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Males of several fish species aggregate and vocalize together, increasing the detection range of the sounds and their chances of mating. In the Lusitanian toadfish (Halobatrachus didactylus), breeding males build nests under rocks in close proximity and produce hundreds of boatwhistles (BW) an hour to attract females to lay their demersal eggs on their nests. Chorusing behaviour includes fine-scale interactions between individuals, a behavioural dynamic worth investigating in this highly vocal fish. Here we present a study to further investigate this species’ vocal temporal patterns on a fine (individual rhythms and male-male interactions) and large (chorus daily patterns) scales. Several datasets recorded in the Tagus estuary were labelled with the support of an automatic recognition system based on hidden Markov models. Fine-scale vocal temporal patterns exhibit high variability between and within individuals, varying from an almost isochronous to an apparent aperiodic pattern. When in a chorus, males exhibited alternation or synchrony calling patterns, possibly depending on motivation and social context (mating or male-male competition). When engaged in sustained calling, males usually alternated vocalizations with their close neighbours thus avoiding superposition of calls. Synchrony was observed mostly in fish with lower mean calling rate. Interaction patterns were less obvious in more distanced males. Daily choruses showed periods with several active calling males and periods of low activity with no significant diel patterns in shallower intertidal waters. Here, chorusing activity was mainly affected by tide level. In contrast, at a deeper location, although tidal currents causes a decrease in calling rate, tide level did not significantly influence calling, and there was a higher calling rate at night. These data show that photoperiod and tide levels can influence broad patterns of Lusitanian toadfish calling activity as in other shallow-water fishes, but fine temporal patterns in acoustic interactions among nesting males is more complex than previously known for fishes. Fundação para a Ciência e Tecnologia - FCT info:eu-repo/semantics/publishedVersion

Evidences of changes in the fish fauna of Galician waters is documented based on the occurrence of 24 specimens belonging to eight warm affinity fishes. Information about the morphology and new findings of Desmodema polystictum (Trachipteridae), Halobatrachus didactylus (Batrachoididae), Dactylopterus volitans (Dactylopteridae) Anthias anthias (Serranidae), Callanthias ruber (Callanthiidae), Seriola rivoliana (Carangidae), Uranoscopus scaber (Uranoscopidae) and Sphyraena sphyraena (Sphyraenidae), is reported from Galician waters, where they are unusual or rare. Morphometric and meristic parameters confirmed the identification to species level of each specimen, which was also supported by DNA barcoding. In addition, sex identification by histology and oocyte measurements of several specimens were carried out. The record of D. polystictum supposes the first occurrence for Atlantic European waters and a new northernmost record of the distribution in the Eastern Atlantic. A Neighbour-Joining comparison of COI mitochondrial DNA sequences of D. volitans suggests the possible occurrence of an undescribed cryptic species or the existence of a species that could be resurrected from one of its many catalogued synonyms. According to the obtained rate, S. rivoliana is the species more commonly recorded. The gonad histological analysis proposes A. anthias and C. ruber as protogynous hermaphrodite species

Acoustic communication during agonistic behaviour is widespread in fishes. Yet, compared to other taxa, little is known on the information content of fish agonistic calls and their effect on territorial defence. Lusitanian toadfish males (Halobatrachus didactylus) are highly territorial during the breeding season and use sounds (boatwhistles, BW) to defend nests from intruders. BW present most energy in either the fundamental frequency, set by the contraction rate of the sonic muscles attached to the swimbladder, or in the harmonics, which are multiples of the fundamental frequency. Here we investigated if temporal and spectral features of BW produced during territorial defence reflect aspects of male quality that may be important in resolving disputes. We found that higher mean pulse period (i.e. lower fundamental frequency) reflected higher levels of 11-ketotestosterone (11KT), the main teleost androgen which, in turn, was significantly related with male condition (relative body mass and glycogen content). BW dominant harmonic mean and variability decreased with sonic muscle lipid content. We found no association between BW duration and male quality. Taken together, these results suggest that the spectral content of fish agonistic sounds may signal male features that are key in fight outcome. Fundação para a Ciência e Tecnologia (FCT)

Male reproductive success often depends on male attributes and resource quality. Here, we examined male preference for nest size in the Lusitanian toadfish, a nest-guarding fish with parental care. We also investigated the combined effect of male length and nest size in male breeding success. Approximately 80 shelters with five different sizes were placed on an intertidal zone of the Tagus estuary. Nests were checked every fortnight at spring low tides for occupation, nest-holder length, and number of eggs. Males did not select for the larger nests despite their availability but showed size assortative nest choice. Only nest size was a significant predictor of clutch size in occupied nests and it explained 60% of the variability in the number of obtained eggs. Male length and the interaction of male length and nest size did not have a significant effect on male reproductive success. These results suggest that although nest size is key to male's reproductive success, the choice for nest size results from a trade-off between accrued costs of offspring care or risk of a nest take-over and possible benefits of increased fitness.

