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Keywords
Hemigrammus mahnerti, La Plata basin, Moenkhausia
bonita, Paraguay River.
Abstract
Despite the high fish diversity of the Paraguay basin,
there is still large uncertainty about the presence and dis-
tribution of species in the country of Paraguay. Here, I pre-
sent an annotated checklist to the fish of Paraguay’s only
true lake, Laguna Blanca, in San Pedro department, based
on samples collected opportunistically between 2012 and
2017. A total of 32 species from 16 families and 6 orders
were found, although the actual total is estimated at be-
tween 36 and 58 species. This included an unnamed
species of Hemigrammus and the first country record of
Moenkhausia bonita. Live colouration is also described for
Hemigrammus mahnerti. One species was endemic to
Paraguay, four to the Paraguay river basin, eight to the
Paraná-Paraguay and 15 to the Rio De La Plata, whilst two
were potamodromous. Species composition is typical of
Neotropical lentic systems but with a distinct scarcity of
benthivores, likely associated with the oligotrophic condi-
tions of the lake. The threats to this unique ecosystem,
through uncontrolled development, illegal deforestation,
pollution and overfishing are imminent and recommenda-
tions for its protection are given.
Zusammenfassung
Obwohl es in der Fischfauna des Paraguay-Beckens eine
starke Vielfalt gibt, bestehen nach wie vor große Un-
klarheiten darüber, welche Arten in welcher Verbreitung
im Land Paraguay vorkommen. An dieser Stelle präsen-
tiere ich eine kommentierte Checkliste der Fischfauna des
einzigen echten Binnensees Paraguays, der Laguna Blanca
im Department San Pedro – auf der Grundlage von Bele-
gen, die ich zwischen 2012 und 2017 unsystematisch
gesammelt habe. Insgesamt konnte ich 32 Arten in 16
Familien und 6 Ordnungen nachweisen, obwohl die
Schätzungen bei 36 bis 58 Arten liegen. Zu den
nachgewiesenen Arten zählen eine unbenannte Hemigram-
mus-Art und der erste Landes-Nachweis von Moenkhausia
bonita. Von Hemigrammus mahnerti wird die Lebendfär-
bung beschrieben. Eine Art ist endemisch für Paraguay, vi-
er sind endemisch für das Paraguay-Flussbecken, acht für
Paraná-Paraguay und 15 für den Rio De La Plata, während
zwei Arten potamodrom sind (süßwasser-bezogene Wan-
derfische). Die Artenzusammensetzung entspricht der für
neotropische lentische Systeme (stehende Gewässer) typis-
chen, allerdings ist die benthivore Ernährung (von boden-
bewohnenden Wirbellosen) eingeschränkt, was wahrsch -
einlich mit den oligotrophen (nährstoffarmen) Bedingun-
gen des Sees zu tun hat. Die Bedrohung dieses einzigarti-
gen Ökosystems ist stark – durch unkontrollierte Entwick-
lung, illegale Abholzung, Verschmutzung und Überfis-
chung. Vorschläge zum Schutz werden gemacht.
Sommario
Nonostante l'elevata diversità ittica del bacino del
Paraguay, permangono grandi incertezze sulla presenza e la
distribuzione delle specie nel Paraguay. Qui, presento un
elenco commentato dei pesci dell’unico vero lago del
Paraguay, la Laguna Blanca, nel dipartimento di San Pe-
dro, sulla base di campioni raccolti a tale scopo tra il 2012
e il 2017. Sebbene il totale effettivo sia stimato tra 36 e 58
specie, sono state rinvenute 32 specie appartenenti a 16
famiglie e 6 ordini. Tra queste si trova una specie di Hem-
igrammus non ancora descritta e la prima segnalazione a
livello nazionale di Moenkhausia bonita. É anche descritta
la colorazione nativa di Hemigrammus mahnerti. Una
specie era endemica del Paraguay, quattro nel bacino del fi-
ume Paraguay, otto nel Paraná-Paraguay e 15 nel Rio De
La Plata, mentre due erano potamodromiche. La compo-
sizione delle specie è tipica dei sistemi lentici ma con una
netta carenza di bentivori, probabilmente associata alle
condizioni oligotrofiche del lago. Le minacce a questo eco-
sistema unico, attraverso lo sviluppo incontrollato, la de-
aqua vol. 25 no. 4 - 15 October 2019
155
aqua, International Journal of Ichthyology
Annotated checklist to the fish of Laguna Blanca, San Pedro, Paraguay
Jeremy Kenneth Dickens
Fundación Para La Tierra, Centro IDEAL, 321 Mariscal José Félix Estigarribia,
c/ Teniente Capurro, Barrio General Diaz, Pilar, Departamento de Ñeembucú, Paraguay.
Email: Jeremy@paralatierra.org, jerdickens@gmail.com
Received: 19 June 2019 – Accepted: 10 October 2019
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 155
forestazione illegale, l'inquinamento e la pesca eccessiva
sono pressanti e vengono fornite raccomandazioni per la
sua protezione.
INTRODUCTION
The Neotropics have the highest freshwater fish
diversity on earth with over 5,160 known species
(Nelson et al. 2016; Reis et al. 2016), although
new species are still being described at a rate of
around 104 per year (Reis et al. 2016), leading to
total estimates of over 8,000 (Reis 2013; Reis et al.
2003). At the heart of the region, lies the small
land-locked country of Paraguay, which covers four
distinct freshwater ecoregions leading to an excep-
tional level of diversity. This includes the Paraguay
basin with 344 fish species, of which over 80 are
endemic (Hales & Petry 2015a), the Lower Paraná
with 340 species, 35 endemic (Hales & Petry
2015b), the Upper Paraná with 265, 131 endemic
(Hales & Petry 2015c), and Chaco with 150
species, 16 endemic (Hales & Petry 2015d). Even
though these are some of the best-studied systems
in South America, there is still a large degree of un-
certainty with regards to the species present and
the ranges occupied by each within the country of
Paraguay itself with only 307 species included in
the Checklist of the Fishes of Paraguay (CLOFPY)
(Koerber et al. 2017). This differs substantially in
number and the species listed from online reposi-
tories, including 283 species in fishbase.se and 395
in faunaparaguay.com. The sparsity of the informa-
tion available is also evident in the large number of
species listings excluded from the CLOFPY due to
the lack of physical evidence, even though the pres-
ence of some, such as Zungaro jahu, Luciopimelodus
pati and Pinirampus pirinampu, is considered ‘ob-
vious’ by regional experts (Flávio Lima, pers.
comm.). On the other hand, other species have
been wrongfully included, including those that do
not occur in the basin, such as Scleromystax
macropterus, or that are taxonomically invalid, such
as two of the three listed Megalonema species
(Flávio Lima, pers. comm.). It is also evident in the
numerous new species descriptions (Albert &
Crampton 2003; Axenrot & Kullander 2003; Car-
doso et al. 2016; Calegari et al. 2011, 2017; Costa
2006; Craig et al. 2017; Fernandes et al. 2005;
Géry & Mahnert 1993; Huber 1995; Knaack
2003; Kullander 2009; Kullander & Lucena 2013;
Lucinda et al. 2005; Malabarba 2004; Mahnert &
Géry 1987, 1988; Ota et al. 2015; Reis et al. 1992;
Reis & Pereira 2000; Retzer & Page 1997; Říčan &
Kullander 2008; Rosso et al. 2016; Thomas et al.
2013; Vera Alcaraz et al. 2008; Weber 1985, 1986,
1987; Weitzman 1985) and new records (e.g. Lo-
boda 2016; Lucinda 2017; Vera Alcaraz et al.
2017) to emerge from the region in recent decades.
In this context, Laguna Blanca is distinct from the
surrounding ecosystems, which consist mostly of
large nutrient-rich and sediment-laden floodplain
rivers and wetlands (Hales & Petry 2015a; Quirós
2003). It is Paraguay’s only true lake and charac-
terised by crystal clear oligotrophic water (Acevedo
et al. 1990), similar to the recharge lakes of the
Brazilian Pantanal (Costa et al., 2015; Furian et al.
2013) over 300 km to the north. Other South
American lakes include the Patagonian glacial
lakes, saline systems of the southern cone basin
complex and high Andean systems (Reis et al.
2016), whilst the largest tropical system is Lake
Maracaibo, which varies from swampy to estuarine
habitats.
In light of its unique nature, an inventory of fish
species of the lake is necessary. A handful of sam-
ples were previously collected at nearby localities
during the National Biological Inventory Project
(IBN) by members of the Paraguayan, Geneva and
Stockholm Museums between 1981 and 1989
(Ramlow 1989; Weitzman 1985) but only four
species are cited as being from the lake itself (Uj &
Géry 1989; Géry et al. 1987). The specimens col-
lected during these expeditions were deposited in
the Museo de Historia Natural de Paraguay
(MNHNP), Natural History Museum of Geneva
(MHNG), Swedish Museum of Natural History,
Stockholm (NRM), United States National Muse-
um (USNM) and University of Michigan Museum
of zoology (UMMZ). Several of these have resulted
in new species descriptions (Lucinda et al. 2005;
Uj & Géry 1989; Weber 1986; Weitzman 1985).
However, longer term and more continuous collec-
tion collection efforts at Laguna Blanca only began
with the establishment of an ecological station be-
longing to Fundación Para La Tierra (PLT) be-
tween 2010 and April 2017 at Rancho Laguna
Blanca. Herein, we aim to provide a list of all the
species present in this unique lake and its immedi-
ate surroundings.
MATERIALS AND METHODS
Study Area
Laguna Blanca (23°48’S 56°16’W, 200 m.a.s.l.)
