Luz F. Jiménez-Segura

Automatic identification of species with neural networks

A new automatic identification system using photographic images has been designed to recognize fish, plant, and butterfly species from Europe and South America. The automatic classification system integrates multiple image processing tools to extract the geometry, morphology, and texture of the images. Artificial neural networks (ANNs) were used as the pattern recognition method. We tested a data set that included 740 species and 11,198 individuals. Our results show that the system performed with high accuracy, reaching 91.65% of true positive fish identifications, 92.87% of plants and 93.25% of butterflies. Our results highlight how the neural networks are complementary to species identification.

Regionally nested patterns of fish assemblages in floodplain lakes of the Magdalena river (Colombia).

We investigated if fish assemblages in neotropical floodplain lakes (cienagas) exhibit nestedness, and thus offer support to the managers of natural resources of the area for their decision making. The location was floodplain lakes of the middle section of the Magdalena river, Colombia. We applied the nested subset analysis for the series of 30 cienagas (27 connected to the main river and three isolated). All fish were identified taxonomically in the field and the matrix for presence–absence in all the lakes was used for the study of the pattern of nestedness. The most diverse order was Characiformes (20 species), followed by Siluriformes (19 species). Characidae and Loricaridae were the richest families. The species found in all the lakes studied were migratory species (17), and sedentary species (33). Two species (Caquetaia kraussii and Cyphocharax magdalenae) were widespread across the cienagas archipelago (100% of incidence). Nestedness analysis showed that the distribution of species over the spatial gradient studied (840 km) is significantly nested. The cienagas deemed the most hospitable were Simiti, El Llanito, and Canaletal. Roughly, 13 out of the 50 species caught show markedly idiosyncratic distributions. The resulting dataset showed a strong pattern of nestedness in the distribution of Magdalenese fishes, and differed significantly from random species assemblages. Out of all the measurements taken in the cienagas, only the size (area) and local richness are significantly related to the range of order of nested subset patterns (r=–0.59 and –0.90, respectively, at p < 0.01). Differential species extinction is suggested as the cause of a nested species assemblage, when the reorganized matrix of species occurring in habitat islands is correlated with the island area. Our results are consistent with this hypothesis.

Potamodromous migrations in the Magdalena River basin: bimodal reproductive patterns in neotropical rivers

Magdalena River basin potamodromous fishes have two annual reproductive seasons: the subienda in the first half of the year and the mitaca in the second. Both upstream migrations are c. 30-45 days long; after that, with the onset of the rainy season, fishes spawn and remain in the river (resident individuals) or start a downstream movement (the bajanza) to return to the Magdalena floodplain lakes (nursery, shelter and feeding grounds). Due to their particular gonad development the bocachico Prochilodus magdalenae and probably the comelón Leporinus muyscorum are physiologically able to undertake two annual basin migrations. In the presence of dams or hydropower structures, fishes are able to find alternative migration routes. Some species should be re-classified in their migratory behaviour.

Fish assemblages in floodplain lakes in a Neotropical river during the wet season (Magdalena River, Colombia)

A number of studies have pointed out that abiotic factors and recolonization dynamics appear to be more importantthanbioticinteractionsinstructuringriver-fishassemblages.Inthispaper,westudiedthefishassemblages in27floodplainlakes,withperennialconnectiontotheriver,inthemiddlesectionoftheMagdalenaRiver(Colombia), to examine spatial pattern in freshwater fish diversity in relation to some environmental parameters. Our objective was to examine relationships between floodplain-lake fish communities and environmental variables associated with lake morphology, water chemistry and river-floodplain connectivity in a large river-floodplain ecosystem. During the study, a total of 18237 fish were caught from 50 species (regional richness; 17 were migrants and 33 residents). In thepresentstudy,themostdiverseorderwasCharaciformeswith20species,followedbySiluriformes,with19species. CharacidaeandLoricaridaeweretherichestfamilies.Therangeofspeciesrichness(localrichness)variedbetweenfive and 39 species. Similarity of local assemblages (using the presence-absence data) depends on the distance between lakes. A positive relationship was observed between the Ln of the total abundance of each species and the number of lakes where they were found. Out of all the environmental parameters taken in the lakes, only the size (Log Area) and relative perimeter length are significantly related to local assemblage species richness. It has not been possible to demonstrate that the connectivity (distance) from lakes to the main river can be considered a predictor of the local richness.