In this paper, we compare the populations of the Lusitanian toadfish Halobatrachus didactylus along the Portuguese shore, using a putative fragment of the mito- chondrial control region and the first intron of the S7 ribosomal protein gene. This demersal species ranges from the tropical West African coast to the Iberian Peninsula and the Mediterranean, having its northern limit in the Tagus River. For the putative control region, a single haplotype occurs in all fish from Tagus and Sado (the location immediately to the south) with a clear increase in diversity to the South, peaking at Algarve (south Portugal). The data seem to point to a very recent Holocenic colonization of Tagus and Sado from the South (possibly Algarve). We suggest that even small oscillations in sea surface tem- perature (SST) may cause local extinctions and subsequent recolonizations in populations of thermophilic fish that are at the cold limit of their distributions.

The Lusitanian toadfish, Halobatrachus didactylus, like other batrachoidids, is a benthic fish species with nesting behaviour during the breeding season. During this prolonged period it engages in mating activities and remains in the nest providing parental care. It is not known whether males feed while providing parental care but it is likely that their limited mobility may restrict their diet and influence their fitness. As a consequence, egg cannibalism could occur as a life-history strategy. The aim of the present study is to ascertain the feeding behaviour of nesting males, in comparison to mature non-nesting males, and to identify potential life-history traits related to egg cannibalism. Nest-holders were sampled from artificial nests placed in an intertidal area of the Tagus estuary, only exposed during spring low tides. The diet of nest-holders was compared with that of non-nesting mature males from the same area, captured by otter trawl. The present study demonstrates that despite their constrained mobility nest-holders feed during the breeding season, although in a more opportunistic fashion than non-nesting males. Nest-holders showed a generalist feeding behaviour, with a more heterogeneous diet. Egg cannibalism was not related to male condition, paternity or brood size but showed a higher incidence early in the season when water temperatures were lower. The results suggest a possible seasonal trade-off strategy between care and energy recovery, triggered by environmental factors, where under unfavourable conditions to sustain viable eggs the male may recover energy by eating eggs, thus benefiting future reproductive success, later in the season. Fundação para a Ciência e a Tecnologia (FCT)

Fish-based indices are becoming important bioassessment tools for estuaries since the European Water Framework Directive included fish as a biological quality element to be monitored for the assessment of ecological status of those systems. In particular, data on species composition and abundance of the ichthyofauna must be used to evaluate the ecological status of European estuaries, but other factors like measures of fish health are also considered important metrics. These indicators of fish health include infections by parasites. The common goby, Pomastoschistus microps , and the Lusitanian toadfish, Halobatrachus didactylus , are fairly sedentary fish, very abundant in Portuguese estuaries, and were used to investigate if parasitism in fishes in transitional waters is a good metric to reflect anthropogenic impacts in the environment. No significant relationships were observed between the parasite levels in these two species and the intensity of human pressures, either at a large or small spatial scale. Results obtained also are contrary to the generalized idea that a higher proportion of parasitized fish necessarily reflects a decrease in their condition as a result of habitat degradation. A high degree of temporal and ontogenetic variability in the parasite levels of both P. microps and H. didactylus was detected, which make it difficult to establish the scores for this hypothetical metric even if significant relationships between parasite levels and human pressures are identified in the future. Therefore, the present work does not uphold the hypothesis that parasitism in fish is a good metric to assess ecological water quality in transitional waters.