(Figure 1) is situated in the Santa Rosa del Aguaray
district, department of San Pedro, eastern Paraguay
aqua vol. 25 no. 4 - 15 October 2019 156
Annotated checklist to the fish of Laguna Blanca, San Pedro, Paraguay
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 156
in the equatorial dry-winter (Aw) Köppen-Geiger
climate zone (Kottek et al. 2006) with a mean an-
nual temperature between 22 and 23° C and mean
rainfall between 1400 and 1500 mm. It lies on the
boundary between the deep white fluvisols of the
Cerrado, which create the spectacular white-sand
beaches giving the lake its name, and the red ulti-
sols of the Alto Paraná Atlantic Forest (Jiménez &
Torres 2017). The lake has an area of 1.6 km2,
perimeter of 6.0 km and maximum depth of 8 m
and is fed by water filtering through the deep sands
so is exceptionally clear, oligosaline, oligotrophic
and slightly acidic with a prominent thermocline.
Its depth, thermal stratification and insular ecology
led it to be declared Paraguay’s only true lake
(Acevedo et al. 1990). It is also a recharge point for
the Guaraní Aquifer – the largest in the world. In
wet years water drains down a small ephemeral
stream into the Mboreví swamp along the Aguaray
Guazú River and flows into the Jejuí Guazú River-
a tributary to the middle Paraguay River. The habi-
tats of the lake consist of the pelagic zone (open
water), surrounded by a narrow band of emergent
vegetation, dominated by Eleocharis sp., the adja-
cent shallows, both marshy and sandy beach (Fig-
ure 2) and the lake outlet, which has flowing water
when water levels are high. Additional sampled
habitats in the immediate surrounds include a shal-
low seasonal pond (< 1 m deep) situated in the At-
lantic forest about 250 m from the southern corner
of the lake. Following heavy rains in 2015, flood-
ing (< 0.3 m deep) covered large tracts of open
campo limpo habitat in the Cerrado with pools re-
maining until the termination of the project in
2017. These were kept separate from the lake by a
slightly higher strip of land along the northwestern
boundary of the lake characterised by mesophytic
gallery forest on inceptisols.
Data collection
Staff and members of the Fundación Para La Tier-
ra (PLT) sampled fish opportunistically between
10 May 2012 and 9 April 2017 across Laguna
Blanca, in the affluent stream and seasonal ponds
aqua vol. 25 no. 4 - 15 October 2019
157
Jeremy Kenneth Dickens
Fig. 1. Map of Laguna Blanca and sampling localities.
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 157
and rainwater pools in the bordering Atlantic For-
est and Cerrado habitats on Rancho Laguna Blan-
ca. This long time frame included short periods of
greater effort. The first between 11 February and
31 March 2013, when sampling was carried out at
four evenly spaced points along 4 transects across
the width of the lake, alternating between the use
of gillnets and bottle traps at each as well as seine-
netting in shallower water and hand netting oppor-
tunistically. The second, between 08 to 29 April
2014 involved a comprehensive survey of the lake
fish using all available capture techniques [gill nets
(15 cm and 2.5 cm mesh diameters), seine nets,
dip nets and bottle traps] across all habitats of the
lake. This was continued between 25 July 2016
and 09 April 2017. A project comparing the diets
of S. maculatus and H. malabaricus in the lake be-
tween 06 June and 02 August 2016 also resulted in
incidental captures and specimens were also occa-
sionally acquired from local fisherman. Specimens
were fixed either in 10 % formaldehyde solution or
70% ethanol and later preserved in 70% ethanol
and deposited in the Colección Científico de Para
La Tierra – Ictiología (CCPLT), housed at the
Centro IDEAL de la Fundación Para La Tierra in
Pilar, Ñeembucú department, Paraguay. Tissue
samples were taken of most those fixed in formalin
after the 06 June 2016.
All specimens were identified to the lowest possible
taxonomic level using taxonomic keys and the avail-
able scientific literature (Almirón et al. 2015; Benine
et al. 2004, 2009; Lucena & Soares 2016; Lucinda
aqua vol. 25 no. 4 - 15 October 2019 158
Annotated checklist to the fish of Laguna Blanca, San Pedro, Paraguay
Fig. 2. Cross section of Laguna Blanca (not to scale) on a general southwest to northeast direction, showing the division of
major aquatic habitats. A = Open Water, B = Emergent Vegetation, C = Shallows, D = Outlet/Outlet stream (lotic), E = flood-
ed Cerrado, F = Seasonal Forest Pond.
Fig. 3. a) Interpolated (solid line) and extrapolated (broken line) species rarefaction curves with 95 % confidence intervals
and b) actual species accumulation curve of fish collected at Laguna Blanca.
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 158
et al. 2005; Melo & Buckup 2006; Neris et al. 2010;
Ota et al. 2018; Peixoto et al. 2015; Sarmento-
Soares & Martins-Pinheiro 2008; Uj & Géry 1989;
Vari 1991; Weitzman 1985). Smaller characters
were inspected and counts made under a stereo-mi-
croscope (AmScope SZMT2). Morphometric mea-
surements were taken with callipers (precision ±
0.02 mm) or a standard rule for distances > 15 cm.
Data analysis
I aggregated the number of lots per species and es-
timated the total number of species, bootstap stan-
dard error (100 repeats), lower and upper 95 %
confidence limits as well as the number of unde-
tected species and sample coverage of fish in Lagu-
na Blanca using the superduplicates method out-
lined in Chao et al. (2017). This uses Good-Turing
theory to provide a reliable estimate of the number
of doubletons based solely on the total number of
species and the number recorded only once (single-
tons), enabling the estimation of the above indices
and plotting of rarefaction- extrapolated curves us-
ing the iNEXT package (Hsieh et al. 2016) run in
R software (R Development Core Team 2015).
Mapping was carried out in QuantumGIS.
RESULTS
We collected 138 lots (514 individuals) of 32
species from 16 families and 6 orders, with 11 sin-
gletons. The estimated total number of species is
43 with a confidence interval between 36 and 58
species, standard error of 4.9 and 11 species (25 %)
remaining undetected (Figure 3). Sample coverage
was good with a mean of 92.8 % and confidence
interval of 89.3 to 96.2 %. Characiformes were the
most species rich order with 17 species (53 %), fol-
lowed by the Siluiformes with 5 species (16 %), Ci-
chliformes, Gymnotiformes and Cyprinodontif-
ormes each with three species (9 %) and a single
species of Synbranchiformes. The greatest number
of species were collected in the lake outlet (17), fol-
lowed by an equal number in the shallows and
emergent vegetation (14), flooded Cerrado (6),
open water (5) and, lastly, the seasonal forest pond
(2) (Table I). Two species were only collected in
open water, three in emergent vegetation, three in
the shallows, four in the lake outlet, two in the
flooded Cerrado and none in the forest pond
(Table II).
Below is the annotated checklist to the fish of La-
guna Blanca.
aqua vol. 25 no. 4 - 15 October 2019
159
Jeremy Kenneth Dickens
Fig. 4. Number of species per order present in Laguna Blanca.
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 159
No. Locality Latitude Longitude Source
1 Agro forestal Rio Verde, Dist. de Santa Rosa del Aguaray -23.74697 -56.32004 Orig.
2 Beach shore, San Pedro,Paraguay -23.81383 -56.29459 Est.
First beach, San Pedro,Paraguay -23.81383 -56.29459 Est.
Lake Shore Beach, San Pedro,Paraguay -23.81383 -56.29459 Est.
3 N Lake, 280 m from reeds, San Pedro,Paraguay -23.80346 -56.27914 Est.
4 N Shore, Laguna Blanca, Santa Rosa del Aguaray -23.80825 -56.28516 Orig.
5 Near Outlet, Laguna Blanca (Emergent Vegetation near lake Outlet) -23.81337 -56.29464 Orig.
6 NW corner, Laguna Blanca (Edge of emergent vegetation) -23.81300 -56.29446 Orig.
7 Outlet Stream, Laguna Blanca (Flat sandy bed in small clearwater stream (lentic)) -23.81288 -56.29509 Orig.
Outlet Stream, Laguna Blanca (Lotic, small clearwater stream) -23.81288 -56.29509 Orig.
Outlet Stream, Laguna Blanca (Lake Outlet Stream) -23.81288 -56.29509 Est.
Stream by bridge, Laguna Blanca (Lake Outlet Stream) -23.81288 -56.29509 Est.
Stream, near bridge, San Pedro,Paraguay -23.81288 -56.29509 Est.
8 Outlet, Laguna Blanca (Lake Outlet Stream) -23.81288 -56.29501 Orig.
Outlet, Laguna Blanca (Lake Outlet) -23.81288 -56.29501 Orig.
Outlet, Laguna Blanca (Lake Outlet, edge of marsh) -23.81288 -56.29501 Orig.
9 Outlet, Laguna Blanca (Lake Outlet Stream, under overhanging vegetation) -23.81276 -56.29537 Orig.
10 Outlet, Laguna Blanca -23.81327 -56.29482 Orig.
Outlet, Laguna Blanca (Lake edge with extensive bed of submerged -23.81327 -56.29482 Orig.
vegetation, <60cm deep)
11 Outlet, Laguna Blanca (Lake Outlet Stream & Marshy Lakeshore) -23.81304 -56.29486 Orig.
12 Outlet, Laguna Blanca (Lake Outlet, edge of marsh) -23.81331 -56.29480 Orig.
Outlet, Laguna Blanca (Lake Outlet, edge of marsh) -23.81311 -56.29480 Orig.
Outlet, Laguna Blanca (Marshy Lakeshore) -23.81337 -56.29480 Orig.
