Life History,Reproduction, Growth,Population Dynamics and Production of Gammarus aequicauda (Crustacea: Amphipoda) at Extremely Low Salinities in a Mediterranean Lagoon

Aspects of the biology of Gammarus aequicauda were studied at extremely low salinities (0.3–5.7 psu) in Monolimni Lagoon, N. Aegean Sea. Samples were collected monthly from February 1998 to February 1999. Breeding occurred continuously but peaked in late spring, late summer and autumn and three cohorts were produced. The spring and summer cohorts showed fast growth (0.15 mm d^–1), accelerated maturity and life span of about three and seven months respectively, while the overwintering cohort showed a life span of about nine months. The largest individual had a body length of 23.6 mm. Mean brood size was 54.5 early embryos, while the intramarsupial loss was 46%. Population density sharply increased in late spring, summer and autumn. Secondary production calculated by Hynes' method gave a mean annual density of 1077.4 ind. m^–2, a mean annual crop (B) of 2.93 g DW m^–2, an annual production (P) of 35.03 g DW m^–2 and a P: B ratio of 11.96. Gammarus aequicauda showed a life‐history pattern similar to those previously reported for this species at higher salinity environments with comparatively large final body length and high growth rate during summer, brood size and P: B ratio, but with high embryo loss as well. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Seasonal Variation of the Macrozoobenthic Community Structure at Low Salinities in a Mediterranean Lagoon (Monolimni Lagoon,Northern Aegean)

The macrozoobenthic community structure and dynamics at low salinities (0.3–6 psu) in a Mediterranean lagoon (Monolimni lagoon) were investigated. Samples were collected monthly from February 1998 to February 1999 at two sampling stations. Community structure was analyzed by means of uni‐ and multivariate methods. 21 taxa were collected; the amphipod Corophium orientale and the gastropod Ventrosia maritima dominated the assemblages. Total abundance peaked (50,000–60,000 individuals m^–2) in mid or late autumn. Community structure showed an almost even seasonal periodicity; seasonal changes were mainly derived from the intense variation in abundance of most species and the non–occurrence of a few ones (e.g. Corophium insidiosum, Polydora ciliata) in spring and summer. Non– occurrence, which led to a depression of the most diversity indices, was possibly the only direct impact of the extremely low salinities (~0.3 psu) on community structure. The main structuring factors of the community in the deeper outer part of the lagoon were water temperature and depth, and in the innermost part, where a Ruppia maritima meadow occurred, were water temperature and predation pressure by crabs (Carcinus aestuarii) and gobies (Knipowitchia caucasica). A temporary decline in total abundance in summer followed an increase in abundance of these predators. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Life history, aspects of reproductive biology and production of Corophium orientale (Crustacea: Amphipoda) in Monolimni lagoon (Evros Delta, North Aegean Sea)

Monthly samples of Corophium orientale were collected during February 1998–February 1999 in both parts of Monolimni lagoon (0.3 < Sal. < 6 psu, 2 < Temp. < 28.5 °C). Corophium orientaleshowed a semiannual life cycle. In the southern part, breeding occurred from early spring to mid autumn having three peaks, in early spring, early summer and early autumn, and three cohorts were produced, a spring cohort, a summer cohort and an overwintering one. In the shallower innermost northern part of Monolimni lagoon, breeding peaked in mid-spring and, also, in early autumn, and two discrete cohorts, a spring and an overwintering one, were produced. A lack of large individuals, attributed to a temporary size – selective predation by migrating shorebirds, was observed during summer. That lack possibly contributed to the hiatus in reproduction. Photoperiod seemed to be a more important cue than temperature in the initiation of the reproductive cycle, while extremely low salinities (<1 psu) did not deter breeding. Females attained maturity at a smaller size in late spring and, especially, in summer than in early spring at lower temperatures. Brood size was a function of females body size. Females, matured during summer at high temperatures, showed the lowest brood size, body length ratio. Mean brood size was small (12–13 early embryos) and embryo loss during development high (54%), possibly due to a negative effect of low salinities. A 1:1 sex ratio existed in the small body length classes, but females preponderated in the large ones. The spring cohort in the southern part, which developed at moderate temperatures, showed the highest growth rate (40 m day^–1). Secondary production of C. orientalecalculated by Hyness method gave a mean annual density of 4562.5 and 9327.6 ind. m^–2, a mean annual crop (B) of 1.03 and 2.67 g DW m^–2, an annual production (P) of 6.91 and 22.54 g DW m^–2 and a P/B ratio of 6.7 and 8.4 in the northern and southern part of the lagoon, respectively.     

