Revista de Biología Tropical, ISSN: 2215-2075, Vol. 73: e20252701, enero-diciembre 2025 (Publicado Nov. 04, 2025)

Biology of an introduced species of Pleco fish (Siluriformes: Loricariidae)

in a tropical freshwater ecosystem

Alexandre Tisseaux-Navarro1*; https://orcid.org/0000-0003-2634-2036

1. Universidad Nacional, Department of Physics, Heredia, 86-3000, Costa Rica; alexandre.tisseaux.navarro@una.cr

(*Correspondence)

Received 14-XII-2024. Corrected 19-V-2025. Accepted 02-X-2025.

ABSTRACT

Introduction: Loricariid species have been introduced in many countries in the world, causing negative ecosys-

tem effects wherever they invade. Species from this family, also known as Pleco, have been recorded from Lake

Nicaragua for several years.

Objective: investigate basic aspects of the biology of Pleco in Lake Nicaragua, as an initial step to generating

information to contribute to establishing management strategies for this species.

Methods: We assessed relative abundance and relative weight, Gonadosomatic index (GSI), Capture optimiza-

tion Index, Catch composition by Net type, and environmental variables.

Results: 23 different species were captured, with the Pleco being the species represented in the greatest number

of individuals and weight. Mature ovaries were observed throughout the year, except in July, GSI values were

always high between September and June. High number of females were capture in September and October, as

well as the period between March and May. The highest values of the capture optimization index were obtained

in September and October. Additionally, the loricariids tended to prefer sites and times where water levels were

deepest, potentially as a response to increased Río Frio’s flow. This aligns with the strategy of conserving energy

by seeking areas of reduced water current.

Conclusions: In the Southeast of Lake Nicaragua, increases in Pleco (Hypostomus sp.) populations have been

matched corresponding declines in the capture of species of commercial interest. As a result, switching to target

the Pleco in the area could provide an opportunity for local fishers to extract an abundant resource and avoid the

extraction of local species, as long as viable markets are developed for Pleco.

Key words: invasive species, Loricariidae, Nicaragua, Gonadosomatic index, fishing.

RESUMEN

Biología de una especie introducida del pez Pleco (Siluriformes: Loricariidae)

en un ecosistema de agua dulce tropical

Introducción: En todo el mundo, las especies de loricáridos introducidas han tenido un impacto negativo en los

ecosistemas invadidos.

Objetivo: explorar la biología básica del Pleco (Hypostomus sp.) en el sureste del lago de Nicaragua como un

primer paso para establecer estrategias de manejo.

Metodología: Evaluamos la abundancia, el peso, el índice gonadosomático (IGS), índice de optimización de la

captura, la selectividad de las redes y factores ambientales.

Resultados: Capturamos 23 especies, siendo el Pleco el más común. Se observaron ovarios maduros durante todo

el año, excepto en julio; los valores del IGS fueron constantemente altos entre septiembre y junio. Se capturaron

muchas hembras en septiembre, octubre y de marzo a mayo. Los valores más altos de optimización de captura se

https://doi.org/10.15517/mhtgnw19

AQUATIC ECOLGY

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INTRODUCTION

Until a recently, documented cases of inva-

sive fish species around the world were con-

fined to particular areas, since natural barriers

were sufficient to prevent widespread disper-

sion. However, recently the introduction of

non-native species into new ecosystems has

become more frequent due to a range of anthro-

pogenic causes (Lowe et al., 2000). Invasive

species do not just challenge the conservation

of biological diversity but can generate substan-

tial additional ecological impacts (Gallardo et

al., 2015; Simberloff et al., 2013). In fact, their

impacts have the potential to become a major

cause of extinction of fish around the world

(Clavero & Garcia-Berthou, 2005).

In Nicaragua, the biology of introduced

fish species, and their impact on ecosystems,

has received little study. However, tilapia (Oreo-

chromis spp.) were introduced into Lake of

Nicaragua at least 35 years ago (McKaye et

al., 1995) and recently been followed by the

introduction of “Pleco”. Pleco, belongs to the

Loricariidae (Nelson, 2006). They are frequent-

ly displayed in aquariums (Krishnakumar et

al., 2009), and it is believed that release by

aquarists, or accidentally escape, has led to

invasions in inland waters around the world

(Mendoza et al., 2008).