The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801), is a subtropical sound-producing marine teleost that inhabits estuaries and other brackish water ecosystems in its northern distribution area. The relative isolation of populations within estuaries may cause important modifications in the bio-ecology of this species. The males of this species present two morphotypes which are more accurately distinguishable during the reproductive season. In the Tagus estuary population, the two types of reproductive males were present: type I, the “characteristic” morphotype, and type II, the alternative morphotype. The opportunistic males had more developed testis while type I males had more developed accessory glands. Type I males presented more developed swimbladders and larger body size and live longer than type II males. On the contrary, type II males grew faster and matured earlier. The feeding habits of the two male morphotypes were similar during the reproductive season but differences were found between reproductive specimens and non-reproductive specimens. The diet of reproductive specimens was mainly composed of benthic prey in contrast to predominance of nectobenthic prey in the diet of non-reproductive specimens. The females of H. didactylus generally had an intermediate pattern between the two male morphotypes. The percentage of type II males tended to be higher in denser areas of the estuary. In comparison with populations from different size ecosystems, smaller ecosystems revealed important modifications on the bio-ecology of the species due to the increased competition for nesting sites and mating partners, favouring alternative male tactics.

Activity rhythms and movement patterns of 10 adult specimens of the Lusitanian toadfish, Halobatrachus didactylus (Bloch & Schneider), were studied in the River Mira estuary (Portugal) using pressure-sensitive data-loggers and acoustic transmitters. Laboratory experiments were performed to assess the applicability of the sampling methodology to track the Lusitanian toadfish movements. Field results confirmed that the species usually displays a sedentary behaviour, although revealing a stronger disposition to perform greater longitudinal movements than it was formerly believed. Frequency of movements was influenced by the circadian cycle, tidal stage and type of tide. Lomb-Scargle periodograms revealed significant daily periodicity in all the specimens studied. Two fish displayed significant intercalary rhythms that could be related with tidal cycle. This study also indicates that this species does not exclusively adopt a sit and wait predation behaviour, but probably undertakes an active search for food.

The function of fish sounds in territorial defence, in particular its influence on the intruder's behaviour during territorial invasions, is poorly known. Breeding Lusitanian toadfish males (Halobatrachus didactylus) use sounds (boatwhistles) to defend nests from intruders. Results from a previous study suggest that boatwhistles function as a 'keep-out signal' during territorial defence. To test this hypothesis we performed territorial intrusion experiments with muted Lusitanian toadfish. Subject males were assigned to three groups: muted, sham and unmanipulated. Males were muted by making a cut and deflating the swimbladder (the sound producing apparatus) under anaesthesia. Sham males suffered the same surgical procedure except the swimbladder cut and deflation. Toadfish nest-holder males reacted to intruders mainly by emitting sounds (sham and unmanipulated) and less frequently with escalated fights. When the nest-holder produced a boatwhistle, the intruder fled more frequently than expected by chance alone. Muted males experienced a higher number of intrusions than the remaining groups probably due to their inability to vocalise. Together, our results show that fish acoustic signals are effective deterrents in nest/territorial intrusions, similar to bird song.

Early diagenetic processes and anthropogenic activities are responsible for metal enrichment in estuarine sediments. The Tagus estuary (Portugal) is no exception, and as a result of past and present pressures, surface sediment contamination is still an issue in some areas. Since such metal loads may be incorporated by benthic organisms, this study analyzed the accumulation of trace metals in the Lusitanian toadfish (Halobatrachus didactylus) in the Tagus estuary. In order to determine the role played by the seasonal reproductive cycle of the Lusitanian toadfish in the bioaccumulation process of trace metals in its tissues, the concentrations of Cd, Co, Cr, Cu, Ni, Pb and Zn were determined in the liver of male and female specimens captured during reproductive and non-reproductive periods. The results showed that metal accumulation in the liver was related simultaneously with gender and season, with females having higher levels of Cd, Cu and Zn during the reproductive period. The metabolic roles of Cu and Zn in embryonic development may explain such results, as both metals accumulated in the female liver to be transported to the gonads later on. Cd, on the other hand, does not have a metabolic role, and the higher concentrations of this metal found in spawning females could be related to the high affinity of Cd to vitellogenin, which is produced in the liver. To assess the species’ potential as an indicator of metal contamination, the concentrations of the seven elements were compared in the muscle tissue of adult, type I males (age ≥5), from two areas with distinct sediment metal loads. Non-essential metals in the muscle reflected the same differences between areas that were found in the sediment samples, evidencing H. didactylus as a potential indicator of those elements bioavailability from the sediment. The results showed that the muscle tissue of adult specimens of a relatively sedentary species such as H. didactylus is a useful indicator of long term accumulation of trace metals. On the contrary, liver concentrations of trace metals showed variation according to the reproductive status, which could lead to overestimate of the environmental status concerning trace metals bioavailability. Spawning season and liver tissue should thus be avoided in biomonitoring studies targeting this benthic fish.