Macrozoobenthic community structure in a poikilohaline Mediterranean lagoon (Laki Lagoon, northern Aegean)

The community structure of the macrobenthic fauna was studied in the overall area of Laki Lagoon in September 1997 (salinity 32–35 psu) and monthly from February 1998 to February 1999 in the innermost part of the lagoon (salinity 0.1–6.8 psu). Community structure was analyzed by means of uni- and multivariate methods. In September 1997, the macrofauna in the outer part of the lagoon was characterized by a higher diversity and the occurrence of both lagoonal and marine species, and in the innermost part by a higher total abundance and the occurrence of a few lagoonal species. The combination of distance from the sea, depth, salinity and sediment organic matter correlated best with the spatial distribution pattern of the macrobenthic fauna. Community structure in the innermost part of the lagoon showed a seasonal periodicity. Species composition during spring 1998, at 0.1–2.0 psu, was similar to that in September 1997. During summer the macrobenthic fauna became impoverished, but recovered from late summer onwards. The salinity increase during summer (up to 5–7 psu) was followed by the appearance of marine species in the innermost part of the lagoon. Total abundance displayed a peak in late spring and a lower one in mid-autumn. The seasonal dynamics of the faunal assemblage was mainly governed by water temperature. Predation pressure by Atherina boyeri may have contributed to quantitative community changes during autumn.     

Effects of salinity,light intensity and sediment on growth,pigments, agar production and reproduction in Gracilaria tenuistipitata from Songkhla Lagoon in Thailand

The effects of salinity, light intensity and sediment on Gracilaria tenuistipitata C.F. Chang & B.M. Xia on growth, pigments, agar production, and net photosynthesis rate were examined in the laboratory under varying conditions of salinity (0, 25 and 33 psu), light intensity (150, 400, 700 and 1000 µmol photons m^?2 s^?1) and sediment (0, 0.67 and 2.28 mg L^?1). These conditions simulated field conditions, to gain some understanding of the best conditions for cultivation of G. tenuistipitata. The highest growth rate was at 25 psu, 700 µmol photons m^?2 s^?1 with no sediments, that provided a 6.7% increase in weight gain. The highest agar production (24.8 ± 3.0 %DW) was at 25 psu, 150–400 µmol photons m^?2 s^?1 and no sediment. The highest pigment contents were phycoerythrin (0.8 ± 0.5 mg g^?1FW) and phycocyanin (0.34 ± 0.05 mg g^?1 FW) produced in low light conditions, at 150 µmol photons m^?2 s^?1. The highest photosynthesis rate was 161.3 ± 32.7 mg O₂ g^?1 DW h^?1 in 25 psu, 400 µmol photons m^?2 s^?1 without sediment in the short period of cultivation, (3 days) and 60.3 ± 6.7 mg O₂ g^?1 DW h^?1 in 25 psu, 700 µmol photons m^?2 s^?1 without sediment in the long period of cultivation (20 days). The results indicated that salinity was the most crucial factor affecting G. tenuistipitata growth and production. This would help to promote the cultivation of Gracilaria cultivation back into the lagoon using these now determined baseline conditions. Extrapolation of the results from the laboratory study to field conditions indicated that it was possible to obtain two crops of Gracilaria a year in the lagoon, with good yields of agar, from mid‐January to the end of April (dry season), and from mid‐July to the end of September (first rainy season) when provided sediment was restricted.     