Loricariids often have negative ecosys-

tem effects; their armoured bodies and strong

spines on the fins mean that few native species

can feed on them (Armbruster & Page, 2006;

Karunarathna et al., 2008; Nico, 2010; Ríos-

Muñoz, 2015) leading to their hyper-abundant

and the exclusion of native fish from their tra-

ditional niches. Ecosystem effects range from

competition for resources (food and space),

predation of eggs and larvae, alteration to the

environment (erosion on the banks), and other

harmful interactions, such as birds drowning

when try to consume a Pleco (Bunkley-Wil-

liams et al., 1994; Gibbs et al., 2010; Karunara-

thna et al., 2008; Kolar et al., 2010; Nico et al.,

2009). In addition, those captured by commer-

cial fishers are typically released because they

usually do not have commercial value, further

accelerating population growth.

Introduction of a loricariid (Pterygophlic-

thys spp.) into the Infiernillo dam, Mexico, saw

the decline of one of the most important fresh-

water fisheries in Mexico, with a progressive

reduction in the capture of marketable species

until Pterygophlicthys spp. Came to represent

almost all of the catch by local fishers, leading to

fishing becoming economically unfeasible. This

left 3 600 fishers out of work and flowed on to

impact a total of 46 000 people, including fish

processors and the families of those depending

on the fishing industry (Mendoza et al., 2008).

Consequently, there are serious concerns about

the damage that Pleco may be causing to the

fisheries production and livelihoods of those

depending on fishing in Lake Nicaragua. The

risk is substantial. In the town of San Carlos, to

the Southeast of Lake Nicaragua, employment

options focus on livestock and agricultural

activities, and in general these opportunities

are scarce, so many turn to artisanal fishing

as the main source of family income (Gadea,

2003). Reports from artisanal fishers in the area

indicate that Pleco are already causing serious

problems because of damage to nets, and many

associate the appearance of Pleco with decreas-

es of species of commercial interest (Härer et

al., 2017; Maradiaga, 2009).

Artisanal fishing is critical to Nicaragua.

In 2016, there were about 1 407 artisanal fish-

ers in Nicaraguan inland waters registered with

obtuvieron en septiembre y octubre. Los loricáridos preferían sitios y momentos con mayor profundidad, posi-

blemente debido al aumento del caudal del Río Frío.

Conclusiones: En el sureste del Lago de Nicaragua, el incremento de las poblaciones de Pleco ha coincidido con la

disminución de especies de interés comercial. Enfocarse en la captura del Pleco podría beneficiar a los pescadores

locales y preservar especies locales.

Palabras clave: especie invasora, Loricariidae, Nicaragua, índice gonadosomático, pesca.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 73: e20252701, enero-diciembre 2025 (Publicado Nov. 04, 2025)

(Instituto Nicaragüense de la Pesca y Acuicul-

tura [INPESCA], 2018). This gives an idea of

the number of families that depend on fishing

in these systems. Added to this are many fishers

who do not register with INPESCA, and people

who fish for self-consumption. Indeed, given

that Lake Nicaragua (including the San Juan

River) is not only the largest freshwater system

in Nicaragua but the largest in Central Ameri-

ca, coupled with the current difficult economic

situation in Nicaragua, means that a large part

of the populations around the coast of the lake

rely on fishing-related activities for survival.

Detailed knowledge of the fisheries biology

of Pleco is a vital basis for the establishment

of effective measures to manage this invasive

species. Consequently, we investigated basic

aspects of the biology of Pleco in Lake Nicara-

gua as an initial step to generating information

to support the establishment of management

strategies for the loricariids introduced in

Lake Nicaragua. In particular, we assessed (a)

relative abundance and relative weight, (b)

Gonadosomatic index (GSI), (c) Capture opti-

mization Index (COI), (d) Catch composition

by Net type, and (e) environmental variables.