SUMMARY: The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801), is distributed from the Ghana coast to the Iberian Peninsula, being particularly abundant on the south coast of Portugal. The differentiation of this species along the Portuguese coast was assessed through the analysis of 10 samples, considering morphological characters (20 morphometric and 16 meristic) and genetic markers (10 allozymes, 11 loci). Southern samples included estuaries and their adjacent coastal areas, given that this species inhabits both environments, whereas western samples only comprised estuaries. Morphometric and meristic data discriminant analysis evidenced some differentiation between estuarine and coastal populations. This was not entirely corroborated by the genetic analysis, which showed an overall pattern of low FST (0.042) and Nei’s genetic distance, even between geographically distant areas. However, higher values of these parameters were found between estuaries of the south coast and their adjacent coastal areas, suggesting that estuarine systems play a major role in such differentiation. Results are discussed regarding toadfish life-history pattern and Portuguese coast geomorphology, giving an insight into the biological and environmental factors influencing population sub-structuring.

Seasonal variation of sound production, which includes boatwhistles, grunts, croaks and double croaks, was studied in the Lusitanian toadfish Halobatrachus didactylus. Boatwhistles were emitted during the mating season in contrast with the other sound types, which were emitted all year round.

Summary A total of 366 Halobatrachus didactylus (Bloch & Schneider 1801) individuals were obtained between September and November 2000 from commercial fishing vessels at eight localities along the Portuguese coast and analysed for metazoan parasite infections. Three species of parasites were found: Hysterothylacium aduncum Rudolphi 1802; Progrillotia dasyatidis Beveridge et al. 2004, which constitutes a new host record for the Lusitanian toadfish; and Nerocila orbignyi Guerin-Meneville 1829. Prevalence and mean abundance were determined for the total fish population in each sample. Significant differences in the number of parasitized fish among the samples analysed indicate differences in the H. didactylus populations along the Portuguese coast. The cluster analysis performed to prevalence data pointed out two major clusters: one composed of mainly estuarine samples and one that grouped samples from coastal areas; this is in agreement with the results obtained by morphological and genetic analysis performed for the same samples.

A total of 207 specimens of Lusitanian toadfish Halobatrachus didactylus from six different localities were analysed in terms of morphometric and meristic characters in order to investigate the hypothesis of population fragmentation on the Portuguese coast. This study confirmed the relative isolation between the Algarve populations and those from the western estuaries, which also showed a high degree of discrimination among them. Morphometric characteristics were much more adequate than meristic characters for a good separation of these populations. The most relevant morphometric characteristics for separation between H. didactylus populations were head width, interorbital width and pelvic fin length. These three variables were very useful for separation between western populations and seem to play an important role in species feeding activity. The caudal peduncle development is mainly related to the specimen´ swimming ability and was particularly relevant for discrimination between northern and southern populations and between estuarine and adjacent marine populations, apparently due to differences in hydrodynamic conditions. Meristic variation is mostly of a latitudinal nature (mainly nasal tentacles and pores on the lower jaw) but some differences between estuarine and marine populations (principally fin rays counts) related to water temperature were also observed. Para investigar la hipótesis de fragmentación de las poblaciones portuguesas de sapo lusitánico Halobatrachus didactylus, se han analizado un total de 207 ejemplares de esta especie, provenientes de seis localidades distintas, a nivel de sus características morfométricas y merísticas. El estudio ha confirmado el aislamiento relativo de las poblaciones del Algarve y de sus homólogas de los estuarios de la costa occidental, demostrando estas últimas, de igual modo, un elevado grado de aislamiento entre ellas. Las características morfométricas se han revelado mucho más adecuadas que los caracteres merísticos, para la separación de poblaciones de la especie. De las primeras, las más relevantes son la anchura de la cabeza, la distancia interorbital y la longitud de la aleta pélvica. Estas tres características, que parecen desempeñar un papel importante en la alimentación de la especie, son especialmente útiles en la discriminación de las poblaciones de la costa occidental. El desarrollo del pedúnculo caudal está sobretodo relacionado con la capacidad natatoria y es muy relevante para la separación entre poblaciones septentrionales y meridionales, y entre las originarias de medios estuarinos y marinos adyacentes, aparentemente, debido a las diferencias en las condiciones hidrodinámicas que se verifican en estas zonas. Las variaciones en los caracteres merísticos tienen, fundamentalmente, un origen latitudinal (sobretodo los tentáculos nasales y los poros submaxilares), aunque se hayan encontrado también diferencias entre las poblaciones estuarinas y marinas (principalmente en el número de rayos de las aletas) atribuibles a los distintos regímenes térmicos de estos ambientes.