Abundance,Population Structure and Production of Scrobicularia plana and Abra tenuis (Bivalvia: Scrobicularidae) in a Mediterranean Brackish Lagoon,Lake Ichkeul,Tunisia

Abundance, growth and production of the deposit‐feeding bivalves were studied in the Ichkeul wetland, northern Tunisia, from July 1993 – April 1994. Scrobicularia plana (Da Costa , 1778) occurred at annual mean densities (biomasses) of 299 ± 65 to 400 ± 100 individuals/m² (22.54 ± 3.00 to 34.27 ± 3.96 g ash‐free dry mass (AFDM)/m²) depending on the study area. The annual mean density of Abra tenuis (Montagu , 1803) amounted to 640 ± 74 individuals/m² during the whole study period, in contrast the biomass rose from 2.87 g AFDM/m² in July to 10.29 g AFDM/m² in April. Both species were largely dominated by age class I. Although not very successful, recruitment presented a two‐period pattern: the main period at the beginning of spring, and a secondary one in late summer/autumn. S. plana rarely exceeded 40 mm and lived for only 2 years, while most individuals of A. tenuis lived for only 15–18 months growing to a length of 12 mm. The annual bivalve deposit‐feeder production for the whole lagoon system (90 km²) was 8.24 g AFDM/m² (5.26 g C/m², 0.65 g N/m²). The annual P/ ratio was about 0.4 and therefore in the same order of magnitude as estimates from other brackish coastal waters. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Life History and Occurrence of Sialis lutaria L. (Megaloptera) in the Littoral Zone of Lake Esrom,Denmark

The life history and distribution of Sialis lutaria L. in the exposed littoral zone of Lake Esrom, Denmark were examined during 1979/80. Sialis showed an annual life cycle with mean annual abundance of 20 and 40 ind m⁻² at 0.4 and 2.0 m depth, respectively. Growth peaked during July with rates of about 10 % d⁻¹. Net annual production averaged 0.2 g DW at 0.4 m depth and 0.8 g DW at 2.0 m depth. The annual P/B-ratios were estimated in the range of 4.6-7.1.     

Life cycle,population dynamics,growth and production of <Emphasis Type="Italic">Abra segmentum</Emphasis> (Mollusca,Bivalvia) at low salinities in a Mediterranean lagoon

Aspects of the biology of Abra segmentum were investigated at low salinities in a Mediterranean coastal lagoon (Monolimni Lagoon, Northern Aegean Sea). Monthly samples were collected during the period from February 1998 to January 1999. Recruitment occurred from mid-spring to early autumn (0.3–5.7 psu) and recruits grew during summer and autumn (1.2–5.7 psu), while a major part vanished during next autumn, displaying a maximum life span of about 20 months. A positive correlation was found between the percentage of individuals having a shell length of ≤3.5 mm and temperature; age group 0 showed a growth rate of 0.97 mm per month, and the largest individual collected had a 19.76 mm shell length. The population density sharply increased during late spring (0.3–1.2 psu); this increase was followed by a decline during summer and, afterwards, a gradual increase up to late autumn. Secondary production calculated by the size–frequency method gave a mean annual density (n) of 3,357 individuals m⁻², a mean annual biomass (B) of 21.98 g DW m⁻², an annual production (P) of 73.72 g DW m⁻² and a P:B ratio of 3.35. A comparison of the present data with available data of A. segmentum populations from higher salinity habitats revealed that this bivalve in the study area showed a life history pattern similar to that of other populations of the species and a comparatively high growth rate, maximum body size, n, B, P and P:B ratio. Our findings suggest that the studied aspects of A. segmentum biology could not be markedly affected by low salinities.     

Macrobenthos ofPotamogeton andMyriophyllum beds in the upper reaches of Canal de Mira (Ria de Aveiro,NW Portugal): Community structure and environmental factors

The community structure of the macrobenthic fauna (>0.5 mm) ofPotamogeton andMyriophyllum beds of the upper reaches of Canal de Mira (0.5–2) and of macrofauna density (369, 240 ind m^–2).Potamopyrgus jenkinsi, Corophium multisetosum andLimnodrilus hoffmeisteri are dominant species in the study area. The community of station 1 includes an important set of taxa usually associated to freshwater habitats (oligochaetes, leeches and insect larvae) whilst in station 3 typically estuarine species (Cyathura carinata, Leptocheirus pilosus, Nereis diversicolor, Streblospio shrubsolii) occur. A succession of peak densities of different taxonomic groups during the year indicates seasonal variation in the community structure. The faunal assemblage of the study area is compared with similar ones in NE Atlantic and Mediterranean coastal systems.     