MATERIALS AND METHODS

Study area: The study area is located

Southeast of Lake Nicaragua (11°7’00” N &

84°47’00” W), in the Department of Río San

Juan. Sampling was conducted monthly for one

year at two locations (Fig. 1). Site A is located

500 m from the coastline of the lake, where

local fishers regularly set their nets. Site B is

located near the coast (150 m offshore), an area

not commonly used by artisanal fishers.

Fish capture: Fish were collected between

July 2017 to June 2018 using a combination of

three methods: mesh nets, traps and cast nets.

A set of mesh nets (Table 1), together with

a fish trap, were deployed simultaneously at

both locations, on two nights per month, for

approximately twelve and a half hours (from

Table 1

Measures of gillnets used for catching fish in two sites Southeast of Lake Nicaragua between July 2017 and June 2018.

Net identification Mesh size (in) Length (m) Height (m) Yarn thickness Legality

Net 1 2 17 1.2 0.4 Illegal

Net 2 4 33 1.2 0.4 Legal

Net 3 4.5 40 1.2 0.2 Illegal

Fig. 1. Location of sampling sites. (Source: adapted from Sierra, 2012).

4Revista de Biología Tropical, ISSN: 2215-2075 Vol. 73: e20252701, enero-diciembre 2025 (Publicado Nov. 04, 2025)

4:45 pm to 5:15 am). The nets were anchored

so they remained near the bottom. The same

number of cast net samples were collected at

the two sites. Organisms were identified to the

lowest possible taxonomic level with the help

of taxonomic keys and literature (Armbruster,

2004; Armbruster et al., 2015; Bussing, 2002;

Hoover et al., 2004); organisms not belonging

to the Loricariidae family were released. The

species from Loricariidae family found in this

drainage have been identified by Dr. Jona-

than Armbruster (Matamoros et al., 2016) as

Hypostomus cf. niceforoi. In the current study

we only found one species of loricariid, so we

prudently decided to use Hypostomus sp. to

refer to the species.

Relative abundance and relative weight:

The number of specimens per species was

counted and the total weight (TW) of all the

fish measured using an American Weight Scales

digital scale model AWS-600-BLK, with an

accuracy of 0.1 g. In addition, the total lengths

(TL) of the Pleco were with a 0.5 mm preci-

sion ichthyometer. In this way it was possible

to estimate monthly from the catches per unit

of effort (CPUE), the relative abundance (RA

%) and the relative weight (RW %) of the Pleco

and the rest of the species captured. Relative

abundance was determined by the following

formula:

Relative weight was determined by the fol-

lowing formula:

Reproductive parameters: Gonads were

extracted from each Pleco, sex was deter-

mined by macroscopic observation, and the

proportion of males and females was calcu-

lated. The gonads of each female were weighed

with an American Weigh Scales digital scale,

model AWS-600-BLK, with an accuracy of

0.1 g. Gonadosomatic index (GSI) was cal-

culated for each fish individually using the

following formula:

Where: GSI is Gonadosomatic index, GW

is gonad weight, TW is fish total weight.

Subsequently, the GSI values grouped

monthly were compared through a Dunn test

with the R program (R Core Team, 2018), to

assess changes in average GSI over time.

Capture optimization Index: Three vari-

ables were considered in formulating a recom-

mendation on the sampling time that would

maximize Pleco capture success: (i) GSI, since

the higher its value the greater the number of

eggs and offspring, (ii) the number of females

per male, since if few females are captured even

if the GSI is high the total number of eggs will

be low, so it is desired to capture large numbers

of females and, (iii) the relative abundance

of Pleco was assessed, in order to determine

when Pleco captures could be maximized while

minimizing the catch of native fish. An index

was formulated to unite the three variables of

interest. First, the value of these three variables

in each month was normalized with the follow-

ing formula:

Where: zi is normalized value of the vari-

able in the month i, xi is value of the variable in

the month i, min(x) and max(x) represent the

minimum and maximum value of the variable

across the entire year.

Once the variables were normalized the

capture optimization index was obtained using

the following formula:

Where: COIi is value of the optimization

capture index in the month i, NGSi is normal-

ized GSI value in the month i, NARi is nor-

malized value of the relative abundance in the

month i for the site with greater abundance,

NHMi is normalized value of the number of

females per male in the month i.

