al. (2005) stated that the Rı ´o de la Plata discharge (22,000 m 3 s 21 ) has a weak seasonal signal in discharge volume with a maximum in the winter and a minimum in the summer.In the summer months, prevailing onshore winds force the low salinity signal south and east along the Argentine coast as far as 378S (Lucas et al., 2005).The weather forecast for December 2008 developed by the Servicio Meteorolo ´gico Nacional (Skansi, 2008) showed a scarce rainfall period with negative anomalies and a sea surface temperature of two degrees above average.The low rainfall could reduce the Rio de la Plata discharge and oceanic winds allowed warmer northern waters to approach the coast of Argentina, explaining the increase in sea surface temperature.This unusual atmospheric phenomenon could explain the southernmost distribution of Syngnathus folletti.Garcia & Vieira (1997) and Garcia et al. (2005) showed that Widgeon grass beds seem to be a suitable habitat for the species where S. folletti can feed and reproduce.Mar Chiquita coastal lagoon is characterized by mudflats surrounded by a large cord-grass (Spartina densiflora) area (Fasano et al., 1982;Martinetto et al., 2007) but not by grass beds.Despite the importance of this coastal lagoon as a refuge and feeding ground for juvenile fish during their critical development stages and also as a stopover site for adult fish along their migratory routes (Cousseau et al., 2001;Gonza ´lez Castro et al., 2009;Valin ˜as et al., 2010) it seems not to be a suitable environment for S. folletti.This emphasizes that the unusual atmospheric phenomenon could be the cause of the presence of the species.
A C K N O W L E D G E M E N T S The authors would like to thank Miguel Addino for donating the specimen, Gabriela Silvoni from INIDEP who kindly provided relevant literature and Dra.Marı ´a Berta Cousseau for her valuable suggestions on the earlier version of this manuscript.Daniel O. Bruno and Mariana Addino were supported by scholarships from CONICET.R E F E R E N C E S Blasina G.E., Delpiani S.M., Bruno D.O., Gonza ´lez Castro M. and Dı ´az de Astarloa J.M. (2009) First record of Callorhinchus callorynchus and Trachurus lathami, in a south-western Atlantic coastal lagoon.Marine Biodiversity Records 2, e90.Cousseau M.B., Dı ´az de Astarloa J.M. and Figueroa D.E. (2001) La Ictiofauna de la Laguna Mar Chiquita.In Iribarne O. (ed.) Reserva de Bio ´sfera Mar Chiquita: caracterı ´sticas fı ´sicas, biolo ´gicas y ecolo ´gicas.Mar del Plata: Editorial Martı ´n, pp.187-203.