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Length-weight relationships (LWRs) for six fish species caught from tidepools in an intertidal rocky shore in the Gulf of Cadiz are presented. This study presents the first data on LWR for Clinitrachus argentatus (WT = 0.0069 * TL3.077), Coryphoblennius galerita (WT = 0.0051 * TL3.409), and Parablennius incognitus (WT = 0.0090 * TL3.113) outside the Mediterranean Sea and adjacent eastern waters. The data of LWRs for juveniles of Symphodus roissali (WT = 0.0117 * TL3.091), Serranus scriba (WT = 0.0165 * TL2.881), and Diplodus cervinus (WT = 0.0152 * TL3.060) are also presented for first-time. Due to fish body shape may vary during growth in relation to size, studies covering a specific size range relating to life stage can be useful to estimate the LWRs for different development phases. The findings of this study fill the gap in LWRs data for immature fish in S. roissali, S. scriba and D. cervinus. Moreover, because intertidal zones and their adjacent subtidal areas represent nursery grounds for species that eventually recruit to coastal fisheries, the LWRs estimates for other species can also help to understand the population dynamics and conservation for native fish species.

The reproductive cycle of seven common species (Gobius paganellus, Gobius bucchichi, Gobius cobitis, Parablennius sanguinolentus, Salaria pavo, Tripterygion tartessicum and Symphodus roissali) on rocky shores in the Gulf of Cadiz and their relationship with the sea surface temperature (SST) is analysed. Partial data on Scorpaena porcus are also given. Fecundity of these short lifespan species shows a positive linear correlation between the number of oocytes and an increase in female size. Spawnings are concentrated in the first 7 months of the year. An analysis of reproductive growth with respect to SST shows that water temperature in the winter months affects the timing of the onset of reproduction in most species. Recruitment is takes place throughout the year, but a temporal segregation within different families occurs in their spawning as well as recruitment.

The present work on the feeding ecology of Scorpaena porcus according to season, sex and size, is the first study carried out in the rocky intertidal in the NE Atlantic. Previous studies were carried out with fish collected in fishing grounds from Mediterranean areas. A total of 106 fish were caught in monthly samplings from April 2008 to July 2010 in three areas of the rocky intertidal zone in the Gulf of Cadiz. The diet composition varied with season, size and sex. Shrimps were the main diet resource during all year, but other prey were also important depending on the season. As the size of fish increased, predation on smaller crustaceans decreased and consumption of larger crustaceans and fish augmented. Females and males based their diet on shrimps, while indeterminate fish fed largely on amphipods. No significant differences were found between feeding intensity and season, size and sex. Nevertheless, the PERMANOVA results showed that the number of prey is affected by the interaction between sex and size class. Our results highlight that S. porcus is a stenophagic species that shows a gradual segregation in the use of resources as it grows, which indicates there is no intraspecific competition in the rocky intertidal.

This paper describes the use of resources and diet of nine resident fish species in the rocky intertidal zone of the Gulf of Cadiz and examines whether their populations are affected by trophic competition. A stomach content analysis of the nine species revealed that only one was herbivorous ( Parablennius sanguinolentus ), while the rest were mainly carnivorous ( Gobius bucchichi , Gobius cobitis , Gobius paganellus , Zebrus zebrus , Salaria pavo , Lepadogaster lepadogaster , Scorpaena porcus and Tripterygion tripteronotum ). The most frequently consumed prey were amphipods, isopods, polychaetes, decapods, chironomids, tanaidaceans, gastropods, copepods, cumaceans and ostracods. In most species, the occurrence of polychaetes and molluscs was higher in the cold season, whereas that of isopods, decapods, chironomids and fish increased in the warm season. In general, larger specimens consumed larger prey, with an increase in the occurrence of isopods, decapods and fish. An analysis of trophic niche breadth defined G. cobitis as generalist, G. bucchichi as opportunist and S. porcus as specialist, whereas the values obtained for the other species did not indicate a clearly defined strategy. Low diet overlap values and the segregation observed in several analyses indicated an adequate distribution of resources.

Intertidal fish are adapted to live in a fluctuating environment and are considered suitable bioindicators of environmental change. Understanding the relationship between fish species distribution and environmental variables is fundamental for comparative analysis among geographical locations and identification of long-term trends predicted by global warming. Here we analysed a combination of the main micro- and macroscale factors that affect the distribution and abundance of rocky intertidal fish communities. Monthly sampling of fish assemblages at 3 sites in the rocky intertidal zone of the Gulf of Cadiz was conducted from 2008 to 2014. Fish assemblage descriptions were based on relative abundance, biomass, diversity and evenness. A canonical correspondence analysis was performed to evaluate the relationship between pool characteristics (substratum type, depth and surface area) and the abundance of fish assemblages in tidepools. The results showed differences between protected and unprotected sites, which may indicate that human pressure induces changes at all assemblage levels. At all sites, the lowest abundance was observed in the year with the greatest wave energy. The diversity at the 3 sites showed interannual variation correlated with pool complexity, wave energy and air temperature. These findings increase our understanding of the mechanisms that regulate the distribution of fish assemblages in shallow coastal waters and provide a useful baseline for future management and conservation of these areas.