Biodiversity and distribution of polychaetes and molluscs along the Dese estuary (Lagoon of Venice, Italy)

Mollusc and polychaete distribution in the mud flats along the Dese estuary (lagoon of Venice, Italy) was analysed in May, August and October to evaluate taxonomic biodiversity and zonation pattern of soft macrobenthos in an area of the lagoon hardly known from this point of view. Throughout the studied area most of the species were polychaetes, particularly Streblospio shrubsolii (Buchanan), which showed greater abundance from May to October. Molluscs and polychaetes showed a zonation of marine species which colonize brackish environments in the outer and intermediate areas of the estuary and of brackish water species in the inner one. In the outer area different assemblages were attributed to different sediment types. This distribution pattern, put in relation to the distance from the sea, was evident in May and partly blurred in August and October: the assemblages of the inner area of the estuary invaded the intermediated area in August and affected outer area in October because of spreading of the brackish water species S. shrubsolii, which became dominant. The distribution pattern of molluscs and polychaetes can be explained in terms of confinement as the leading factor influencing water quality and dynamics of the ecosystem. It is also needed to be taken into consideration the role played by competition due to different degree of opportunism of the most abundant species.     

Population Dynamics,Growth and Productivity of Abra ovata (Mollusca,Bivalvia) in the Evros Delta (North Aegean Sea)

Monthly samples of Abra ovata were collected during February 1983-January 1984 in the Evros Delta (N. Aegean Sea). Population density (mean annual value = 2407.5 ind · m⁻²) was characterized by seasonal variation. An analysis of the length frequency distributions shows that one annual recruitment of juveniles (> 2 mm) occurred in October-January; and also that, throughout the year, two age groups existed in the population. One growth ring was formed on the shells of the oldest age group during July-August. Mean growth in shell length can be described by Bertalanffy function. A positive correlation existed between shell length and decalcified dry weight. Secondary production in A. ovata, calculated by the instantaneous growth method, showed a mean biomass of 29.221 g dry weight m⁻²yr⁻¹, a productivity of 17.086 g dry weight m⁻²yr⁻¹ and an annual turnover ratio of 0.59.     

Life cycle and growth ofTrichostegia minor (Curtis) in temporary woodland pools (Trichoptera: Phryganeidae)

Larvae of the caddisTrichostegia minor (Curtis) were collected from four woodland pools in The Netherlands, three of which are temporary, from August 1986 till June 1987. Eggs and larvae of this species proved to be very well adapted to drought, freezing, strongly fluctuating pH and alkalinity levels and prolonged oxygen deficit. The life cycle ofT.minor in a small woodland marsh overgrown byCalla palustris took one year. Adult flight period started at the end of May. Oviposition took place independent of water. Hatching of the eggs started in September and was probably induced by immersion. During the larval stage from September until May, 5 instars could be distinguished by the size of the head capsule. Growth of instars I, II and III during autumn was moderate. Most larvae overwintered as instar III or IV. Possibly there was a larval diapause during winter. In spring rapid growth to instar V took place prior to pupation. Growth rate, expressed as the increase of mean individual dry weight was highest from March to April (2.05±0.75% DW.m^–2.d^–1). In extremely shallow water growth in spring was initially more rapid compared to growth in deeper water. During winter the growth rate decreased to 0.038±0.071% DW.m^–2.d^–1. Net annual production based on the changes of momentary biomass was 183.2±31.7 mg DW.m^–2.y^–1 or 177.2±31.3 mg AFDW.m^–2.y^–1. Production loss during the winter season was 75.1±10.8 mg DW.m^–2.y^–1 or 72.3±10.6 mg AFDW.m^–2.y^–1.     

Population dynamics, growth and reproduction of Corophium insidiosum (Crustacea: Amphipoda) at low salinities in Monolimni lagoon (Evros Delta, North Aegean Sea)