13 R1 Center, San Pedro,Paraguay -23.81375 -56.29232 Est.
14 R1 Left side, San Pedro,Paraguay -23.81264 -56.29288 Est.
15 R2 Left side, San Pedro,Paraguay -23.81047 -56.28826 Est.
16 R2 Rightside, San Pedro,Paraguay -23.81368 -56.28705 Est.
17 R4 Leftside, San Pedro,Paraguay -23.80323 -56.28093 Est.
18 Rancho Laguna Blanca (Small Pool (1x1.5m x 0.5m deep) -23.77695 -56.29134 Orig.
in temporarily Flooded Cerrado)
19 Rancho Laguna Blanca (Temporarily Flooded Cerrado.) -23.79637 -56.29045 Orig.
20 Rancho Laguna Blanca (Temporarily Flooded Cerrado. Water <20cm deep) -23.77887 -56.29219 Orig.
21 Seasonal Pond, Rancho Laguna Blanca (Seasonal Pond in Atlantic Forest) -23.81716 -56.29035 Orig.
22 Second beach, San Pedro,Paraguay -23.81489 -56.29420 Est.
2nd Beach 10m off shore, San Pedro,Paraguay -23.81489 -56.29420 Est.
23 Second cove, Laguna Blanca -23.81561 -56.29280 Est.
24 S Corner, Laguna Blanca (Emergent Vegetation) -23.81415 -56.29424 Orig.
South Bank, Laguna Blanca, R.N. Laguna Blanca -23.81529 -56.29218 Orig.
Southern corner of Laguna Blanca, R.N. Laguna Blanca -23.81529 -56.29218 Orig.
(Lake edge extensive submerged riparian vegetation)
Southern corner of Laguna Blanca, Santa Rosa del Aguaray -23.81529 -56.29218 Orig.
Laguna Blanca (Emergent Vegetation) -23.81415 -56.29424 Orig.
25 W shore, Laguna Blanca (Emergent Vegetation) -23.81415 -56.29424 Orig.
26 Warm shallows , Laguna Blanca (Warm Shallows) -23.81294 -56.29479 Est.
aqua vol. 25 no. 4 - 15 October 2019 160
Annotated checklist to the fish of Laguna Blanca, San Pedro, Paraguay
Table I. List of specimen collection localities and habitat in parentheses, GPS coordinates and source (original, or estimated
from description). Those with generic locality information as “Laguna Blanca” were not mapped.
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 160
Characiformes
Anostomidae
Leporinus lacustris Amaral Campos 1945 (Fig. 5a)
The possession of 33 lateral scales separate it from
Megaleporinus. Deep body (3.2 of SL) and three
blotches with the first more pigmented than the
rest separate it from L. friderici (Ota et al. 2018).
This omnivorous species occurs in the Paraguay
and Upper Paraná basins and differs from many of
its congeners by preferring lentic habitats (Britski
& Birindelli 2008). Previously recorded by Géry et
al. (1987).
Material: • 1 subadult; Santa Rosa del Aguaray,
Laguna Blanca, N Shore; -23.80825° S -56.28516°
W; 28 June 2016; PLT exped.; Gill Net; formalin;
tissue collected (pectoral fin); CZPLT-I 0036 • 1
subadult; R4 Leftside; 31 March 2013; PLT ex-
ped.; CZPLT-I 0030
Characidae
Bryconinae
Brycon hilarii (Valenciennes 1850) (Fig. 5b)
Only a single mature specimen was recorded of
this benthopelagic potamodromous species of the
Paraguay, middle Paraná and upper Amazonas sys-
tems (Lima 2017). It is an important record, given
its commercial value. As a migratory species, it is
almost certainly a visitor to the lake entering when
water levels in the outlet stream are high with indi-
viduals subsequently becoming trapped when wa-
ter levels drop. The lack of juvenile specimens after
five years of sampling suggest that they do not
breed in the lake but this cannot be ruled out.
Material: • 1 adult; R1 Left side; 10 March 2013;
PLT exped; CZPLT-I 0026
Salminus brasiliensis (Cuvier 1816) (Fig. 5c)
This popular angling species known locally as the
‘dorado’ of the Paraná, Paraguay, Uruguay, Cha-
paré, Mamoré and Laguna dos Patos basins is well
known to carry out long-distance migrations be-
tween spawning grounds in the river headwaters
and lower reaches. Facing overfishing in Paraguay,
a complete ban was placed on catches for five years
to enable the stocks to recover. Although regularly
seen jumping in the pelagic zone the only con-
firmed record of this species is a photo of a mature
individual (c. 6kg) captured whilst being attacked
by a Green Anaconda Euneces murinus in the shal-
lows between 7 and 11 June 2011 (the markings of
the attack are clearly visible on the caudal pedun-
cle). Given its commercial value and role as a top
predator, its presence in the lake is important. It is
almost certainly a visitor, only entering the lake
when water levels in the outlet stream are suffi-
ciently high. The lack of juvenile specimens after
aqua vol. 25 no. 4 - 15 October 2019
161
Jeremy Kenneth Dickens
Table II. Species recorded in each of the major habitats in and around the Laguna Blanca.
A B C D E F
Open water Emergent veg. Shallows Outlet Flooded Cerrado Forest Pond
L. lacustris A. rutilus A. lacustris A. lacustris A. lacustris P. australis
B. hilarii A. lacustris B. aff. melanurus B. aff. melanurus H. unitaeniatus C. dimerus
S. brasiliensis B. aff. melanurus Hemigrammus sp H. elachys P. australis
S. maculatus H. mahnerti M. bonita M. bonita M. punctatus
R. quelen M. bonita H. unitaeniatus M. australis N. paraguayensis
H. malabaricus H. malabaricus S. brevipinna C. callichthys
S. maculatus P. australis H. malabaricus
E. aff. trilineata P. psittakos P. australis
S. macrurus M. punctatus M. punctatus
C. dimerus G. c. australis E. aff. trilineata
C. lepidota S. macrurus S. macrurus
T. aff. coriaceus C. dimerus C. dimerus
R. quelen R. aurata L. dorsigera
S. marmoratus S. marmoratus C. lepidota
T. neivai
R. aurata
S. marmoratus
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 161
five years of sampling and appropriate lotic breed-
ing habitat suggest that they do not breed in the
lake but this cannot be ruled out.
Stethaprioninae
Astyanax rutilus (Jenyns 1842) (Fig. 5d)
The broad silver longitudinal stripe, elongated
humeral spot, more than 25 anal rays, origin of
dorsal fin half way between tip of snout and caudal
fin, third infraorbital not covering cheek, black bar
extending from posterior end of caudal peduncle
to end of central three caudal fin rays and aligned
predorsal scales place this species in the A. fasciatus
(Cuvier 1819) complex (Melo & Buckup 2006).
However, as A. fasciatus is now known to be re-
stricted to the São Francisco, those from De La
Plata likely correspond to A. rutilus (Casciotta et al.
2005), as recognised by Koerber et al. (2017), but
a taxonomic revision of the complex is required to
verify this. Therefore, we tentatively place this
species as A. rutilus but note that the lateral scale
count is lower than observed for A. fasciatus, 33-38
(vs. 38-41). Branched anal-fin rays number 25-27
(2). The live colouration (Figure 5d) consisted of a
very shiny silver body with a broad silver longitu-
dinal stripe; faint vertically-elongated humeral spot
made up of diffuse dark chromatophores and a
black bar extending from the posterior end of cau-
dal peduncle to the end of the central three caudal
fin rays. Paired fins were hyaline tinted yellow; dor-
sal fin yellow becoming hyaline at tip; anal fin yel-
low along basal half; caudal fin yellow at base, be-
sides for the three central rays, extending to the
posterior edge nearer the middle but most of the
outer region of the caudal fin lobes hyaline. A gen-
eralist predator, it was slightly less common than
the more aggressive A. lacustris but captured to-
gether with it in the shallows along the beach and
lake outlet as well as in the stands of emergent veg-
etation along the lake edge.
Material: • 3 inds.; First beach; 13 February
2013; PLT exped.; CZPLT-I 0007/0008/0011. • 2
inds.; Laguna Blanca; 25 April 2014; PLT exped.;
CZPLT-I 0085. • 1 adult; S. Corner, Laguna Blan-
ca; 23.81415° S 56.29424° W; caught at 1 m
depth, water 3 m deep; 14 February 2017; 16:00-
20:00; Jeremy K. Dickens leg.; Emergent Vegeta-
tion; Gillnet; EtOH; CZPLT-I 0107. • 3 adult;
same as preceding, preserved in formalin; CZPLT-
I 0108.
Astyanax lacustris (Lütken 1875) (Figs 5e, f)
This species clearly corresponds to the A. bimacu-
latus “caudal peduncle spot” subgroup , due to the
possession of the caudal spot and oval humeral
spot. It is identified as A. lacustris of the La Plata
basin by having 36-38 (2) scales on the lateral line
and 25-28 (2) branched anal rays (Lucena &
Soares 2016). The morphology of this species is
notoriously variable and we observed two different
morphotypes present at Laguna Blanca. Specimens
from throughout the lake typically had yellow fins,
sometimes quite vivid (Figure 5e). The body was
silver with a dark spot at the posterior end of each
scale, darker brown dorsally. However, a sample
collected from a shoal found in a small pool in the
flooded Cerrado (Figure 5f) had bright red fins
when alive. The head shape was also more concave
than those from the lake. The lateral line scale
count of 36-39 (2) and anal fin ray count of 27-29
branched rays (2) were similar. These floodwaters
were connected to the Aguaray-Guazu River just
north of Rancho Laguna Blanca, where they were
also previously recorded by Ramlow (1989).