Catch composition by Net type: to deter-

mine which net would capture more Pleco and

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fewer native fish, data were standardized to

provide an estimate of weight relative to each

net being 100 meters long, and a new relative

weight was estimated for each of the nets used.

Each native fish was classified as legal or illegal,

legal catch refers to fish longer than minimum

size established by INPESCA in continental

waters Ministerio del Ambiente y los Recur-

sos Naturales (MARENA) y el Instituto Nica-

ragüense de la Pesca y Acuicultura (INPESCA,

2013), regardless of the net where it was caught

was legal or not (Table 1).

Environmental variables: The surface

temperature and depth were recorded from a

Garmin model Striker 4 echosounder, equipped

with a CHIRP transducer (77/200 kHz). This

was done every time the nets were placed and

collected at various points along the net set

and used to calculate average temperature and

depth for each site per month.

Data analysis: A Kruskal-Wallis test was

performed to compare the relative abundance

and relative weight of fish between the two

sampling sites. Gonadosomatic index values

grouped by month were also compared with a

Kruskal-Wallis test. Kruskal-Wallis tests were

also performed to compare the normalized

relative weight of native fish and Pleco between

the three nets used. In addition, the rela-

tionships between the relative abundance at

each site and the environmental variables were

assessed using Spearman rank correlations.

Analyzes were carried out using R software (R

core team, 2018).

RESULTS

Relative abundance and relative weight:

A total of 1 881 organisms were captured, from

23 different species belonging to 10 families,

with Cichlidae being the most common fam-

ily. The species represented by the greatest

number of individuals was the Pleco, Hypos-

tomus sp. (618 organisms), followed by the

cichlid Amphilophus citrinellus (552 organisms)

(Fig. 2).

There were significant differences (p <

0.05) in the relative abundance (RA) of Hypos-

tomus sp. at both sites. The RA of this species at

Fig. 2. Relative monthly abundance (between July 2017 and June 2018) of the species with the highest number of catches at

the two sampling sites (Site A: continuous line, Site B: dashed line) in the Southeast of Lake Nicaragua.

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the site near the coast (Site B) was significantly

greater than at the site far from the coast (Site

A) (Fig. 2). Amphilophus citrinellus occurred in

the higher RA than Hypostomus sp. at Site A but

the pattern was reversed at Site B. The relative

abundance of the Pleco was high at Site B from

September to April, with the highest values in

September, October and November. The abun-

dance of Pleco was very low at Site A, with none

captured in several months and no more than 5

specimens were captured in a single month. At

site B, at least 7 Pleco were captured per month,

and more than 50 were caught in 8 of the 12

months sampled.

The relative weight (RW) of Pleco was

high at site B (near the coast) and only failed to

exceed 50 % of the total weight captured at the

site in June (Fig. 3). From August to April RW

varied between 78 and 94 %, with the highest

values in September, October and November.

There were significant differences in the RW of

Pleco between the two sites (p < 0.05), with the

RW at site A (far to the coast) lower in every

month. At this site Amphilophus citrinellus had

the highest RW over most of the year.

Reproductive parameters: Mature ovaries

were observed throughout the year, except in

July, and it was in this month that the low-

est average value of GSI was obtained, while

the highest values were obtained in May and

June. Despite this, GSI values were always high

between September and June (Fig. 4). Only

significant differences were found between the

values in July and those in December, January,

March, April, and May.

The number of females and males varied

according to the month (Table 2); from Septem-

ber to May more than 20 females were captured

per month, but not in the months of June, July

and August. The number of females for each

male changed over the sampling year, high in

September and October, as well as between

March and May.

Capture optimization index: Due to low

abundance of Pleco in site A, only site B values

Fig. 3. Monthly relative weight (between July 2017 and June 2018) of the species with the highest number of catches at the

two sampling sites (Site A: continuous line, Site B: dashed line) in the Southeast of Lake Nicaragua.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 73: e20252701, enero-diciembre 2025 (Publicado Nov. 04, 2025)

were considered for this analysis. The highest

values of the capture optimization index were

obtained in September and October. In addi-

tion, in November, March, April and May the

value of the COI be high (greater than 0.67).