The Vasa gene is essential for germ cell development in eukaryotes. It encodes a RNA helicase, a member of the DEAD box protein family. Using the RACE method, we cloned the Vasa cDNA of the Lusitanian toadfish Halobatrachus didactylus, and analyzed quantitative and qualitative Vasa expression and its protein immunolocalization. We reported a main product of about 2.4 kb which encodes a protein of 615 amino acids, but other minority Vasa products were also identified by RACE-PCR. This gene is predominantly expressed in the ovaries and testes, although some relatively low extragonadal expression levels have also been identified. In situ hybridization and immunolocalization analysis during gametogenesis in the testes showed that toadfish Vasa mRNA was detected in spermatogonia, spermatocytes and spermatids. However, in the ovaries, Vasa mRNA was detected in early vitellogenic oocytes and in more advanced vitel-logenic stages, showing a very weak signal in oogonia, whereas the Vasa protein was evidenced in the cytoplasm of oogonia and previtellogenic oocytes, becoming weaker as the vitellogenic and maturation processes progress. These results suggest that toadfish Vasa homologues can play an important role in gametogenesis and germ cell development, but it could also be functionally implicated in other processes that are not as well known. © The authors 2014., This work was financed by Proyecto de Excelencia (RNM-03074; Consejería de Inno- vación, Ciencia y Empresa, Junta de Andalucía, Spain). M.Ú-M. was supported by a CSIC JAE-Predoc fellowship.

The biology of Halobatrachus didactylus has received special attention during recent years because of its use as an experimental species in toxicology and cardiology experiments. The object of the present work is to supply basic information about the reproductive biology of this species. Samples were collected in Cadiz Bay between February 1999 and March 2000. A total of 901 specimens (440 females and 461 males) were examined. Sex ratio did not differ from the theoretical 1:1, except in May 1999, and February 2000. Minimum size at maturity was 191 mm total length for females and 160 mm total length for males. Approximately 50 % of the population matured at 262 mm for females and 302 mm for males. The spawning season extends from March to August, with a peak in May-June. Fecundity ranged from 227 to 1233 eggs/female, and was related to body length and weight. Length-weight relationship for the sexes differed, and showed positive allometry. The condition factor showed a minimum in the spawning season, which is interpreted as the result of mobilization of somatic energy reserves needed for reproductive development, and/or the use of reserves stored in the body as a source of energy in spawned fish, influenced by reduced feeding during this period.

Estuarine fish communities are usually used in an ecological monitoring context to infer the environmental changes ocurring in estuarine environments. In the present paper several analyt- ical tools, namely community analysis indices, species-ranking methods and multivariate ordination techniques, were applied to time series data for the Tagus fish community for 2 periods: 1979 to 1981 and 1995 to 1997. Assessment of the relative importance of anthropogenic versus naturally induced fluctuations is made difficult by the range of natural short-term variations. For the Tagus case study, multivariate ordination techniques, rather than the ranking methods and indices analyzed, provide a good indicator of long-term changes. The major trends in the changes observed in this fish commu- nity were a decrease in abundance for several species that use the estuary as a nursery area and an increase in some resident species, namely Gobius spp. and Halobatrachus didactylus. Several species with southern European affinities have increased their importance within the Tagus estuarine fish community.