Therefore, the morphometric differences suggest
that the lake population differs from those in the
surrounding drainages. Although various authors
have suggested the species-level distinction of vari-
ous populations a comprehensive morphometric
analysis by Lucena & Soares (2016) was unable to
justify these splits. We therefore, tentatively place
both morphotypes as A. lacustris as their possible
taxonomic differences require further investiga-
tion. It is an aggressive small predator and larger
individuals were sometimes caught on baited
hooks. Sometimes used as bait by local fishermen.
Material: • 1 adult; First beach, 13 February
2013; PLT exped.; CZPLT-I 0010 • 3 inds.; Lagu-
na Blanca, Outlet; 23.81288° S 56.29501° W; 0.5
deep; 04 March 2017, 21:00; Jeremy K. Dickens
leg.; Lake Outlet; Dipnet; formalin; CZPLT-I
0132 • 2 inds.; same as preceding, preserved in
EtOH; CZPLT-I 0650 •3 inds.; Laguna Blanca,
Outlet; 23.81288° S; 56.29501° W; 0.5 deep; 05
m deep; March 2017; 08:00; PLT exped.; Lake
Outlet Stream; Dipnet; formalin; CZPLT-I 0653
•5 inds.; same as preceding; preserved in EtOH;
CZPLT-I 0654 •3 inds.; same locality; 11 March
2017; 09:00; Jeremy K. Dickens leg.; Lake Outlet
Stream; Dipnet; EtOH; CZPLT-I 0655 •5 adults;
Rancho Laguna Blanca; 23.77695° S; 56.29134°
W; 17 September 2016; Jeremy K. Dickens and
Paul Smith leg.; small Pool (1x1.5m x 0.5m deep)
in temporarily flooded Cerrado; Dipnet; EtOH;
CZPLT-I 0057/ 0063 to 0066.
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AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 162
Bryconops aff. melanurus (Bloch 1794) (Fig. 5n)
Although this species was considered to be re-
stricted to the coastal drainages of the Guiana
Shield by Lima et al. (2003), it was listed in the
CLOFPY based on a record from the Rio Tagatiyã
in the Concepción department (close to the Pan-
tanal) by Neris et al. (2008). However, the external
morphology of this specimen is identical to those
from the Pantanal, which have been studied in de-
tail by Sidlauskas et al. (2006) and differ from the
nominate by the greater extension of black onto
the dorsal half of the caudal fin (vs. black restricted
as a stripe on the central rays) (Chernoff et al.
1994). The population in Laguna Blanca, however,
differs even further by possessing a distinctive red
area on the basal half of the upper caudal fin, ex-
tending from the black to the fin edge (vs. no red)
as well as the red dorsal and adipose fins. Further
investigation is therefore required into the varia-
tion within the species. This was one of the most
regularly caught species in traps and gillnets and is
heavily exploited by local fishermen as bait.
Material: • 1 adult; First beach; 13 February
2013; PLT exped.; CZPLT-I 0009 • 17 adults; La-
guna Blanca; 23.81415° S 56.29424° W; caught at
1 m deep, water depth 3 m; 14 February 2017;
16:00-20:00; Jeremy K. Dickens; Emergent Vege-
tation; Gillnet; Formalin; CZPLT-I 0111 •3 im-
matures; Laguna Blanca, Outlet; 23.81288° S
56.29501° W; 0.5 m deep; 04 March 2017; 21:00;
Jeremy K Dickens; Lake Outlet; Dipnet; Formalin;
CZPLT-I 0130 •12 individuals; same as preceding;
EtOH; CZPLT-I 0648 •6 adults; Laguna Blanca,
second beach, 14 February 2013; PLT exped.; CZ-
PLT-I 0015 to 0019/0021 •2 adults; Laguna Blan-
ca, stream by bridge; 10 April 2014; PLT exped.;
Lake Outlet Stream; CZPLT-I 0071.
Hemigrammus mahnerti Uj & Géry 1989
(Figs 5h, i)
Identified by the ellipse-shaped caudal spot with
a rounded posterior margin extending only onto
the base of the caudal fin, two thin stripes at anal
fin base, large eye (2.3-2.6 of SL), 6 perforated lat-
eral line scales, and iii (1) – iv (2) plus 19 (2)-20
(1) anal-fin rays. This species has only been record-
ed from tributaries of the Lower Paraguay and
Paraná. The holotype originated from close by, in
the “estero 3 km al Noroeste de Lima” and a single
paratype is listed as originating from Laguna Blan-
ca (Uj & Géry 1989). Large shoals of several hun-
dred individuals were observed inhabiting the
emergent vegetation along the edge of the lake
(pers. obs.).
Live colouration (Figure 5i): Dorsal half of body
olive green, darker above head and dorsal surface of
peduncle between adipose and caudal fins; ventral
half of body transparent; viscera silvery-white but
with prominent postabdominal black spot; black
caudal spot with round posterior edge and concave
along dorsal and ventral halves of anterior edge, ex-
tending into thin black stripe as far anteriorly as
the vertical through the insertion of the first dor-
sal-fin ray; thin black line at base of anal and dorsal
fins, second very thin black line along base of inte-
rior-extensions of anal rays; paired fins and caudal
fin hyaline; dorsal and anal fins hyaline with yellow
along the basal three-quarters of the three to four
anteriormost rays.
Material: • 26, mixed sexes and sizes; Laguna
Blanca, Near Outlet; 23.81337° S 56.29464° W;
1m deep; 14 February 2017; 18:00; Jeremy K.
Dickens leg.; emergent vegetation near lake outlet;
seine net; formalin; tissue sample taken; CZPLT-I
0110.
Hyphessobrycon elachys Weitzman 1985 (Fig. 5g)
Easily recognised by the broad anterior anal fin
lobe of mature males, elongated second to fourth
rays of the dorsal fin, black caudal spot covering
the posterior half of the caudal peduncle and nasal
portion of the caudal fin and small size (<19.7
mm) (Weitzman 1985). The holotype and some
paratypes of this species originate from very close
by, in the “estero 3 km al Noroeste de Lima” within
the Rio Aguaray-Guazu drainage (Weitzman
1985). It is endemic to the Paraguay River in
Paraguay and Brazil. The clear water outlet stream
habitat in which these specimens were collected
differs notably from the habitat preference given in
the species description for turbid waters covered in
floating vegetation.
Material: • 9 adults; Laguna Blanca, Stream by
bridge; 10 April 2014; PLT exped.; Lake Outlet
Stream; CZPLT-I 0070.
Hemigrammus sp. (Fig. 5j)
Two individuals of an unidentified tetra (Figure
5k) were collected in the marshy shallows near the
lake outlet. They do not match any known species
descriptions with an unusual horizonally or verti-
cally oblong humeral patch with rounded edges.
The lateral line was incomplete with 9-13 perforat-
ed scales and 33-34 in the longitudinal series, 6 se-
aqua vol. 25 no. 4 - 15 October 2019
163
Jeremy Kenneth Dickens
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 163
aqua vol. 25 no. 4 - 15 October 2019 164
Annotated checklist to the fish of Laguna Blanca, San Pedro, Paraguay
Figs 5a-n. Characiformes of Laguna Blanca – Anostomidae and Characidae: a) Leporinus lacustris, b) Brycon hilarii, c) Salmi-
nus brasiliensis, d) Astyanax rutilus, e) Astyanax lacustris (yellow morph), f) Astyanax lacustris (red morph), g) Hyphessobrycon
elachys, h) Hemigrammus mahnerti (preserved), i) Hemigrammus mahnerti (live), j) Hemigrammus sp., k) Moenkhausia bonita
(preserved), l) Moenkhausia bonita (live), m) Moenkhausia australis, n) Bryconops aff. melanurus.
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 164
ries above and 8 below the lateral line. Anal-fin ray
counts were iii.23-25 and dorsal rays 10-11. The
measurements were: standard length 34.5-45, head
8-7, body depth at insertion of dorsal fin 11-9.8
and eye diameter 2mm. SL/D: 3.1-3.4, SL/HL:
4.3-5.0 and eye/HL: 0.25-0.29.
Material: • 2 adults; Laguna Blanca, Outlet;
23.813039° S 56.294856° W; 1m deep; 14 Febru-
ary 2017; 18:00; Jeremy K. Dickens leg.; Lake
Outlet Stream & Marshy Lakeshore; Seine net;
Formalin; CZPLT-I 0113.
Moenkhausia bonita Benine, Castro & Sabino
2004 (Figs 5k, l)
Although only recently described, this species is
now recognised as widespread throughout the La
Plata basin (Vanegas-Ríos et al. 2019). Past records
of M. intermedia Eigenmann, 1908, which were
excluded from the CLOFPY due to the lack of sup-
porting evidence can most likely be attributed to
this species. Indeed, further downstream, in Ar-
gentina, listings of M. intermedia can now be at-
tributed to M. bonita, following the examination
of extensive samples identified as M. intermedia in
Argentine collections by Vanegas-Ríos et al.
(2019). It was very common in the littoral zone of
the lake and together with B. melanurus was one of
the most regularly caught species in traps and heav-
ily exploited by local fishermen as bait. Vanegas-
Ríos et al. (2019) determined that the body dimen-
sions of M. bonita are highly variable between
drainage systems. Indeed, the dimensions of the
Laguna Blanca population are unique. The depth
at dorsal fin origin is 3.33 (3.03-3.74), head length
4.20 (3.92-4.67) of standard length (n = 9). The
eye diameter is 2.31 (2.23-2.35) and snout 3.97
(3.54-4.48) of head length (n = 3).
