Call recognition and individual identification of fish vocalizations based on automatic speech recognition: An example with the Lusitanian toadfish.

The study of acoustic communication in animals often requires not only the recognition of species specific acoustic signals but also the identification of individual subjects, all in a complex acoustic background. Moreover, when very long recordings are to be analyzed, automatic recognition and identification processes are invaluable tools to extract the relevant biological information. A pattern recognition methodology based on hidden Markov models is presented inspired by successful results obtained in the most widely known and complex acoustical communication signal: human speech. This methodology was applied here for the first time to the detection and recognition of fish acoustic signals, specifically in a stream of round-the-clock recordings of Lusitanian toadfish (Halobatrachus didactylus) in their natural estuarine habitat. The results show that this methodology is able not only to detect the mating sounds (boatwhistles) but also to identify individual male toadfish, reaching an identification rate of ca. 95%. Moreover this method also proved to be a powerful tool to assess signal durations in large data sets. However, the system failed in recognizing other sound types.

Darkedge midshipman Porichthys analis (Batrachoidiformes: Batrachoididae), a common shrimp-bycatch fish from the Gulf of California

Shrimp fishery bycatch of the Gulf of California constitutes a wide variety of highly unknown fish, crustacean, and mollusk species with very low or null economic value, in contrast to those of commercial interest. However, there are no studies yet on the role of these low economic valued species have in the community structure and function, together with their possible effect on commercial populations. With the aim of contributing to the knowledge of Darkedge Midshipman fish Porichthys analis, the most common waste species in this fishery, we estimated some population characteristics. For this purpose, we obtained shrimp-bycatch fish during the 2004-2005 fishing season and performed some research surveys. A total of 1 725 Darkedge Midshipman were captured from 350 bycatch samples. Individual size ranged from 43-352mm SL. The weight to standard length relationship was determined as W=0.000092SL3.0509. Von Bertalanffy’s growth coefficient indicated a moderate growth rate (K=0.5) with an estimated asymptotic length ofL∞=352mm standard length, and a longevity of 6yr. Natural mortality was estimated as 0.97 and total mortality as 4.67. The recruitment pattern, as estimated by ELEFAN II, was extended over the year, peaking during spring and summer seasons. Sexual proportion of male:female was 1.65:1. Mature organisms appeared from August to March, and length at maturity was 157mm SL, which is larger than the mean size at capture 135mm SL. We concluded that the species is indirectly protected by its own bathymetric distribution and the off-shrimping season. This is the first study that considers population characteristics from this common but still unknown species.

A diferencia de las especies de interés comercial, la historia de vida de los peces no comerciales es casi desconocida a pesar de su potencial importancia en la estructura y función de la comunidad. Para contribuir al conocimiento de estas especies se estimaron algunas características poblacionales del chupalodo Porcihchty sanalis. La fauna de acompañamiento de la pesquería del camarón en el Golfo de California está constituida por especies poco conocidas y de escaso valor comercial. Las especies de la familia Batrachoididae son frecuentemente utilizadas como animales experimentales, pero poco se sabe de P. analis. De esta manera a partir de la fauna de acompañamiento se recolectaron 1 725 organismos y se determinó la relación talla-peso W=0.000092SL3.0509. Mediante ELEFAN I, se estimó un crecimiento moderado (K=0.5/año) con una longitud asintótica mayor que la observada reportada anteriormente (L∞=352mm SL) y una longevidad de 6 años. La mortalidad natural se estimó en M=0.97 la total en Z=4.67. El patrón de reclutamiento fue mayor durante primavera-verano. La proporción sexual M:F fue 1.65:1 y la talla media de primera madurez fue de 157mm SL mayor que la talla media de captura 135mm SL. Este es el primer reporte que considera las características poblacionales de esta especie común, pero poco conocida.

Darkedge midshipman Porichthys analis (Batrachoidiformes: Batrachoididae), a common shrimp-bycatch fish from the Gulf of California.

Shrimp fishery bycatch of the Gulf of California constitutes a wide variety of highly unknown fish, crustacean, and mollusk species with very low or null economic value, in contrast to those of commercial interest. However, there are no studies yet on the role of these low economic valued species have in the community structure and function, together with their possible effect on commercial populations. With the aim of contributing to the knowledge of Darkedge Midshipman fish Porichthys analis, the most common waste species in this fishery, we estimated some population characteristics. For this purpose, we obtained shrimp-bycatch fish during the 2004-2005 fishing season and performed some research surveys. A total of 1 725 Darkedge Midshipman were captured from 350 bycatch samples. Individual size ranged from 43-352mm SL. The weight to standard length relationship was determined as W=0.000092SL(3.0509). Von Bertalanffy's growth coefficient indicated a moderate growth rate (K=0.5) with an estimated asymptotic length of L(infinity) = 352mm standard length, and a longevity of 6yr. Natural mortality was estimated as 0.97 and total mortality as 4.67. The recruitment pattern, as estimated by ELEFAN II, was extended over the year, peaking during spring and summer seasons. Sexual proportion of male:female was 1.65:1. Mature organisms appeared from August to March, and length at maturity was 157mm SL, which is larger than the mean size at capture 135mm SL. We concluded that the species is indirectly protected by its own bathymetric distribution and the off-shrimping season. This is the first study that considers population characteristics from this common but still unknown species.