The rest of the months the COI was low, less

than 0.6, especially in June, July, and August

(Table 2).

Catch composition by Net type: The per-

centage of legal catch was significative higher in

Net 2 (Fig. 5A), and all the catch by Net 2 in site

Fig. 4. Monthly average of the gonadosomatic index (GSI) of females of Hypostomus sp. captured between July 2017 and June

2018. Error bars represent the lower and upper percentiles (95 %). The letters represent the Dunn test result for comparison

of means. Months that share one or both letters do not show significant differences from each other in the value of the GSI.

Table 2

Number of females, number of males and male:female ratio captured per month and Capture optimization index (COI) of

Hypostomus sp. between July 2017 and June 2018 in the Southeast of Lake Nicaragua.

Month N females N males Male: female COI

July 12 21 1:0.57 0.12

August 13 20 1:0.65 0.23

September 43 16 1:2.69 0.90

October 42 17 1:2.47 0.92

November 38 29 1:1.31 0.68

December 39 26 1:1.50 0.57

January 39 35 1:1.11 0.55

February 25 31 1:0.81 0.38

March 51 28 1:1.82 0.68

April 34 18 1:1.89 0.69

May 23 10 1:2.30 0.74

June 2 5 1:0.40 0.07

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B was legal in almost every month sampled. Net

3 also captured a high percentage of legal fish.

In addition, the relative weight of Pleco was

significantly higher in Net 2 and Net 3 than Net

1, and high in Net 2 in site B (Fig. 5B).

Environmental variables: The surface

temperature (Fig. 6) showed similar behaviors

at both sites, however, there were differences

between months. The temperature was low

in July, rose from August to November, and

decreased again between December and Feb-

ruary, with lowest values in January. Between

March and June, it was very high, with May hav-

ing the highest temperature of the whole year.

Fig. 6 shows the distribution of tempera-

ture and water level in the two locations stud-

ied. Although the temperature was similar at

both sites, water levels varied between them.

The loricariids tended to prefer sites and at

times where water level was deepest, with a pos-

itive relationship between abundance and water

depth (rs = 0.93, p < 0.05). No relationship was

found between the abundance of this species

and surface temperature (rs = -0.25, p > 0.05).

DISCUSSION

Currently, it is likely that artisanal fishers

avoid catching Pleco due to the time required to

remove them from nets, the damage they cause

to the gear, and their lack of commercial value

fishers. When a non-native fish has little or no

socioeconomic value, it can acquire the status

of a plague (Britton et al., 2011), this is certainly

true in the case of the Pleco in the Southeast of

Lake Nicaragua.

Pleco in Lake Nicaragua seems to have a

strong positive relationship with sites and times

of greater water depth (Fig. 2, Fig. 5). Víquez

(2017) used a cast net in a rapid evaluation of

six sites in the Northeast Caribbean Ramsar

Wetland in Costa Rica, which fluvially connects

with the Lake Nicaragua, and found loricariids

in only two sites, but in low abundances (8 %

and 19 %). However, since no gillnets were used

in that study, the relative abundance of loricari-

ids cannot be directly compared. Nonetheless,

both studies suggest that Pleco may favor spe-

cific habitats.

The abundance of species of the genus

Hypostomus has been linked to sites of greater

depth (Gerhard et al., 2004; Jayaratne & Sur-

asinghe, 2010; Mazzoni et al., 2009). Fialho et

al. (2008), on the Meia Ponte River in Brazil,

found a greater number of specimens of the

genus Hypostomus in periods when the water

level and temperature were highest. These

authors argue that changes in the abundance

of Hypostomus may be due to variations in the

Fig. 5. Boxplots of relative weight (between July 2017 and June 2018) of legal catch (at the left) and Pleco (at the right) at the

two sampling sites in the Southeast of Lake Nicaragua using three kinds of nets.

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environment, due to the increase in water speed

and volume. In Southern Lake Nicaragua this

could influence, with the increase of the flow

of Frío River (Fig. 1), the Pleco have to spend

more energy, so it may seek for nearby deep

areas in Lake Nicaragua where the water speed

and energy consumption is lower.

However, Hypostomus species do not

always show a preference for deep habitats.