Material: • 95 individuals; Laguna Blanca, Out-
let; 23.813039° S 56.294856° W; 1 m deep; 14
February 2017; 18:00; Jeremy K Dickens; Lake
Outlet Stream & Marshy Lakeshore; Seine net;
Formalin; tissue sample taken; CZPLT-I 0103 •
10inds; Laguna Blanca, Outlet; 23.81288° S
56.29501° W; 0.5 m deep; 4 March 2017; 21:00;
Jeremy K Dickens; Lake Outlet Stream; Dip net;
EtOH; CZPLT-I 0651 •5 adults; Laguna Blanca,
Stream by bridge; 08 April 2014; PLT exped.; Lake
Outlet Stream; CZPLT-I 0069.
Moenkhausia australe Eigenmann 1908 (Fig. 5m)
Species of ‘red-eyed tetras’ are easily distinguished
by lateral line counts and the number of scale rows
above and below. Although Lima et al. (2003) con-
sidered M. sanctaefilomenae to be the only red-eyed
species to occur in the Paraguay River a detailed ex-
amination by Benine et al. (2009) revalidated M.
australe from Paraguay. The complete lateral line
with 28 scales, 5 rows above and 4 below, as well as
the reticulated body pattern diagnose our speci-
mens as this species. All specimens were collected
in flowing water in the lake outlet.
Material: • 2 inds.; Laguna Blanca, Outlet;
23.81288° S 56.29501° W; 0.5 m deep; 04 March
2017; 21:00; Jeremy K. Dickens leg.; Lake Outlet;
Dip net; Formalin; CZPLT-I 0131 • 1 ind; same as
preceding, EtOH; CZPLT-I 0649.
Curimatidae
Steindachnerina brevipinna (Eigenmann & Eigen-
mann 1889) (Fig. 6a)
Unmistakable colour pattern with black patch in
dorsal fin and thin black longitudinal stripe distin-
guishes it against other curimatids (Vari 1991). A
small detritivore, it is found in the Paraguay,
Paraná and Uruguay basins. A single specimen was
collected in the outlet stream.
Material: • 1 adult; Laguna Blanca, Outlet;
23.81288° S 56.29501° W; 0.5 m deep; 04 March
2017; 21:00; Jeremy K. Dickens leg.; Lake Outlet;
Dip net; Formalin; CZPLT-I 0129.
Erythrinidae
Hoplerythrinus unitaeniatus (Spix & Agassiz 1829)
(Fig. 6b)
Unmistakable by head pattern. A widespread
Neotropical piscivore, it was commonly found in
shallows along the lakeshore, where it was often
caught with baited hooks. It was also plentiful in
the flooded Cerrado. At night it was often found in
water <10 cm deep.
Material: • 1 adult; First beach; 14 February
2013; PLT exped.; line fishing; CZPLT-I 0014 • 1
ind; Laguna Blanca; 25 April 2014; PLT exped.;
night fishing with spotlight and dipnet; CZPLT-I
0081 • 4 ind.; Rancho Laguna Blanca; 23.77695°
S 56.29134° W; 17 September 2016; Jeremy K.
Dickens and Paul Smith leg.; Small Pool (1x1.5m
x 0.5m deep) in temporarily Flooded Cerrado; Dip
net; EtOH; Tissue collected (left pelvic fin); CZ-
PLT-I 0058/0060 to 0062.
Hoplias malabaricus (Bloch 1794) (Fig. 6c)
Identified by the lack of distinctive transverse
stripes on ventral view of head, 38-39 lateral line
scale, 13-14 dorsal-fin rays, 6 gill rakers on the first
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165
Jeremy Kenneth Dickens
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epibranchial and toothed plates on the basihyal
and basibranchials (i.e. rough tongue) (Azpelicueta
et al. 2015; Rosso et al. 2016). Previously recorded
by Géry et al. (1987). This widespread Neotropical
piscivore, typically associated with densely vegetat-
ed lentic and lotic habitats was caught throughout
the lake, especially in vegetated and shallow water
areas and was targeted by local fishermen.
Material: • 2 adults; First beach; 18 February
2013; PLT exped.; CZPLT-I 0023/0024 • 1 adult;
Laguna Blanca; 23.81415 °S -56.29424° W;
Caught at 1 to 2 m depth, water depth 3 m; 14
February 2017; 16:00-20:00; Jeremy K Dickens;
Emergent Vegetation; Gillnet; Formalin; tissue col-
lected (left pelvic fin); CZPLT-I 0112 • 1 Juvenile;
Laguna Blanca, Outlet; 23.81288° S 56.29501°
W; 0.5 m depth; 04 March 2017; 21:00; Jeremy K.
Dickens leg.; Lake Outlet; Dip net; Formalin; CZ-
PLT-I 0128 • 2 adults; R.N. Laguna Blanca,
Southern corner of Laguna Blanca; 23.81529° S
56.29218° W; 02 August 2016; PLT exped.; Lake
edge with extensive submerged riparian vegetation;
Gillnet; Formol; tissue collected (left pelvic fin);
CZPLT-I 0047/0048.
Lebiasinidae
Pyrrhulina australis Eigenmann & Kennedy 1903
(Fig. 6d)
Distributed throughout the La Plata basin and
Guaporé drainage, this omnivorous species was
common in the shallows along the lakeshore, par-
ticularly marshy areas. Vast numbers were also
found in the flooded Cerrado and it was one of on-
ly two species present in the seasonal pond in the
Atlantic Forest. Previously recorded by Géry et al.
(1987).
Material: • 5 ind.; Dist. de Santa Rosa del
Aguaray, Agro forestal Rio Verde; 23.74697° S
56.32004° W; 25 July 2016; Jeremy K Dickens
leg.; caught by hand; Formol; tissue collected
(whole ind.): CZPLT-I 0040 • 3 adult; Laguna
Blanca, Outlet; 23.81337° S 56.29480° W; 0.3 m
deep; 14 February 2017; 18:00; Jeremy K. Dickens
leg.; Marshy Lakeshore; Seine net; formalin; CZ-
PLT-I 0105 • 7 adults; same as preceding; EtOH;
CZPLT-I 0106 • 112 ind; Rancho Laguna Blanca;
23.77887° S 56.29219° W, 0.2 m deep; 17 Sep-
tember 2016; Jeremy K. Dickens and Paul Smith
leg.; Temporarily flooded Cerrado; dipnet; EtOH;
tissue collected (6 whole individuals); thousands
present in temporary pools covering large tracts of
the Cerrado that has been flooded for at least 4-5
months; CZPLT-I 0055 • 2 adults; Rancho Laguna
Blanca, Seasonal Pond; 23.81716°S 56.29035° W;
0.1 m deep; 15 February 2017; 21:00;Jeremy K
Dickens leg.; Seasonal Pond in Atlantic Forest; dip-
net; EtOH; CZPLT-I 0109 • 4 inds; Laguna Blan-
ca, Stream by bridge; 08 April 2014; PLT exped.;
Lake Outlet Stream; CZPLT-I 0067.
Serrasalmidae
Pygocentrus nattereri Kner 1858 (Fig. 6e)
Only a single specimen of this typically shoaling
carnivore exists from the lake, identified by the
rounded anterior edge of the head and mostly
black tail besides for a lighter area proximal to the
posterior margin (Fink 1993). It is widely distrib-
uted across South America east of the Andes and
has variable colouration. The individual in ques-
tion is blackish with iridescent bronze to light blue
reflections in the scales. Far less common than S.
maculatus in the lake.
Material: 1 subadult; Laguna Blanca, Second
cove; 23 April 2014; PLT exped.; small gillnet;
CZPLT-I 0076.
Serrasalmus maculatus Kner 1858 (Figs 6f, g)
Identified by the light concavity in the dorsal pro-
file of the head and black submarginal stripe in the
caudal fin. This species is distributed throughout
the Paraguay-Paraná and Amazon rivers (Jégu &
Santos 2001) and was one of the most frequently
caught predators in the lake, targeted by local fish-
ermen for food. Most individuals were immatures
and subadults, caught in or near the emergent veg-
etation along the lakeshore but adults ventured in-
to the pelagic zone with one individual caught 280
m from the nearest structure.
Material: • 1 juvenile; First beach; 13 February
2013; PLT exped.; CZPLT-I 0012 • 1 adult; Lagu-
na Blanca; 06 June 2016; PLT exped.; Gillnet; For-
mol, tissue collected (skeletal muscle); CZPLT-I
0054 • 1 adult; N Lake, 280 m from reeds; 05
March 2013; PLT exped.; CZPLT-I 0025 • 1
subadult; Laguna Blanca, NW corner; 23.81300°
S 56.29446° W; caught at 1-2 m depth, water 3 m
deep; 14 February 2017; 16:00-20:00; Jeremy K.
Dickens leg.; Edge of emergent vegetation; Gillnet;
formalin; tissue collected; CZPLT-I 0097 • 1 juve-
nile; Second beach, 14 February 2013; PLT exped.;
CZPLT-I 0013 • 4 juveniles; Laguna Blanca, Sec-
ond cove; 23 April 2014; PLT exped.; small gillnet;
CZPLT-I 0083 • 1 juvenile; R.N. Laguna Blanca,
Laguna Blanca, South Bank; 23.81529° S
aqua vol. 25 no. 4 - 15 October 2019 166
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AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 166
aqua vol. 25 no. 4 - 15 October 2019
167
Jeremy Kenneth Dickens
Figs 6a-g. Characiformes of Laguna Blanca – Curimatidae, Erythrinidae, Lebiasinidae and Serraslmidae: a) Steindachenrina
brevipinna, b)Hoplerythrinus unitaeniatus, c) Hoplias malabaricus, d) Pyrrhulina australis, e) Pygocentrus nattereri, f) Ser-
rasalmus maculatus (adult), g) Serrasalmus maculatus (juvenile).