Several batrachoidids have been known to produce sounds associated with courtship and agonistic interactions, and their repertoires have been studied acoustically and behaviourally. In contrast, sound production of the Lusitanian toadfish Halobatrachus didactylus, although often noted, has not been acoustically studied. This sedentary predator of Northeastern Atlantic coastal waters is usually found in sandy and muddy substrates, under rocks or crevices. Sound recordings were made in Ria Formosa, a lagoon complex in southern Portugal. The sound producing apparatus was studied in adult individuals of both sexes captured by local fishermen. It is shown that this species produces acoustic emissions similar to other batrachoidids. It produces a long, rhythmical, tonal sound, often in choruses, which is comparable to the boatwhistle or hum signals of Opsanus and Porichthys, and a complex of signals that were classified as grunts, croaks, double croaks and mixed calls (‘grunt-croak’). As in other toadf...

The relation between acoustic signaling and reproductive success is important to understand the evolution of vocal communication systems and has been well studied in several taxa but never clearly shown in fish. This study aims to investigate whether vocal behavior affects the reproductive success in the Lusitanian toadfish (Halobatrachus didactylus) that relies on acoustic communication to attract mates. We recorded 56 nest-holding (type I) males during the breeding season and analyzed the calling performance and acoustic features of the mate advertising sounds (boatwhistles) exhibited over circa 2 weeks. Hormonal levels of the subjects and the number of eggs (reproductive success) present in the respective nests were quantified. Nesting males attracted both females and other males, namely smaller type I males with significantly lower total length (TL), body condition, sonic muscle mass, gonad mass, and accessory glands mass. Calling rate (CR), calling effort (CE) (% time spent calling), and sound dominant frequency were significantly higher in nesting males with clutches than in those without clutches. Sex steroids (11-ketotestosterone and testosterone) were not correlated with vocal parameters or number of eggs. Maximum CR and CE were the best predictors of the number of eggs. In addition, these vocal variables were best explained by male's TL, condition, and sonic muscle mass. We provide first evidence that vocal behavior significantly determines reproductive success in a vocal fish and show that acoustic signaling at higher and constant rates can operate as an indicator of the male's size and body condition and probably of elevated motivation for reproduction. Science and Technology Foundation, Portugal [PDCT/MAR/58071/2004, UID 331/94, SFRH/BD/30491/2006, SFRH/BPD/41489/2007] info:eu-repo/semantics/publishedVersion

article i nfo In many fish species in which males guard nests with their eggs, parental care directed to genetically unrelated offspring may arise for example from nest takeovers or cuckoldry. Lusitanian toadfish (Halobatrachus didactylus) has exclusive male parental care and face intensive nest competition during the breeding season that may lead to care of foster eggs. Males of this species use visual displays and sounds when defending their nests frequently resulting in expulsion of the intruder without escalated confrontation. In this study we intended to investigate the existence of alloparental care in Lusitanian toadfish, a behavior whose adaptive significance is still poorly understood. Fish were randomly assigned to three different treatments: parental males in nests with their eggs, parental males with foster eggs and parental males without eggs. Nests with eggs with no nest holder or with females were used as controls. We performed three territorial intrusions over periods of 15 days and observed the acoustic and visual behaviors of residents and intruders. Egg survival was tallied from nests' photographs in all groups. Circulating steroid levels were measured in the three test groups and in another set of non-manipulated males. There were no differences in acoustic and visual territo- rial defense behaviors among treatments. Egg survival was similar between males (parental and alloparental) and significantly higher than in nests with no nest-tender. Females presented intermediate egg survival. All groups presented similar levels of testosterone and alloparental males showed higher 11-ketotestosterone levels but within the range of levels observed in non-manipulated males. Cortisol levels were similar in all male groups suggesting that experiments did not increase fish stress. The present results suggest the existence of alloparental care in this species.

Signal attributes should show different degrees of variability depending on the information to be conveyed. Species identity is usually associated with stereotyped features of a signal, whereas other types of information such as individual quality and motivation are associated with signal plasticity. Lusitanian toadfish males form aggregations during the breeding season and emit a tonal advertisement call (the boatwhistle) to attract mates to their nests. We test the hypothesis that the boatwhistle can convey information both on individual identity and motivation by checking how signal parameters vary with time. We study how the physical (tide level) and social (calling alone or in a chorus) environments and male calling rate affect this advertisement signal and how all these external and internal factors (environment, social and male motivation) blend to modulate the Lusitanian toadfish’s advertisement call. Boatwhistles of each male were very stereotyped in short periods of time (minutes), but intra-male signal variability greatly increased in a longer time scale (days). Nevertheless, significant differences among males could still be found even in a long time scale. Pulse period was the acoustic feature that most contributed to discriminate among males. Tide level and male calling rate modulated boatwhistle characteristics, and there was a differential effect of tide on call attributes depending on male calling rate. Social acoustic environment only affected calling rate. These results suggest that inter-individual differences in call characteristics and call plasticity may mediate both male– male assessment and mate choice.