Distribution, population dynamics, growth and aspects of reproductive biology of Corophium insidiosum were investigated in Monolimni lagoon. Samples were collected in July 1997 (at 30 psu S) and during February 1998–May 1999 (at 0.1–5.7 psu S). Corophium insidiosumwas almost exclusively found in the outer part of the lagoon, which showed a higher water renewal rate. Population density gradually decreased during winter and spring, when salinity was lower than 1 psu and the amphipod finally vanished from the lagoon. Salinity increase during summer (1.2–5.7 psu) was followed by the re-occurrence of C. insidiosum with a time lag of 2–3 months. Population density increased in autumn and peaked in early winter at salinities 1.6–4.2 psu. Three cohorts appeared in the population during September 1998–March 1999. Breeding activity peaked in early autumn (14–21?°C, 4 psu S) and ceased after December (2–6.5?°C, ¡1.5 psu S). The preponderance of females in the large size classes resulted in a female- biased sex ratio in the whole population. The population showed a growth rate of 7.5–11.2 μm d^?1 being faster in autumn (9–21?°C, 3–4 psu S) than in winter (2–12?°C, 0.2–3 psu). An exponential relation existed between body length and cephalic length or dry body weight, while brood size was directly related to body length. Mean brood size was small (4.96 early embryos) and egg loss during development high (53%), possibly as a consequence of low salinities.     

Distribution and production ofChironomus salinarius (Diptera: Chironomidae) in a shallow coastal lagoon in the Bay of Cádiz

The abundance, generation time and production ofChironomus salinarius larvae in a lagoon fish-pond system in the Bay of Cádiz were studied by taking monthly samples at 3 sites during 1991 and 1992. Numerical abundance and biomass of larvae showed considerable spatial, seasonal and interannual variation (ANCOVAs,P<0.001). The maximum mean annual density was 7048 larvae m^–2, and corresponded to a biomass of 3.08 g dry weight (DW) m^–2. It was recorded at the site with the lowest rate of water renewal. Seasonal patterns were similar at all sites, with main annual peaks of abundance and biomass in autumn-early winter. Chironomid density was positively related to the biomass of benthic macroalgae (P<0.001). The population studied was multivoltine with a probable average of five generations per year, with overlapping cohorts and a predominance of third- and fourth-instar larvae. Estimates of annual production ranged between 72.2 g DW m^–2 yr^–1 at the site with the lowest rate of water renewal in 1991 and 0.1 g DW m^–2 yr^–1 at the site with the highest rate of water renewal in 1992. Mean annual production and the production/biomass ratio for the system was estimated to be 16.8 g DW m^–2 yr^–1 and 12.7, respectively. Possible factors leading to the observed density fluctuations are discussed, as well as possible sources of error in production estimates.     

Effects of Submerged Aquatic Vegetation on Macrozoobenthos in a Coastal Lagoon of the Southwestern Atlantic

The freshwater‐dominated part of Rocha coastal lagoon recently experienced sudden colonization by submerged aquatic vegetation (SAV). Macrophytes may be beneficial or detrimental for the zoobenthos, and both assemblages may in turn affect the food availability for birds and fishes. With the aim of evaluating the effect of SAV on water conditions and on the composition, abundance and diversity of macrozoobenthos, vegetated areas (V, up to 500 g DW m^–2) were compared with vegetation‐free areas (N). The benthic abundance was higher in V (up to 5000 ind m^–2) than in N (up to 2200 ind m^–2). Species richness and abundance of amphipods, gastropods and chironomids were also higher at V compared with N. Conversely, the abundance of Tanais stanfordi (Crustacea), Erodona mactroides (Bivalvia) and Laeonereis culveri (Polychaeta), and the Shannon diversity were higher at N. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Population dynamics and production of the tropical freshwater shrimp Caridina nilotica (Decapoda: Atyidae) in the littoral of Lake Sibaya

SUMMARY. Seasonal changes in population structure, standing stock levels and production of Caridina nilotica were studied at three sites in the littoral margins of subtropical Lake Sibaya between January 1975 and March 1976. Average population density at these sites declined from a maximum of c. 1400 to a minimum of c. 350 individuals per m² (3.4–0.4 g m^?2 dry wt) during the study, possibly as a result of emigration into peripheral vegetation inundated by rising lake levels. Shrimps bred perennially and, although egg stocks and instantaneous birth rates (b) were highest during summer, no corresponding increases in populaton density were observed, suggesting that the seasonally higher birth rates were offset by higher mortality rates. Population size structure and size-specific sex ratios did not change seasonally to any marked extent. Relative abundance declined with size and females grew larger than males. Clutch size increased linearly as a function of female carapace length. Estimates of overall mean annual somatic production (g m^?2 year^?1 dry wt) for the three sites between January 1975 and January 1976 ranged between c. 132 (egg-ratio method), 37.5 (summation of growth increments) and 24 (Hynes-Hamilton method) at an annual mean standing stock level of 2.7 g m^?2 dry wt (calorific value, 20.34 kJ g^?1 dry wt). Production at sites 1, 2 and 3 decreased in line with declining annual mean standing stocks (5.32, 3.67 and 0.23 g m^?2, respectively). The growth increment method gave an overall mean annual P/B value of 13.9. Egg production amounted to a further 5.6, 3.6 and 0.1 g m^?2 year^?1 dry wt (calorific value, 28.01 kJ g^?1) at sites 1, 2 and 3, or 2.7 g m^?2 year^?1 on average.     

