Feeding ecology, population structure and distribution of Pomatoschistus microps (Krøyer, 1838) and Pomatoschistus minutus (Pallas, 1770) in a temperate estuary, Portugal

Abstract

The feeding ecology, growth and spatialetemporal abundance and distribution of Pomatoschistus microps (Krøyer, 1838) and Pomatoschistus minutus (Pallas, 1770) were studied between June 2003 and June 2004, based on beam trawl surveys and macrobenthic samples conducted in the Mondego estuary, Portugal. Polychaetes, molluscs and amphipods were the most important items in the diet of P. microps, while for P. minutus the dominant preys were polychaetes, mysids and decapods. Pomatoschistus microps' recruitment lasted for six months and was composed of three new cohorts per year. Pomatoschistus minutus had an uncommon long reproductive season, from April to November, and population segregation was found, corresponding to the two reproductive peaks. Populations of both species were composed mainly of 0-group individuals with sand gobies presenting a more extended life span. In the Mondego estuary, inter-and intra-specific spatial segregation occurred between the two species and between the 0C and 1C age groups of P. microps. Ó 2005 Elsevier Ltd. All rights reserved.Keywords: Pomatoschistus; diet overlap; life cycle; competition; resource partitioning; Mondego estuary IntroductionHigh fish abundance concentrated in particular areas, is a common feature in estuarine fish communities (Elliott et al., 2002). Consequently, co-occurrence of several similar morphological types (e.g. species of Soleidae, Mugilidae, Gobiidae) with overlap of ecological niches within the communities is expected. Spatial and temporal distribution, abundance patterns of fish assemblages as well as resource partitioning, are therefore, important and interesting issues for understanding the structure and dynamics of these communities (Cabral, 2000). Competition exists when the requirements of two or more individuals for a particular resource exceed the supply of that resource in the environment; or, if their demands do not exceed the supply, but they compete directly to obtain this resource. The study of diet is often used to evaluate competition between fish species (Elliott et al., 2002).Trophic and habitat segregation are among the most important aspects of resource partitioning in fish communities but it has been difficult to assess and prove the main force behind this process (Ross, 1986a). Evidences of coexistent Gobiidae species exhibiting vertical spatial segregation, temporal segregation in spawning and absence of niche shifts when one species was temporarily absent have been reported by NorteCampos and Temming (1994). The Gobiidae is a particularly successful family in both tropical and temperate seas, well represented in estuarine and freshwater environments. Gobiidae present more than 2000 species (Bouchereau and Guelorget, 1998) and virtually all gobies exhibit demersal eggs, male parental care and highly variable number of spawnings per season (Miller, 1984).In the Mondego estuary, four species of Gobiidae are present: Pomatoschistus microps (Krøyer, 1838), Pomatoschistus and Miller, 1966). Although it is usually an annual spe...

The influence of an extreme drought event in the fish community of a southern Europe temperate estuary

“…In terms of numbers, the fish community was dominated by Pomatoschistus microps. This estuarine residents (ER) were the most abundant since the autumn of 2004, and in agreement with Leitão et al (2006), tend to occupy inner areas of the estuary, thus reducing competition with other Gobiidae species such as Pomatoschistus minutus, which is mainly concentrated at the mouth of the estuary (Leitão et al, 2006;. One significant aspect of this work was the reappearance of Symphodus bailloni, a marine species that lives in association Table 2 Mondego Estuary fish community: distribution of species according to Family and ecological guild (CA e catadromous adventitious species; ER e estuarine residents; MA e marine adventitious species; FW e freshwater adventitious species; MJ e marine juvenile migrant species; and NU e nursery species) and average number of individuals per 1000 m 2 for all the study periods CA e catadromous adventitious species; ER e estuarine residents; MA e marine adventitious species; FW e freshwater adventitious species; MJ e marine juvenile migrant species; and NU e nursery species.…”

“…Previous works regarding the Mondego Estuary fish community focused mainly on the structure according to the ecological guilds previously referenced and also on the importance of the estuary as a nursery area for commercial marine species (for further details see Jorge et al, 2002;Leitão et al, 2006Leitão et al, , 2007Martinho et al, 2007). As a general trend, in the last 15 years a major decline in species number from 1989e1992 to 2003/2004 was noticed, mostly freshwater species .…”

Estuarine production of resident and nursery fish species: Conditioning by drought events?

“…Several of the marine juvenile fishes that occur in estuaries are commercially important, hence estuaries may be considered as essential ecosystems for the renewal of fisheries resources, acquiring also a direct relevant economic value for mankind (Houde and Rutherford, 1993;Cowley and Whitfield, 2002;Able, 2005;Nicolas et al, 2007). Regarding resident species, their role as intermediates in the estuarine food web turns them crucial for the overall dynamics and functioning of the estuarine system (Leitão et al, 2006;Dolbeth et al, 2007a). Yet, estuarine areas are highly affected by human activities such as habitat reclamation, water quality impoverishment and fishing activities Vasconcelos et al, 2007) and are known for their high natural environmental variability (Maes et al, 2004;Elliott and Quintino, 2007).…”

Is <em>Fundulus heteroclitus</em> Intrusion Depleting Winter Marsh Pools of Native Fish Species?

“…Most important prey items in their diet are polychaetes, mysids, isopods and decapods [22]. Mummichog is also an opportunistic species but omnivore.…”

“…European salt marshes [6,18,21], and are particularly successful in temperate estuarine environments [22]. The mummichog was introduced in southwestern Iberian Peninsula in 1970's apparently due to cross-contamination of ballast water of ships coming from the USA [23].…”