10 pages, 7 figures, 5 tables., [EN] Age, growth and mortality of the toadfish, Halobatrachus didactylus, were determined by examination of the whole sagittal otoliths of fish sampled in the Bay of Cádiz (southwestern Spain) from March 1999 to March 2000. A total of 844 specimens (425 males, 416 females, and 3 of indeterminate sex), ranging from 95 to 470 mm in total length were examined. Eighty-nine percent of the otoliths could be read allowing an age estimation. The opaque zone was formed between April and May coincident with the maximum reproductive peak, while the translucent zone formed mainly in summer-fall (June to December). Maximum ages for males and females were 12 and 10 years, respectively. The samples were dominated by 2- to 6-year-old specimens. Males matured at an age of approximately 2 years and females at 3 years. Fish total length and otolith radius were closely related (r2>0.80). The von Bertalanffy growth curve was used to describe growth. The parameters were derived from back-calculated length-at-age. Significant differences in the growth parameters were found between sexes (in males L∞ = 477.06 mm, K = 0.15 and t0 = -0.59; in females L∞ = 363.69 mm, K = 0.20 and t0 = -0.75). Although the growth analysis revealed that this species is slow-growing, males reached larger sizes than females. Females appeared to experience higher natural mortality rates than males., [ES] Se determinó la edad y se estimaron los parámetros de crecimiento y la tasa de mortalidad natural de H. didactylus con base en el análisis de los otolitos sagita de ejemplares capturados mensualmente en la Bahía de Cádiz (suroeste de España) entre marzo de 1999 y marzo de 2000. Se examinó un total de 844 ejemplares (425 machos, 416 hembras, y 3 con sexo indeterminado), con tallas que oscilaron entre 95 y 470 mm de longitud total. El 89% de los otolitos analizados resultó legible y permitió asignar un número de anillos. El crecimiento anual estuvo representado por una zona opaca y una translúcida. La zona opaca se forma entre abril y mayo, coincidiendo con el máximo pico reproductivo, mientras que la zona translúcida se forma principalmente en verano-otoño, (junio-diciembre). El recuento de zonas anuales en los otolitos permitió establecer hasta 12 grupos de edad en los machos y 10 en las hembras. En ambos casos predominaron los ejemplares con 2–6 años. Los machos alcanzan la madurez sexual, aproximadamente, a los 2 años de edad y las hembras a los 3 años. La longitud total del pez y el radio de los otolitos estuvieron fuertemente relacionados r2>0.80. El crecimiento individual fue determinado mediante ajuste al modelo de von Bertalanffy. Los parámetros de crecimiento estimados para machos y hembras a partir de las longitudes a edad pretérita para cada edad fueron significativamente diferentes (machos: L∞= 477.06 mm; k= 0.15 y t0= -0.59; hembras: L∞= 363.69 mm; k= 0.20 y t0= -0.75). Aunque puede considerarse como una especie de crecimiento lento, los machos alcanzan mayores longitudes que las hembras. Las tasas de mortalidad natural estimadas fueron ligeramente superiores en las hembras., This study received financial support from the Instituto de Ciencias Marinas de Andalucía – Consejo Superior de Investigaciones Científicas, Spain and the Consejo de Investigación, Universidad de Oriente, Venezuela.

In some marine fishes, males migrate from deeper to littoral water to breed, where they defend nests and provide parental care. In this study, we describe seasonal patterns of shelter occupation in estuarine shallow waters and assess social aggregation in the Lusitanian toad- Wsh (Batrachoididae), a vocal species with male parental care. Occupation of intertidal shelters was restricted to the breeding season but adult fish remained in subtidal regions during the non-reproductive season and they produced sounds throughout the year. Intertidal shelters were aggregated with up to five shelters found per 2-m segment of an 80-m transect. This aggregation probably resulted from social attraction since many segments were found unoccupied. Moreover, shelters contained on average two fish (maximum of nine). Based on size, shelters with multiple fish seemed to contain females, or possibly sneakers, but also more than one type I male inside, indicating a high social tolerance for conspecifics.