Asunción Andreu-Soler

Effects of Shoreline Urban Modification on Habitat Structure and Fish Community in Littoral Areas of a Mediterranean Coastal Lagoon (Mar Menor, Spain)

The shallow habitats of coastal lagoons play an invaluable role for fish communities as nursery areas and provide essential habitats for threatened fish species. Shoreline modification is an anthropogenic coastal stressor that can negatively affect aquatic communities through the modification of nearshore habitats. The aim of the present study was to quantify the effects of two types of shoreline conditions on habitat structure and fish community of littoral habitats. Unmodified shorelines adjacent to saltmarshes and recreational beaches in urbanised areas of the Mar Menor coastal lagoon were compared. The results showed that there were significant differences in habitat structure, fish community structure and fish species abundance by shoreline type. Recreational beaches were characterised by higher water depth and homogeneous substrata, while unmodified shorelines showed high substrata heterogeneity and supported well developed meadows of submerged vegetation. The latter shoreline type provided an important nursery habitat for marine species such as Sparus aurata and Liza saliens, and represented critical habitats for species of conservation concern such as Aphanius iberus and Syngnathus abaster. Littoral areas adjacent to modified shorelines were dominated by Pomatoschistus marmoratus. We suggest that urbanisation has impacted fish assemblages through degradation of habitat structure (loss of complexity and refuge areas).

Effects of Exotic Fishes on the Somatic Condition of the Endangered Killifish Fundulus lima (Teleostei: Fundulidae) in Oases of Baja California Sur, Mexico

Abstract We assessed the effects of the abundance and biomass of four exotic fishes (common carp, Cyprinus carpio; guppy, Poecilia reticulata; green swordtail, Xiphophorus hellerii; and redbelly tilapia, Tilapia cf. zillii) on the residual somatic condition (Kr) of endangered Baja California killifish (Fundulus lima) in two oasis systems of Baja California Sur, Mexico. We used multiple regressions to analyze relationships between Kr of the killifish and 21 ecological variables. Biomass of redbelly tilapia and common carp were variables that better explained variation in Kr among populations of killifish. In both drainages, redbelly tilapia was the dominant fish, which relegated smaller habitat units to the other coexisting species of fishes, increasing competition among them and decreasing Kr and abundance of the endemic killifish. We concluded that Kr for populations of killifish may be a good indicator of the competitive interactions with exotic fishes in drainages of Baja California peninsula and should be considered when such stocks are subject to recovery plans or any other management program. Resumen Evaluamos los efectos de la abundancia y biomasa de cuatro especies ícticas exóticas (carpa común, Cyprinus carpio; gupi, Poecilia reticulata; espadita verde, Xiphophorus hellerii; y la tilapia panza roja, Tilapia cf. zillii) sobre la condición somática residual (Kr) de la sardinilla peninsular en peligro de extinción (Fundulus lima) en dos sistemas de oasis de Baja California Sur, México. Utilizamos regresiones múltiples para analizar las relaciones entre el Kr de la sardinilla peninsular y 21 variables ecológicas, siendo las biomasas de la tilapia panza roja y la carpa común las variables que mejor explicaron la variación de Kr para las poblaciones de sardinilla peninsular. La tilapia panza roja fue la especie dominante en ambas cuencas, relegando a las otras especies ícticas coexistentes a ocupar unidades de hábitat más pequeñas, incrementando una mayor competencia entre ellas y reduciendo el Kr y la abundancia de la sardinilla peninsular. Concluimos que el Kr de las poblaciones de sardinilla peninsular puede ser un buen indicador de las interacciones competitivas con especies exóticas en las cuencas hidrológicas de la península de Baja California y podría ser considerado cuando tales poblaciones estén sujetas a planes de recuperación o cualquier otro programa de manejo.