Teresa & Casatti (2013), when evaluating two

species of this genus, found that they did not

show a clear preference for these types of envi-

ronments, and instead could opt for shallow

environments, suggesting that water velocity

could be significant factor in habitat selection.

Therefore, it is important that, in the case of the

species of the genus Hypostomus, evaluated in

Lake Nicaragua, there was found a positive cor-

relation with depth, and a greater abundance

during periods and at the site where the water

level was greater. In addition, it has been found

that some species of the genus Hypostomus

(Celestino et al., 2017) are more active during

the night and when the flow increases. These

data are of great importance for the effec-

tive control of Hypostomus in Lake Nicaragua,

since, as activity increases, they move more

and, therefore, make them more vulnerable to

encountering gill nets. This is likely the case in

the present work, where gillnets were used dur-

ing the night and large numbers of specimens

of the invasive species were captured.

Cook-Hildreth et al. (2016), observed that

in loricariids species the non-reproductive

period was less evident and shorter in the

introduced habitat than in their native habitat.

These authors argue that the photoperiod is

the main proximate factor in the reproduction

of these species, the non-reproductive period

(quiescence) being less and less evident in

places where the variation of the photoperiod

is less. This, integrated with what was observed

in this work (Fig. 4), could support the idea

that the quiescence period will decrease as

the photoperiod variation decreases, and that

in areas where the duration of the day is rela-

tively constant throughout the year, the quies-

cence period for these loricariid species may

not be evident.

Rueda-Jasso et al. (2013) found mature

gonads of Pterygoplichthys disjunctivus through-

out the year at the Infiernillo dam in Mexico.

Fig. 6. Surface temperature and average water level at two sites (A and B) in the Southeast of Lake Nicaragua measured with

a Garmin echosounder, from July 2017 to June 2018. The thick continuous line corresponds to surface temperature data in

degrees Celsius and the dashed line to water level in meters. The geometric figures differentiate from the sites.

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The authors argued that in the Infiernillo dam

the population of P. disjunctivus has found a

situation in which the lack of predators and a

surplus of food is conducive to an extended

reproductive period. Additionally, Gibbs et al.

(2017) showed that when P. disjunctivus is

introduced in a place where the environmental

conditions are stable and there is great avail-

ability of food, as the years progress, its period

of reproductive inactivity will become less and

less evident as in Florida (United States).

The results of GSI showed mature females

throughout the year in lake Nicaragua. This

may relate to the fact that Lake Nicaragua also

has stable conditions because it is in a tropical

zone, perhaps even more stable than in Florida

(Gibbs et al., 2017), with few variations in envi-

ronmental conditions during the year. There-

fore, is prudent to complement the GSI value

with more information to determine a period

in which capture efforts should be concentrated

in the area, such as the number of females that

are captured each month. This can help the

selection of a capture period that helps reduce

reproductive output. So, the months of Sep-

tember, October, March, and April, where we

have high values of GSI, as well as large num-

bers of females, would be important months

to concentrate capture and decrease the future

recruitment of the species. However, consid-

ering the months when the impact to native

species would be reduced, it seems that, based

on the COI number (Table 2), the best months

to concentrate catching efforts in Nicaragua,

would be the months with the highest rainfall:

September and October.

When making decisions for the manage-

ment of a non-native species, there are three

possible actions: (i) act quickly to find it, (ii)

eradicate it or (iii) control it (Britton et al.,

2011). In the case of Pleco in Nicaragua, the

first option is no longer viable because it has

been more than ten years since they were first

recorded. In terms of eradicating it, there are

few reported cases where this method has been

successful, and these are restricted to small and

closed water bodies and invariably requiring

substantial expenditure of funds (Britton et

al., 2011; Kolar et al., 2010). As a result of the

unviability of action (i) and the unlikelihood

of success from action (ii), control methods try

to minimize the impact and dispersion of the

invasive fish seems more viable in this case.

Selective removal is a common method

for managing invasive species, but finding gear

that effectively targets non-native fish without

harming native species remains challenging

(Britton et al., 2011; Kolar et al., 2010). Some

successful cases involve systems with few or

no native species, such as the use of gillnets to

control introduced trout in parts of the U.S. and

Canada (Knapp & Matthews, 1998; Parker et

al., 2001). In contrast, Lake Nicaragua supports

23 fish species, of which only Tilapia and Pleco

are non-native, increasing the risk of bycatch

and complicating selective removal.

