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F. C. FÉLIX. ET AL.

Introduction It is academically accepted that fish assemblages of surf zones are numerically dominated by few species (McFarland 1963, Modde & Ross 1981) made up largely of juveniles with small body size (Robertson & Lenanton 1984, Lasiak 1986, Reina-Hervas & Serrano 1987, Gibson et al. 1996, Clark 1997). These characteristics are usually found in sheltered estuarine areas where the nursery function has been well established (Gibson 1973, Ruple 1984, Lasiak 1984, Ross et al. 1987). The high dynamics of surf zones may act as sheltered habitats and offer the same advantages of protection against predators and abundant food supply (McLachlan 1983, Ross 1983, Lasiak 1986, Bennet 1989) to marine fish. These features are provided by a continued wave action above the sandy floor, making nutrients available to marine food web (McLachlan 1980) and diminishing visibility due to increased turbidity

(Gibson 1973).

In

general,

highest

diversities

and

abundances are found in warmer months (Fox & Mack 1968, Naughton & Saloman 1978, Modde & Ross 1981, Ross 1983, Lasiak 1984), while small abundances are observed during winter months. Conversely, Godefroid (1996) and Monteiro-Neto et al. (1990), who worked on

sandy

beaches

in

Southern

Brazil,

found

that smallest abundances of fish occurred in spring. Many authors attributed the seasonal fluctuation of abundance to temperature, salinity, turbidity and wind velocity, with the latter factor being considered less important during long-period fluctuations and more determinant only in short-time changes (Modde & Ross 1981, Allen 1982, Ross et al. 1987, Lamberth et al. 1995). Seasonal cycles in fish abundance and diversity at beach surf zones can not be ascribed to changes in physical conditions, but rather to the reflex of recruitment patterns determined by reproductive activity and coastal circulation (Ross et al. 1987, Gibson et al. 1993, Lamberth et

1995), which

occur either

temporary

exploration

al. or

by of

adult emigration

adjacent

high

productivity areas (Allen 1982).

The

present

study

aimed

to

provide

detailed

biological

information

on

size

characterization fish inhabiting

and temporal utilization shallow habitats such

of as

sand beaches, and the particularities within each species.

Materials and methods Study site

The study took place at Pontal do Paraná, Paraná State, Southern Brazil. The sampled area is approximately 3 km long and is geographically protected by prevailing East-Southeasternly winds because of the presence of two islands (Mel Island and Galheta) and submerged sand bars built by the tidal regime of Paranaguá bay estuarine complex (Fig. 1). According to Godefroid (1996), the studied area is classified as dissipative with sediment grain size diminishing from the entrance of Paranaguá bay southwards. The beaches are microtidal (tidal range < 1.5 m) with two ebb tides per day. Local weather is classified as humid subtropical climate with warm summer and undefined dry season (Bigarella 1978, Angulo 1992). Precipitation reaches 1998 mm per year and summer is the rainy season.

Fish assemblages were sampled using a beach seine net, 15 m long and 2.6 m height with a stretched mesh size of 5 mm, at 3 locations. Samples were collected during daylight hours, between 6.00 and 10.00h from June 2004 to May 2005. Five hauls, each covering 30 m in distance, were made per site. Hauls were separated by 5m to minimize the influence between them, and all samples were collected at low water spring tides. The hauls were conducted by two people, one on each end of the net. The net was taken towards the surf zone by one of them to a depth of 1.5 m, approximately between 10 and 30 m into the sea. Both sides were pulled simultaneously parallel to the beach face up to 30 m, when the deeper end of the net was pulled towards the other net end.

All fish collected were identified to species level following Figueiredo & Menezes, 1978,

Figueiredo Figueiredo

& Menezes, , 1980, Meneze

1980, Menezes & s & Figueiredo, 1985,

Barletta & Corrêa, 1992, Figueiredo & Menezes, 2000. Specimens were weighted (g) and measured to the nearest 1 mm (total length and standard length), except when samples were very large. In such cases, measurements were restricted to a sub sample of 30 individuals per species. The remainder was weighted, counted and incorporated as weight and number counts. In addition, sex (male, female or non identified) and maturity stage were documented for the sub sample through direct observation, according to the macroscopic scale of gonadal maturation of Vazzoler (1981).

To verify the environmental influence on the faunal composition and structure at each site, surf zone water temperature (°C), salinity (Practical

Pan-American Journal of Aquatic Sciences (2007) 2 (1): 27-39

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