Spatial distribution and seasonality of ichthyoplankton and anthropogenic debris in a river delta in the Caribbean Sea

Temporal changes in larval fish species composition and abundance compared with other components of the seston are described in four estuarine habitats in the Atrato Delta, Colombia. In comparison with zooplankton, fish larvae and egg density and anthropogenic debris abundance were low in the South Atrato Delta. Transparency, water temperature and chlorophyll a were the major factors influencing the spatiotemporal distribution of ichthyoplankton in the delta. The most abundant fish larvae were Astyanax sp. 1, Anchovia clupeoides, Cetengraulis edentulus, Anchoa sp., Bathygbius curacao, Dormitator maculatus, Hyporhamphus sp., Atherinella blackburni, Gobiosoma sp. 1 and Menticirrhus americanus (92·8% of total abundance). Spatial temporal analysis shows that in this delta, shrub (arracachal) and grass (eneal) habitats are important for freshwater and estuarine species, whilst mudflat and mangrove are important for estuarine species and estuarine-marine species, since most flexion and post-flexion stages of these species were found there. Anthropogenic debris density never surpassed the total ichthyoplankton density, but was ubiquitous. Shrub and mangrove habitats had higher densities of anthropogenic debris, since these are flood-stem habitats that trap solids.

Fish species from a micro-tidal delta in the Caribbean Sea.

A total of 66 fish species belonging to 32 families were recorded between November 2012 and April 2014 in the southern arm of the delta to the Atrato River. Total length (LT ; range: 1·7-48 cm), total mass (MT ), LT and MT relationships (b values ranged from 1·8 to 3·7, mostly with negative allometric growth), and LT frequency (for 25 species) were estimated for freshwater, estuarine and marine species. LT and MT of Porichthys pauciradiatus and Membras argentea are given for the first time and maximum LT records for 14 species exceed those in the literature.

Effects of environmental factors on reproductive seasonality of Magdalena River basin fish: need for answers in the ecophysiology

Magdalena River basin is the core of development and economy of Colombia, with about 80% o f the countrys population (32 million) depending on it. This basin is drained by the Magdalena River and 3 main tributary rivers: Cauca, Sogamoso, and San Jorge, covering an area of 257 438 km (nearly a quarter ofColombias territory) (GALVIS & MoncA 2007). According to its geomorphologic features, this basin has been divided in 3 main sectors: Upper, Middle, and Lower. Flood plain areas appear in Middle basin and grow in the Lower. The number o f fish species reported for this basin i s 167, some migratory and important for artisanal fisheries. Although fishery captures were nearly 80 000 tons in the 1970s, only one-fifth that amount is produced now (GALVIS & MoncA 2007). Studies on reproductive biology ofMagdalena River basin fishes are crucial for fisheries management and environmental protection programs. Based on some information on environmental factors and fish reproduction from different places in Magdalena River, we list some possible physiological pathways induced by environmental cues and recommend some experimental approaches that would help clarify such relationships.

Fish, Gymnotiformes, Apteronotidae, Apteronotus magdalenensis (Miles, 1945): distribution extension of an endangered endemic knifefish, in northern Colombia

The family Apteronotidae Jordan 1823 has recently been reviewed and currently has 60 species recognized as valid (Albert and Crampton 2009). This family has a widespread distribution in South America from Panama to Argentina (Albert 2003) and is the most diverse family of knifefishes in the Amazon basin (Albert 2001; Albert and Campos-da-Paz 1998). MaldonadoOcampo et al. (2008) documented thirty species of Apteronotidae from Colombia, eight endemic species from trans-Andean drainages and four species restricted to the Magdalena river basin (A. eschmeyeri de Santana et al 2004, A. magdalenensis, A. mariae (Eigenmann & Fisher 1914), and A. milesi de Santana & Maldonado-Ocampo 2005). However, our knowledge about the freshwater fishes of northern Colombia is still incomplete, and many areas have not been ichthyologically explored even today.