Nevertheless, other studies suggest selec-

tive removal can work even in diverse sys-

tems. For instance, Lozano-Vilano et al. (2006)

eliminated an invasive African cichlid using

traps in the San José del Anteojo Well, Mexico.

Native species had declined dramatically, but

after removing the invasive, they were success-

fully reintroduced from nearby rivers. How-

ever, San José del Anteojo Well covers less than

1 km², whereas Lake Nicaragua spans 8 264

km² and contains numerous inflowing riv-

ers, making management far more complex in

scale and logistics.

Although this study was not designed to

compare fishing gear, gillnets used in deep

areas (Net 2) showed promising results, cap-

turing large numbers of adult Plecos (Fig. 5)

with limited bycatch and within legal mesh size

(MARENA & INPESCA, 2013). This aligns

with the findings of Wickramaratne et al.

(2020), who studied gillnet selectivity for P. d i s -

junctivus in Sri Lanka, concluding that smaller

mesh nets were ineffective for juveniles. In our

case, juveniles may occupy cryptic habitats like

burrows or submerged debris along lake and

river shores, making them less accessible to

nets. Gibbs et al. (2013) also observed this pat-

tern in Florida, linking it to predation pressure

on smaller individuals.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 73: e20252701, enero-diciembre 2025 (Publicado Nov. 04, 2025)

Catch composition by Net type in other

countries where introduced loricariids spe-

cies have been found, the approach has been

to encourage their consumption, and / or to

look for ways to take advantage of the spe-

cies. This is the case in Mexico, where it has

been used in the manufacture of meal for lamb

and tilapia feed, as well as possible use as a

crop fertilizer (Escalera-Gallardo et al., 2012;

Filigrana, 2016; Monares-Gallardo et al., 2012;

Tejeda-Arroyo et al., 2015).

In the Southeast of Lake Nicaragua, as well

as most fisheries worldwide, the introduction

of invasive species has resulted in substantial

declines in catches of species of commercial

interest. In the Southeast of this lake, species

such as Garfish (Atractosteus tropicus), Snook

(Centropomus spp.) and Rainbow Bass (Para-

chromis dovii), that were once of great com-

mercial importance and frequently caught by

fishers, are now rarely captured.

The biological findings of this study sug-

gest that Pleco in Lake Nicaragua reproduce

throughout the year, but with peaks of repro-

ductive activity and female abundance dur-

ing specific months, particularly September,

October, March, and April. This information

is key for designing targeted control strategies

aimed at reducing recruitment, especially if

capture efforts are aligned with the rainy season

(September-October), when impacts on native

species may also be minimized. While this

study did not aim to evaluate fishing gear effec-

tiveness per se, the observed success of legal

gillnets in deeper areas provides useful insights

into the feasibility of selective removal. As a

result, switching to target the loricariid species

in the area could provide an opportunity for

local fishers to extract an abundant resource

(Fig. 3) and avoid the extraction of local spe-

cies, as long as viable markets are developed.

This study provides a basis for local govern-

ments, and managers from countries in the

area to start establishing policies to control this

invasive species.

Ethical statement: The author declares

that he agrees with this publication; that there

is no conflict of interest of any kind; and that

he followed all pertinent ethical and legal pro-

cedures and requirements. All financial sources

are fully and clearly stated in the acknowledge-

ments section. A signed document has been

filed in the journal archives.

ACKNOWLEDGMENTS

I extend my gratitude to Juan Bosco Men-

doza and INPESCA for their invaluable assis-

tance and collaboration in data collection and

organization. Thanks to Rosa Soto and Marcus

Sheaves for their insightful advice on data anal-

ysis and manuscript preparation. I also thank

Keylin Gómez for her help with reviewing and

editing the final version of the manuscript. I

wish to acknowledge the Guadamuz family

members and Moisés Arana for their crucial

support in the field during data collection

efforts. We thank IDEA WILD for providing

equipment that contributed to this research.

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