56.29218° W; 15 June 2016; PLT exped.; Gillnet;
Formol; stomach removed for study of contents;
CZPLT-I 0042 • juveniles; Southern corner of La-
guna Blanca; 23.81529° S 56.29218° W; 14 July
2016; PLT exped.; Gillnet; Formol, tissue collected
(anal fin, liver); stomach removed for study of con-
tents; CZPLT-I 0032 • 2 juveniles; same as preced-
ing, EtOH; CZPLT-I 0037 • 1 juvenile; same as
preceding; Formol, tissue collected (anal fin); CZ-
PLT-I 0038 • 1 juveniles; Laguna Blanca, W shore;
23.81415° S 56.29424° W; caught at 1 to 2 m
depth, water 3 m deep; 14 February 2017; 16:00-
20:00; Jeremy K. Dickens; Emergent Vegetation;
Gillnet; Formalin; tissue collected (left pectoral
fin); CZPLT-I 0098 • 6 juveniles; Laguna Blanca,
W shore; 23.81415° S 56.29424° W; caught at 1-
2 m depth, water 3 m deep; 14 February 2017;
16:00-20:00; Jeremy K Dickens; Emergent Vegeta-
tion; Gillnet; Formalin; CZPLT-I 0114 to 0119.
Cyprinodontiformes
Poeciliidae
Phallotorynus psittakos Lucinda, De Souza Rocha
& Reis, 2005 (Fig. 7a)
Only recently described, the holotype and several
paratypes for this Paraguayan endemic guppy were
collected from the vicinity of Laguna Blanca by B.
Delling (18 March & 19 October 1998) and G.
Taylor (22 July 1979) (Lucinda et al. 2005). It is
restricted to the floodplains on the east bank of the
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 167
Lower Paraguay between San Pedro and Misiones
departments. Although males are unique in having
a very large lateral process at the base of fifth me-
dian anal-fin radial, females are diagnosed by the
single large lateral spot and 8 dorsal rays. This pro-
vides the first record from the lake itself, with a sin-
gle individual seine netted in the marshy shallows.
Material: • 1 ; Laguna Blanca, Warm shallows;
24 April 2014; PLT exped.; CZPLT-I 0084.
Rivulidae
Melanorivulus punctatus Boulenger, 1895
(Figs 7b, c)
Dozens of this killifish were collected in the lake
shallows, especially marshy areas, as well as in the
flooded Cerrado. It is diagnosed by its spatula-
shaped caudal fin, red dots covering the body that
are not arranged in bars or stripes, lack of red bars
or orange stripes in caudal fin and 30-32 lateral
line scales (Costa 1995, 2005; Schindler & Etzel
2008). The colour pattern is highly variable, as
shown by Schindler & Etzel (2008) and we show
two morphotypes (Figure 7b & c). It is distributed
in the Paraguay, lower Paraná and middle Uruguay
drainages (Costa 2003).
Material: • 1 adult; Dist. de Santa Rosa del
Aguaray, Agro forestal Rio Verde; 23.74697° S
56.32004° W; 25 July 2016; Jeremy K Dickens
leg.; Caught by hand; Formol; CZPLT-I 0041 • 8
inds.; Laguna Blanca, Outlet; -23.81288° S
56.29501° W; 09 April 2017; PLT exped.; Lake
Outlet Stream; Dipnet; CZPLT-I 0656 • 27 inds.;
Rancho Laguna Blanca; 23.79637° S 56.29045°
W; 0.3 m deep; 10 February 2017; PLT exped.;
temporarily flooded Cerrado.; dipnet; formalin;
tissue collected (whole Individuals); CZPLT-I
0092 • 4 inds.; Laguna Blanca, Warm shallows; 15
April 2014; PLT exped.; no; N/A; CZPLT-I 0079
• 3 inds.; same as preceding; CZPLT-I 0080.
Neofundulus cf. paraguayensis (Eigenmann &
Kennedy 1903) (Fig. 7d)
A single specimen was tentatively identified as
this species by the presence of several reddish-
brown longitudinal stripes (Costa 2015; Nielsen &
Brousseau 2013). However, the tip of the pelvic fin
does not extend as far posterior as is typical of this
species but may be due to the immature nature of
the specimen. It was collected in flooded Cerrado
amongst thousands of Pyrrhulina australis and is
endemic to the Paraguay basin in Paraguay and
Brazil.
Material: • 1 ind.; Rancho Laguna Blanca;
23.77887° S 56.29219° W; 0.2 m deep; 17 Sep-
tember 2016; Jeremy K. Dickens and Paul Smith
leg.; Temporarily Flooded Cerrado; Dipnet;
EtOH; found together with thousands of Pyrrhuli-
na australis (including CZPLT-I 0055) present in
temporary pools covering large tracts of the Cerra-
do that had been flooded for at least 4-5 months;
CZPLT-I 0056.
Gymnotiformes
Gymnotidae
Gymnotus carapo australis Craig, Crampton & Al-
bert, 2017 (Fig. 7e)
Distinguished from conspecifics by possessing 25
obliquely-oriented dark brown bands with wavy
margins and about three times as broad the paler
interbands, slender body (73 % of HL), slender
head (58 % of HL) and longer head (11 % of TL).
The species is found throughout South America
east of the Andes, with the subspecies restricted to
the La Plata basin (Craig et al. 2017, 2018). A noc-
turnal ambush predator, the only specimen was
collected in the vegetated areas along the lake edge,
typical of their preferred swampy and headwater
habitats (Albert 2001; Craig et al. 2018).
Material: • 1 adult; Laguna Blanca; 25 April
2014; PLT exped.; night fishing with spotlight and
dipnet; CZPLT-I 0087.
Sternopygidae
Eigenmannia aff. trilineata López & Castello
1966 (Fig. 7f)
Species of the E. trilineata glass knifefish complex
are identified by their transparent colouration and
the presence of a dark superior midlateral stripe.
Following a revision by Peixoto et al. (2015) the
complex was shown to contain a large number of
cryptic species. The nominate form was shown to
occur in the La Plata basin, however, no specimens
from Paraguay were investigated. Compared to tri-
lineata (sensu Peixoto et al. (2015) the body depth
at pectoral fin insertion is lower (12-14 vs. 16 -20),
posterior naris to orbit distance greater (16-17 vs.
4.8-9.3 %) and caudal filament depth greater (3.4-
3.9 % vs. 1.9-3.0 %), whilst the range of the body
depth at anal fin insertion is lower (11-16 vs. 13.6-
18.4 %), orbital diameter lower (14-20 vs. 15.3-
21.6 %), caudal filament length greater (31-49 vs.
19.8-37.1 %) and head depth at orbit greater (61-
72 vs. 55.4-71.7 %). The greater suborbital depth
(32-36 %) rules out E. desantanai, a species from
aqua vol. 25 no. 4 - 15 October 2019 168
Annotated checklist to the fish of Laguna Blanca, San Pedro, Paraguay
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 168
the Upper Paraguay. Therefore, it is likely an unde-
scribed taxon. Members of this complex are crepus-
cular insectivores (Giora et al. 2005) with all speci-
mens captured at night in well-vegetated shallower
areas along the lake edge, including the outlet.
Material: • 1 adult; Laguna Blanca; 29 April 2014;
PLT exped.; night fishing with spotlight and dip-
net; CZPLT-I 0090 • 1 adult; Laguna Blanca, Out-
let; 23.81327° S 56.29482° W; 0.6 m deep; 05 Au-
gust 2016; Jeremy K. Dickens leg.; Lake edge with
extensive bed of submerged vegetation, <60cm
deep; Dipnet; Formol, tissue collected (left pectoral
fin); CZPLT-I 0053 • 1 adult; Laguna Blanca ,
Outlet; 23.81288° S 56.29501° W; 0.5 m deep; 04
March 2017; 21:00; Jeremy K Dickens leg.; Lake
Outlet; Dipnet; Formalin; CZPLT-I 0127.
Sternopygus macrurus (Bloch & Schneider 1801)
(Fig. 7g)
The most common knifefish in the lake, this
species is widely distributed throughout South
America east of the Andes (Reis et al. 2003) and
easily identified by the dark humeral spot posterior
to the branchial opening. A crepuscular insecti-
vore, it was often encountered in the shallows, es-
pecially at night, as well as in emergent vegetation
surrounding the lake. Sometimes captured in gill
nets but not sought after by fishermen.
Material: • 1 adult; Laguna Blanca; 25 April
2014; PLT exped.; night fishing with spotlight and
dipnet; CZPLT-I 0089 • 1 adult; Laguna Blanca,
N Shore; 23.80825° S 56.28516° W; 28 June
2016; PLT exped.; Gillnet; Formol, tissue collected
(pectoral fin); CZPLT-I 0033 • 2 adults; Laguna
Blanca, Outlet; -23.81288°; -56.29501°; 0.5 m
deep; 04 March 2017; 21:00; Jeremy K. Dickens
leg.; Lake Outlet; Dipnet; Formalin; tissue collect-
ed (right pectoral fin); CZPLT-I 0125/0126 • 1
adult; Second beach; 14 February 2013; PLT ex-
ped.; CZPLT-I 0020.
Perciformes
Cichlidae
Cichlasoma dimerus (Heckel 1840) (Fig. 8a)
Identified by the black dot surrounded by a pale
ring in upper half of caudal fin base, dark posterior
marking on each scale, scales in posterior portion
of dorsal and caudal fins and three dorsal fin spines
(Almirón et al. 2015). It is distributed throughout
the Paraguay and Lower Paraná basins where its ag-
gressive nature, parental care and generalist omniv-
orous feeding habitats enable it to outcompete less
abundant species in closed lentic systems. At Lagu-
na Blanca it was one of only two species present in
the seasonal forest pond, were it occurred at very
high density. It was less common in the lake, where
it was mostly found in the marshy shallows but also
in deeper water amongst the emergent vegetation.