Sequence characterization and phylogenetic analysis of the 5S ribosomal DNA in species of the family Batrachoididae.

5S ribosomal DNA (rDNA) sequences were analyzed in four species belonging to different genera of the fish family Batrachoididae. Several 5S rDNA variants differing in their non-transcribed spacers (NTSs) were found and were grouped into two main types. Two species showed both types of 5S rDNA, whereas the other two species showed only one type. One type of NTS of Amphichthys cryptocentrus showed a high polymorphism due to several deletions and insertions, and phylogenetic analysis showed a between-species clustering of this type of NTS in Amphichthys cryptocentrus. These results suggest a clear differentiation in the model of 5S rDNA evolution of these four species of Batrachoididae, which appear to have been subject to processes of concerted evolution and birth-and-death evolution with purifying selection.

Chromosomal mapping of the major and minor ribosomal genes, (GATA)n and U2 snRNA gene by double-colour FISH in species of the Batrachoididae family.

In the present study dual-colour fluorescence in situ hybridization (FISH) was performed to study the chromosomal distribution of 18S and 5S rDNAs, (GATA)(n) and 5S rDNA, and U2 snRNA and 18S rDNA in four species of Batrachoididae family: Amphichthys cryptocentrus, Batrachoides manglae, Porichthys plectrodon and Thalassophryne maculosa. The 18S rDNA signals were present in only one pair of chromosomes in all the four Batrachoididae species. The 5S rDNA was mapped on one pair of chromosomes, except in B. manglae, which showed a hybridization signal in two pairs. The two ribosomal genes are located on different chromosome pairs, except in A. cryptocentrus, in which they appear co-located. In all the cases, the (GATA)(n) probe produced disperse hybridization signals in all four species. The U2 snRNA signals appear very widely scattered in A. cryptocentrus, P. plectrodon, but show a degree of clustering in a specific chromosome pair in B. manglae. In T. maculosa, they are thinly dispersed and strong hybridization signals are observed co-located to the 18S rDNA-bearing chromosomes. Finally, a double-colour FISH with U2 snRNA and 5S rDNA probes was performed in B. manglae, and this showed that these genes were not co-located. These results have been compared with those from another Batrachoididae species, and evolutive processes of these species are discussed.

Novel vocal repertoire and paired swimbladders of the three-spined toadfish, Batrachomoeus trispinosus: insights into the diversity of the Batrachoididae.

Toadfishes (Teleostei: Batrachoididae) are one of the best-studied groups for understanding vocal communication in fishes. However, sounds have only been recorded from a low proportion of taxa within the family. Here, we used quantitative bioacoustic, morphological and phylogenetic methods to characterize vocal behavior and mechanisms in the three-spined toadfish, Batrachomoeus trispinosus. B. trispinosus produced two types of sound: long-duration 'hoots' and short-duration 'grunts' that were multiharmonic, amplitude and frequency modulated, with a dominant frequency below 1 kHz. Grunts and hoots formed four major classes of calls. Hoots were typically produced in succession as trains, while grunts occurred either singly or as grunt trains. Aside from hoot trains, grunts and grunt trains, a fourth class of calls consisted of single grunts with acoustic beats, apparently not previously reported for individuals from any teleost taxon. Beats typically had a predominant frequency around 2 kHz with a beat frequency around 300 Hz. Vocalizations also exhibited diel and lunar periodicities. Spectrographic cross-correlation and principal coordinates analysis of hoots from five other toadfish species revealed that B. trispinosus hoots were distinct. Unlike any other reported fish, B. trispinosus had a bilaterally divided swimbladder, forming two separate swimbladders. Phylogenetic analysis suggested B. trispinosus was a relatively basal batrachoidid, and the swimbladder and acoustic beats were independently derived. The swimbladder in B. trispinosus demonstrates that toadfishes have undergone a diversification of peripheral sonic mechanisms, which may be responsible for the concomitant innovations in vocal communication, namely the individual production of acoustic beats as reported in some tetrapods.

Chromosomal mapping of the major and minor ribosomal genes, (GATA)n and (TTAGGG)n by one-color and double-color FISH in the toadfish Halobatrachus didactylus (Teleostei: Batrachoididae).

The karyotype of Halobatrachus didactylus presents 46 chromosomes, composed of eight metacentric, 18 submetacentric, four subtelocentric, and 16 acrocentric chromosomes. The results of FISH showed that the major ribosomal genes were located in the terminal position of the short arm of a large submetacentric chromosome. They also showed a high variation in the hybridization signals. The products of amplification of 5S rDNA produced bands of about 420 pb. The PCR labeled products showed hybridization signals in the subcentromeric position of the long arm of a submetacentric chromosome of medium size. Double-color FISH indicated that the two ribosomal families are not co-located since they hybridized in different chromosomal pairs. Telomeres of all the chromosomes hybridized with the (TTAGGG)n probe. The GATA probe displayed a strong signal in the long arm of a submetacentric chromosome of medium size, in the subcentromeric position. The double-color FISH showed that the microsatellite GATA and the 5S rDNA gene are located in different chromosomal pairs. The majority presence of GATA probes in one pair of chromosomes is unusual and considering its distribution through different taxa it could be due to evolutionary mechanisms of heterochromatine accumulation, leading to the formation of differentiated sex chromosomes.