The distribution,growth, and reproduction of the Antarctic limpet Nacella (Patinigera) concinna (Strebel, 1908)

Twenty-one monthly collections of the Antarctic limpet Nacella (Patinigera) concinna (Strebel, 1908) were obtained by divers at Signy Island, South Orkney Islands. A mean monthly population density of 123.7 ± 21.2 · m^?2, mean biomass of 13.7 ± 2.7 g dry tissue wt · m^?2, and annual production of 2.9 g · m^?2 were recorded in the depth range 2–12 m below mean low water.Shell growth was slow with a maximum growth rate, in the first 3–5 yr of life, of 3 4 mm per year. Maturity was attained at 7–8 yr (21 mm length), and maximum size (41 mm length) at about 21 yr. Unique spawning behaviour was observed in two Austral springs, and data relating spawning to the spring increase in sea temperature were obtained.     

Numbers and biomass of centipedes (Lithobiomorpha: Chilopoda) in a Betula-Alnus woodland in N.E. England

Summary Over a period of 1 year the mean monthly population densities of L. forficatus varied between 7.58 m^-2 (February) and 24.07 m^-2 (October). The equivalent values for L. crassipes were 17.05 m^-2 (February) and 64.17 m^-2 (October). The annual mean population density of the two species was estimated at 51 m^-2 with a biomass of 0.585 g live wt m^-2. Less than 4% of the total lithobiid population was found in decaying logs and tree stumps, most of the population inhabited the soil/litter layers.Seasonal fluctuation in numbers was shown to be unimodal in L. forficatus and bimodal in L. crassipes. A similar pattern was noted in the status of the ovaries, L. forficatus appears to have a single peak breeding period (September) while L. crassipes has two (June and September).In terms of biomass, the relative importance of centipedes among other woodland invertebrate predators is high.     

Seasonal variability of secondary production of cladocerans and rotifers,and their trophic role in Lake Tana,Ethiopia, a large,turbid, tropical highland lake

Daily and annual production rates of eight cladoceran and two rotifer species, and their seasonal variation and trophic role in the large, turbid, tropical Lake Tana, Ethiopia, were assessed in 2003–2005. Laboratory cultures were used to infer cladoceran development times, and secondary production was estimated using the growth increment summation and recruitment methods. Production for both taxa was highest in October–November, after the rainy season, and lowest in January–April during the dry season. Cladocerans and rotifers comprised 24% of the metazoan zooplankton biomass of 45.1 mg DW m^?3, but comprised 53% of its production. Daily production for cladocerans and rotifers, respectively, was 1.23 and 0.94 mg DW m^?3 d^?1, and annual production was 447.9 and 353.5 mg DW m^?3 y^?1. Energy transfer efficiency from producers to zooplankton was 1.3% and 4.4% from zooplankton to planktivores. Herbivores consumed 3.4% of primary production and planktivores 36% of zooplankton production. High biomass turnover rates of cladocerans and rotifers sustain planktivores and, after a month's delay, decomposed Microcystis provides their main food source during the pre- and post-rainy months in Lake Tana.     

Life history and secondary production of Electrogena ujhelyii (Ephemeroptera: Heptageniidae) in a small forest stream in West Carpathians

In this study we focused on life history parameters of Electrogena ujhelyii. We studied life cycle, nymphal growth pattern, biomass and secondary production in a small, calcareous stream in Malé Karpaty Mts (West Carpathians). The life cycle was univoltine with a large range in the size of nymphs during most samples dates. Mean annual density was 40 ind. m^?2 and the annual secondary production reached 183 mg DW m^?2 y^?1. There are no published data available on the secondary production values of this species, therefore these are the first published data.