At night they were observed sleeping in very shal-
low water (< 10 cm), most likely to avoid preda-
tors.
Material: • 1 adult; First beach; 17 February
2013; PLT exped.; CZPLT-I 0022 • 1 ind.; Laguna
Blanca, Outlet stream; 12 April 2014; PLT exped.;
Lake Outlet Stream; CZPLT-I 0072 • 1 adult; La-
guna Blanca, Outlet; 23.81327° S 56.29482° W;
05 August 2016; Jeremy K Dickens leg.; dipnet;
formalin; tissue collected (left pelvic fin); CZPLT-
I 0049/0051 • 1 adult; Laguna Blanca, Outlet;
23.81331° S 56.29480° W; 0.5 m deep; 09 August
2016; night; Paul Smith leg.; Lake outlet, edge of
marsh; dipnet; EtOH; sleeping in shallows, kept &
died in captivity about 1 month after; CZPLT-I
0099 • 1 immature; Laguna Blanca, Outlet;
23.81288° S 56.29501° W; 0.5 m deep; 04 March
2017; 21:00; Jeremy K. Dickens leg.; Lake outlet,
edge of marsh; dipnet; formalin; Sleeping in shal-
lows; CZPLT-I 0133 • 1 ind.; same as preceding;
EtOH; CZPLT-I 0652 • 9 Juveniles; Rancho Lagu-
na Blanca, Seasonal Pond; 23.81716° S 56.29035°
W; 0.1 m deep; 15 February 2017; 21:00; Jeremy
K Dickens leg.; Seasonal Pond in Atlantic Forest;
dipnet; EtOH; Sleeping in shallows CZPLT-I 0104
• 1 Adult; Rancho Laguna Blanca, Seasonal Pond;
-23.81716° S 56.290354° W; 0.2 m deep; 27 Feb-
ruary 2017; 20:40; Jeremy K. Dickens leg.; Season-
al Pond in Atlantic Forest; dipnet; formalin; Sleep-
ing in shallows; CZPLT-I 0121 • 1 Subadult; same
as preceding; CZPLT-I 0122 • 5 Juveniles; same as
preceding; CZPLT-I 0123 • 10 Juveniles; same as
preceding; CZPLT-I 0124 • 1 ind.; Southern cor-
ner of Laguna Blanca; 23.81529° S 56.29218° W;
14 July 2016; PLT exped.; gillnet; formalin, tissue
collected (pelvic fin); CZPLT-I 0039 • 1 subadult;
Stream, near bridge; 11 February 2013; PLT ex-
ped.; CZPLT-I 0003.
Laetacara dorsigera (Heckel 1840) (Fig. 8b)
Diagnosed by the dark patch in mid dorsal fin
and cycloid scales on head. It occurs in the
Paraguay and Lower Paraná basins as well as the
Guaporé River (Reis et al. 2003; Vera-Alcaraz et al.
2017). It was less common than C. dimerus in the
lake and was only collected around the lake outlet.
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169
Jeremy Kenneth Dickens
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 169
aqua vol. 25 no. 4 - 15 October 2019 170
Annotated checklist to the fish of Laguna Blanca, San Pedro, Paraguay
Figs 7a-g. Cyprinodontiformes and Gymnotiformes of Laguna Blanca. a) Phallotorynus psittakos, b-c) Melanorivulus puncta-
tus, d) Neofundulus cf. paraguayensis, e) Gymnotus carapo australis, f) Eigenmannia aff. trilineata, g) Sternopygus macrurus.
Material: • 1 Juvenile; Laguna Blanca; 14 April
2014; PLT exped.; CZPLT-I 0077 • 1 adult; Lagu-
na Blanca, Outlet; 23.81327° 56.29482° S W; 05
August 2016; Jeremy K. Dickens leg.; dipnet; For-
malin; tissue collected (eft pelvic fin); CZPLT-I
0050 • 3 adults; Laguna Blanca, stream by bridge;
08 April 2014; PLT exped.; Lake Outlet Stream;
N/A; CZPLT-I 0068.
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 170
Crenicichla lepidota Heckel 1840 (Fig. 8c)
Diagnosed by dark humeral spot above pectoral
fin, c. 38 scales in longitudinal series (c. 38) and xvi-
ii.13 dorsal-fin rays. Distributed in the Paraguay,
Lower Paraná, Uruguay, Guaporé and coastal
drainages of Rio Grande do Sul (Lucena & Kullan-
der 1992) this species was common throughout the
lake, including in much deeper water than other Ci-
chlidae. Given its piscivorous nature it was frequent-
ly caught with baited hooks as well as in gillnets and
was sometimes taken (but not sought after) by fish-
erman.
Number: • 1 indiv; Laguna Blanca, Outlet
stream; 15 April 2014; PLT exped.; Lake Outlet
Stream; CZPLT-I 0078 • 1 Juvenile; Laguna Blan-
ca, Outlet; -23.81327° S -56.29482° W; 05 August
2016; Jeremy K. Dickens leg.; dipnet; Formalin;
tissue collected (left pectoral fin); Several faint ver-
tical bands evident, caudal fin red with 3 crescent-
shaped rows of dark spots on middle rays and dark
basal spot; CZPLT-I 0052 • 1 Juvenile; Laguna
Blanca, Outlet; 23.81276° S 56.29537° W; 0.5 m
deep; 14 February 2017; 18:00; Jeremy K. Dickens
leg.; Lake Outlet Stream, under overhanging vege-
tation; seine net; formalin; CZPLT-I 0100 • 2 ind.;
Stream, near bridge; 11 February 2013; PLT ex-
ped.; CZPLT-I 0005/0006.
Siluriformes
Auchenipteridae
Tatia neivai (Ihering 1930) (Fig. 8d)
This little catfish was diagnosed by the pattern of
scattered white dots across the body and dark ver-
tical bars in the caudal fin (Sarmento-Soares &
Martins-Pinheiro 2008). Typical of headwaters of
the Paraguay and Upper Paraná (Sarmento-Soares
& Martins-Pinheiro 2008), they were only found
in the lake outlet at night. Shoals of around half a
dozen individuals would gather here were they
would retain the same position on the water's sur-
face by swimming into the current, intermittently
sweeping out at passing food.
Material: • 3 adults; Laguna Blanca; 25 April
2014; PLT exped.; night fishing with spotlight and
dipnet; CZPLT-I 0086 • 3 adults; Laguna Blanca,
Outlet Stream; 23.81288° S 56.29509° W; 02 Au-
gust 2016; Jeremy K Dickens leg.; small clearwater
stream; Dipnet; formol; tissue collected (left pelvic
fin); In school of around a dozen individuals; CZ-
PLT-I 0043 to 0045 • 2; Adult & Juvenile; Laguna
Blanca, Outlet; 23.81288° S 56.29501° W; 0.5 m
deep; 04 March 2017; 21:00; Jeremy K. Dickens
leg.; Lake Outlet Stream; Dipnet; formalin; hover-
ing mid-current at water’s surface; CZPLT-I 0134.
Trachelyopterus aff. coriaceus Valenciennes 1840
(Fig. 8e)
T. coriaceus is found throughout the coastal
drainages of the Guianas and Brazil as well as in the
Amazon basin (Ferraris Jr. 2007; Reis et al. 2003).
Morphologically very similar records from the Up-
per Paraguay basin, in Brazil (Britski et al. 2009)
appear to be an unnamed species. Neris et al.
(2010) also found a similar looking specimen in
the Manduvirá River, Cordillera department. The
absence of an adipose fin rules out T. galeatus and
T. striatulus - the only species of driftwood catfish
proven to occur in Paraguay (Koerber et al. 2017).
It was often caught as bycatch in gill nets in the
emergent vegetation.
Material: • 1 ind.; Laguna Blanca, N Shore;
23.80825° S 56.28516° W; 28 June 2016; PLT ex-
ped.; gillnet; formalin, tissue collected (pectoral
fin); CZPLT-I 0034 • 1 ind.; R2 Rightside, 25
March 2013; PLT exped.; CZPLT-I 0029 • 1 ind.;
Laguna Blanca, Second cove; 22 April 2014; PLT
exped.; small gillnet CZPLT-I 0082.
Callichthyidae
Callichthys callichthys (Linneaus 1758) (Fig. 8f)
Identified by the rounded tail, absence of cora-
coid bones in the thoracic region and two rows of
bony plates, this armoured catfish is typical of tem-
porary waterbodies and is widespread in South
America east of the Andes and north of Buenos
Aires. It is able to move over land due to its air-
breathing ability and modified pectoral fins. A sin-
gle specimen was captured in a small pool (1x1.5m
x 0.5m deep) in the flooded Cerrado.
Material: • 1 adult; Rancho Laguna Blanca;
23.77695° S 56.29134° W; 17 September 2016;
Jeremy K. Dickens leg.; Small Pool (1x1.5m x
0.5m deep) in temporarily flooded Cerrado; dip-
net; EtOH; CZPLT-I 0059.
Heptapteridae
Rhamdia quelen (Quoy & Gaimard 1824) (Fig. 8g)
The widely distributed ‘South American Catfish’
is distinguished by its long adipose fin that is con-
nected to the body along its entire base and sube-
qual emarginated caudal fin. A carnivore, it was
sometimes caught in gillnets or baited hooks but
was not sought after by fishermen.
