Population structure of the pearly razorfish, <em>Xyrichtys novacula</em> (Actinopterygii: Labridae), in sand-seagrass mosaics: spatial variation according to habitat features and sampling techniques

Abstract

Summary:Habitat structure affects the distribution of fishes, particularly across reef-dominated habitats, but few studies have connected patterns in the abundance of soft-bottom fishes with the structure of the habitat. The spatial and temporal patterns of variation in the abundance, biomass and population structure of the pearly razorfish, Xyrichtys novacula, inhabiting sand-Cymodocea nodosa seagrass mosaics were described through two complementary techniques: underwater visual counts and seine nets. We sought to analyse whether biotic (seagrass shoot density, leaf length and meadow cover) and abiotic (sediment composition and particle size) structural elements explained variation in patterns of abundance and biomass. Underwater visual counts registered a larger abundance of individuals and proved significant variation in fish abundance and biomass at the scale of locations, which was otherwise not detected through seine nets. Seasonal variation in fish abundance and biomass was, in all cases, minor. Habitat structural elements helped to explain patterns in fish abundance and biomass. This fish species was particularly abundant in sediments dominated by coarse sands in continuous meadows of C. nodosa (>90% seagrass cover) with intermediate densities of 500 to 1000 shoots m -2 , followed by large-sized seagrass patches with >1000 shoots m -2 . A trade-off between protection provided by seagrass canopies and protection derived from its burial behaviour, limited under high seagrass shoot densities, may explain spatial variation patterns.Keywords: habitat; structural complexity; soft bottoms; sediments; sex ratio. Estructura poblacional del 'pejepeine', Xyrichtys novacula (Actinopterygii: Labridae), en mosaicos arena-pradera de fanerógama marina: variación espacial de acuerdo con las características del hábitat y técnicas de muestreo Resumen: La estructura del hábitat afecta a la distribución de los peces, particularmente en los hábitats dominados por arrecifes. Sin embargo, los estudios que conectan patrones de abundancia de peces en fondos blandos con la estructura del hábitat son, comparativamente, más escasos. En este estudio, se describen los patrones espacio-temporales de variación en abundancia, biomasa y estructura poblacional del 'pejepeine', Xyrichtys novacula, en hábitats de arena y praderas de faneró-gamas marinas constituidas por Cymodocea nodosa, empleando dos técnicas complementarias: censos visuales subacuáticos (UVCs) y arrastres (SNs). Se analizó si los elementos estructurales bióticos (densidad de pies, longitud de hoja y cobertura de la pradera) y abióticos (composición del sedimento y tamaño de las partículas) contribuyen a explicar la variación en los patrones de abundancia y biomasa. Los UVCs registraron una mayor abundancia de individuos y demostraron una variación significativa en abundancia y biomasa a escala de localidades, estas variaciones no fueron detectadas por los arrastres. La variación estacional en la abundancia y biomasa de individuos fue mínima en todos los casos. Los elemento...

High-Throughput Tracking of Social Networks in Marine Fish Populations

“…Marconato et al (1995) and Shen and Clark (2016) described the haremlike social structure of this species, where males were observed encompassing the smaller sub-territories of two to six females. The male:female proportion of individuals included in the study (1:1.93) was similar to the ratio described for this species using underwater visual censuses (1:85, Espino et al, 2015), but higher than the ratio obtained by the same authors using trawls (1:4.9). This suggests that males could be overrepresented in our dataset, probably because they are more susceptible to be fished due to their territorial behavior.…”

Aggressiveness-related behavioural types in the pearly razorfish

“…In general, it has been found that aggressiveness plays an important role in social structure, where the most aggressive males have a higher position in the mating hierarchy ( McGhee & Travis, 2010 ). This could be the case of the pearly razorfish, a species that lives in harems formed by a male and several females ( Espino et al, 2015 ) and where there is intra-sexual but not inter-sexual competition. Male and female territories usually overlap, suggesting that the shared space is used for reproduction ( Shen & Clark, 2016 ).…”

Peer Review #2 of "Aggressiveness-related behavioural types in the pearly razorfish (v0.1)"

“…In general, it has been found that aggressiveness plays an important role in social structure, where the most aggressive males have a higher position in the mating hierarchy (McGhee & Travis, 2010). This could be the case of the pearly razorfish, a species that lives in harems formed by a male and several females (Espino et al, 2015) and where there is intrasexual but not between-sexes competition. Male and female territories usually overlap, suggesting that the shared space is used for reproduction (Shen & Clark, 2016).…”