Material: • 1 adult; Laguna Blanca; 09 July 2016;
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171
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PLT exped.; CZPLT-I 0091 • 1 adult; Laguna
Blanca, N Shore; 23.80825° S 56.28516° W; 28
June 2016; PLT exped.; gillnet; formalin; tissue
collected (pectoral fin); CZPLT-I 0035.
Loricariidae
Rineloricaria aurata (Knaack 2003) (Fig. 8h)
Identified by four longitudinal rows of lateral
plate series, absence of mid-dorsal plates, the single
filament on the (upper) caudal fin as well as odon-
todes on the dorsum of the head and predorsal re-
gion in mature males (Figure 8g) (Vera Alcaraz et
al. 2012). Feeding on algae and detritus, this
species was most often found on the open sandy
bed in the outlet stream but also in the sandy shal-
lows along the beach. Their occurrence in sandy
areas differs somewhat from the cited association
with “leaves of partially submerged plants in small
streams” (Vera Alcaraz et al. 2012), although
submerged leaves were present a short distance
downstream. Only recently described, it is found
in the Paraguay and Guaporé rivers in Paraguay
and Brazil and was previously recorded in the Jejuí
River.
Material: • 1 adult; 2nd Beach 10m off shore; 10
May 2012; PLT exped.; CZPLT-I 0002 • 1 adult;
beach shore, 12 February 2013; PLT exped.; CZ-
PLT-I 0004 • 1 adult; Laguna Blanca, Outlet
Stream; 23.81288° S 56.29509° W; 02 August
2016; Jeremy K. Dickens; flat sandy bed in small
clearwater stream (slow flowing); dipnet; formalin;
tissue collected (left pelvic fin); only single dorsal
filament on caudal fin (no ventral) seen in various
others individuals not collected CZPLT-I 0046 • 1
adult; Laguna Blanca, Stream by bridge, 14 April
2014; PLT exped.; Lake Outlet Stream; CZPLT-I
0073.
Synbranchiformes
Synbranchidae
Synbranchus marmoratus Bloch 1795 (Fig. 8i)
Unmistakable, the widespread ‘swamp eel’ was
found in the vegetation of the marshy lakeshore
and lake outlet.
Material: • 1 Juvenile; Laguna Blanca; 25 April
2014; PLT exped.; night fishing with spotlight and
dipnet; CZPLT-I 0088. • 1 Adult; same locality;
Mar-2014; same collector(s); caught by fisherman
near reedbed; CZPLT-I 0031. • 1 Juvenile; Lake
Shore Beach; 22 June 2012; same collector(s); CZ-
PLT-I 0001. • 1 Juvenile; Outlet, Laguna Blanca;
23.81311° S 56.29480° W; 0.5 m deep;14 Febru-
ary 2017,18h00; Jeremy K. Dickens; edge of
marsh; seine net; formalin; CZPLT-I 0101. • 1 Ju-
venile; Outlet, Laguna Blanca; 23.81337° S-
56.29480° W; 0.2m deep;14 February 2017;
18h00:00; Jeremy K. Dickens leg.; Marshy
Lakeshore; Seine net; EtOH; CZPLT-I 0102. • 1
Juvenile; Outlet, Laguna Blanca; 23.81311° S
56.29480° W; 0.5 m deep;14 February 2017;
18:00:00; Jeremy K. Dickens; Lake Outlet, edge of
marsh; Seine net; Formalin; CZPLT-I 0120.
DISCUSSION
The fish species richness of Laguna Blanca is con-
sistent with other Neotropical lentic systems
(Granado-Lorencio et al. 2012; Iwaszkiw et al.
2010; Petry et al. 2010; Valdiviezo-Rivera et al.
2018). This is generally lower than for lotic systems
due to the lower levels of habitat heterogeneity and
greater environmental stability (Lowe-McConnell
1987). The distribution of species richness also fol-
lowed that for artificial Neotropical reservoirs, in-
creasing on a gradient from the lake centre to the
lakeshore and greater still in the outlet, in relation
to increasing habitat heterogeneity and temporal
fluctuations (Agostinho et al. 2016). Agostinho et
al. (2016) also argued that the lack of native species
pre-adapted to pelagic lentic environments was re-
sponsible for the low number of species in the
pelagic zone. Although the composition of species
follows that generally found in the Neotropics,
there is a notable scarcity of benthivorous species,
particularly the Curimatidae and Anostomidae,
with only a handful of specimens of only two
species, whereas they usually form the bulk of
catches in other lentic systems and are represented
by several species. This seems likely due to the olig-
otrophic nature of the lake, which limits algal
growth and reduces the build-up of organic sub-
strates that are needed to sustain large populations
of these species.
Nevertheless, the assemblage of species present
was unique with an undescribed species of Hemi-
grammus and first country record of Moenkhausia
bonita, as well as an unusual form of Bryconops aff.
melanurus. Lakes are well-known centres of en-
demism due to their isolation (Levêque et al. 2007)
and given that Laguna Blanca is the only lacustrine
system for hundreds of kilometres with large differ-
ences from the surrounding aquatic ecosystems,
the presence of previously unrecorded forms is to
be expected. Additionally, just under half the
species present had high conservation value. Four
aqua vol. 25 no. 4 - 15 October 2019 172
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 172
aqua vol. 25 no. 4 - 15 October 2019
173
Jeremy Kenneth Dickens
Figs 8a-i. Perciformes, Siluriformes and Synbranchiformes of Laguna Blanca: a) Cichlasoma dimerus, b) Laetacara dorisigera,
c) Crenicichla lepidota (juvenile), d) Tatia neivai, e) Trachelyopterus aff. coriaceus, f) Callichthys callichthys,g) Rhamdia quelen,
h) Rineloricaria aurata, i) Synbranchus marmoratus (juvenile).
AQUA 25-4.qxp_AQUA 25/10/19 15:01 Pagina 173
species (12.5 %) are endemic to the Paraguay Riv-
er, of which Phallotorynus psittakos is only known
from Paraguay. Four more (12.5 %) were restricted
to the Paraná-Paraguay. Six more species and one
subspecies (22 %) are restricted to the De La Plata
basin, bringing the total number of species endem-
ic to the greater De La Plata system to 15 (47 %),
with five more extending only slightly further into
the Guaporé, Mamoré and/ or drainages of south-
ern Brazil. Another two species, Brycon hilarii and
Salminus brasiliensis, are potamodromous.
Despite its uniqueness and regional importance,
Laguna Blanca is facing a growing number of
threats. Located in a prime agricultural zone, the il-
legal deforestation (often through burning) of the
remaining forest around the lake is increasing the
amount of pollutants entering the lake through
runoff, including agrochemicals from nearby soy
fields. However, of particular concern, is the threat
of habitat destruction to Rancho Laguna Blanca,
formerly “Reserva Natural Laguna Blanca”, which
borders over half the lake, but which has been
without formal protection status since February
2015. It is currently for sale and may soon be con-
verted to agriculture with negative consequences to
the lake. The uncontrolled development of tourist
facilities in the immediate vicinity of the lake, in-
cluding modifications to the lakeshore and dump-
ing of organic waste into the lake, have also already
caused notable increases in turbidity and eutrophi-
cation, especially during summer (pers. obs.). If this
continues, the reduction in water quality could be
disastrous to the persistence of more sensitive
species adapted to oligotrophic conditions and
would also negatively impact the local human
community who are directly reliant on the lake for
water.
Unregulated fishing also threatens the stability of
the fish community as healthy populations of the
dominant predatory species are required to main-
tain the unique diversity of prey species (Mittel-
bach et al. 1995). Their depletion can result in the
extinction of less abundant or sensitive prey species
due to the increased competition from more ag-
gressive species (Petry et al. 2010). By far the most
dominant predators in the littoral zone are H. ma -
la baricus and S. maculatus. Although we have no
measure to determine the population health of
these keystone species, the small size and isolation
of the lake make them highly susceptible to over-
fishing, potentially threatening the balance of the
ecosystem and survival of more sensitive species.
On the other hand, the small populations of large
characids (Brycon hilarii and Salminus brasiliensis)
in the pelagic zone are only sustained by the immi-
gration of individuals to the lake during high water
events so are a sink population with a net negative
turnover of individuals. Local fisherman also recall
catching ‘Surubi rayada’ (or Pseudoplatystoma reti -
culatum) in the lake, which would likely also be an
immigrant species, but this cannot be proven. Fi-
nally, the raising of Tilapia (Oreochromis sp.) within
a hundred meters of the shoreline poses a serious
risk of invasion to the lake.
To safe-guard this unique heritage the following
actions are recommended: (1) enforcement of fish-
ery regulations (2) strict regulation of develop-
ments in the immediate vicinity of the lake, (3)
precautions to prevent species introductions from
aquaculture (such as the use of sterile hybrids), (4)
enforcement of the national laws restricting defor-
estation of forest remnants and (5) regulating of
the use of agrochemicals in the surrounding area. A
prime focus for biodiversity and water-resource
protection should be the awarding of permanent
protection status for Rancho Laguna Blanca.
ACKNOWLEDGEMENTS
The author is grateful to Fundación Para La Tier-
ra for the support in putting together this work, to
the interns and volunteers who carried out much
of the earlier fieldwork, notably Sean Gee (2013),
Keith Palke (2014), Samuel Morel and Harry
Stephens (2016). To Luiz A. W. P Peixoto, Priscila
Camelier, Carlos A. de Lucena, F. Lima, D. Nielsen
and Marcos Mirande for assistance in identifica-
tion, Jorge Ayala for extensive local knowledge and
Brogan Pett for re-taking several specimen photos.
Collection permits were obtained from the Secre-
taria del Medio Ambiente (SEAM).
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