Analysis of the cycle of reproduction of Sardina pilchardus (Walbaum, 1792) off the Moroccan Atlantic coast

This work focuses on aspects of reproductive biology of Sardina pilchardus from the Atlantic coast of Morocco. The mean values of batch fecundity estimated for the species is 23150(+/-1301) oocytes for a mean size of 19.5(+/-0.49) cm, the mean relative fecundity being 346(+/-7.34) oocytes per gram of female without ovary. Batch fecundity increases with total length and body weight without ovary. Sizes at first sexual maturity (L50) are reached for males and females at 15.8(+/-0.29) cm and 15.8(+/-0.35) cm, respectively. The spawning period for the population extends between October and July and the spawning peak occurs from October to February. However, the small sardines (14.5-17 cm) in their first reproduction spawn between November and June, whereas larger fish (17.5-25 cm) spawn between October and July. The factor of condition (K) increased in summer during the sexual resting phase. It is weak in winter during the period of reproduction. Regarding, the sex ratio, there was no significant difference in the number of males and females.     

Effects of suspended mussel culture on benthic-pelagic coupling in a coastal upwelling system (Ría de Vigo, NW Iberian Peninsula)

The influence of suspended mussel culture on the benthic-pelagic coupling was evaluated in the Ría de Vigo, in the coastal upwelling system of the NW Iberian Peninsula, during the month of July 2004. Measurements of water column properties were carried out at three stations in the Ría de Vigo: under a mussel raft (1), and at two reference sites in the main channel (2) and in the inner part (3) of the Ría. Dissolved nutrients, dissolved oxygen and inorganic carbon benthic fluxes were measured by means of a benthic chamber at stations 1 and 3. Sediment traps were deployed at 6 locations to estimate vertical fluxes. The water column structure at the three study stations was very similar, characterized by upwelling conditions during the second week of July and a posterior stratification showing a strong thermocline, with a depth fluctuation mainly modulated by the shelf wind regime. Vertical POC fluxes underneath the mussel raft (3 g C m⁻² d^− 1) were 3 times higher than those obtained between rafts and 10 times higher than in the main channel reference site. Dissolved oxygen, ammonium, silicate and phosphate benthic fluxes were significantly higher under the raft than at the inner Ría reference site. A 1D carbon budget showed the importance of benthic metabolism under the raft (2.3 ± 0.8 g C m^− 2 d^− 1), being higher than the organic carbon produced at the photic layer (0.7 ± 0.3 g C m^− 2 d^− 1), as a result of higher organic loading compared to the inner Ría reference site. The results show for the first time the important role that suspended mussel cultures play in the benthic-pelagic coupling in this coastal upwelling ecosystem.     

Dynamics of Black Band Disease in a <Emphasis Type=Italic>Diploria strigosa</Emphasis> population subjected to annual upwelling on the northeastern coast of Venezuela

Temporal variability of Black Band Disease (BBD) prevalence, incidence, recurrence, recovery and virulence was estimated in a Diploria strigosa population from an upwelling zone of Venezuela, for 1 year between August 2004 and August 2005. The sampling spanned both upwelling and non-upwelling seasons, and included three samplings, roughly 60 days apart, within each season. The negative effects of BBD epizootiology in the sampling population (El Mercado reef) were positively correlated with sea surface temperature (taken as an upwelling estimator). Disease prevalence, incidence and recurrence decreased significantly during upwelling, and the recovery rate increased. Contrary to expectations, tissue mortality did not decrease significantly during the upwelling season, remaining at 1.2 ± 0.7 mm day⁻¹. BBD prevalence, and the ensuing rates of tissue mortality were higher than values previously reported for other Caribbean reefs, even during upwelling episodes, suggesting that nutrient enrichment of the local waters by upwelling counteracts the expected reductions of the disease prevalence and virulence due to the lower temperature. Colonies which had previously been infected with BBD were up to six times more susceptible to new infections than those which were not infected during the preceding 7 months, suggesting that the infected colonies never healed completely. The high variability between tissue mortality values among coral colonies also suggests that overall host health-status may alter susceptibility to BBD infections.     

Organic-walled dinoflagellate cyst production in relation to upwelling intensity and lithogenic influx in the Cape Blanc region (off north-west Africa)

Fossil dinoflagellate cyst assemblages are increasingly used in paleoclimatic research to establish paleoenvi‐ronmental reconstructions. To obtain reliable reconstructions, it is essential to know which physical factors influence the cyst production. Most information about the relationship between variations in physical parameters and cyst production is known from middle and higher latitudes. Information from the (sub)tropics is rare. To increase this information, the temporal variation in cyst assemblages from the upwelling area off north‐west Africa (off Mauritania) has been compared to environmental conditions of the upper water column. Samples were collected by the sediment trap CB9, off north‐west Africa (Cape Blanc, 21°15′2″N, 20°42′2″W) between 11 June 1998 and 7 November 1999 at 27.5‐day intervals. Off Cape Blanc, upwelling occurs throughout the year with variable intensity. This region is also characterized by frequently occurring Saharan dust storms. Seasonal variations in dust input, upwelling intensity and sea surface temperature are reflected by the production of organic‐walled dinoflagellate cyst assemblages. Several cyst taxa are produced throughout the sampling interval, with the highest fluxes at times of strongest upwelling relaxation and/or dust input (Echinidinium aculeatum Zonneveld, Echini‐din ium delicatum Zonneveld, Echinidinium granulaturn Zonneveld, Echinidinium spp., Impagidinium aculeatum (Wall) Lentin et Williams, Impagidinium sphaeri‐cum (Wall) Lentin et Williams, Protoperidinium americanum (Gran et Braarud) Balech, Protoperidinium stellatum (Wall in Wall et Dale) Rochon etal., Protoperidinium spp., Selenopemphix nephroides (Benedek) Benedek et Sarjeant and Selenopemphix quanta (Bradford) Matsuoka). Species such as, for example, Bitectatodinium spongium (Zonneveld) Zonneveld et Jurkschat and Impagidinium patulum (Wall) Stover et Evitt do not show any production pattern related to a particular season of the year or to specific environmental conditions in the upper water column. The production of cysts of Protoperidinium monospinum (Paulsen) Zonneveld et Dale is restricted to intervals with increased nutrient concentrations in upper waters when sea surface temperatures at the sampling site is below approximately 24°C.     

Canine leishmaniasis in the Rif mountains (Moroccan Mediterranean coast): a seroepidemiological survey

A sero-epidemiological survey has been conducted in several localities of the province of Nador to investigate canine leishmaniasis in the North-Eastern slope of the Rif mountains (Mediterranean coast of Morocco). Serum samples collected from 257 dogs were analysed using indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA) to detect anti-Leishmania infantum antibodies. Forty eight (18.7%) of the screened dogs were IFAT positive and 54 (21.0%) were ELISA positive; the concordance of the two methods was 96.1%. The prevalence of infection is significantly higher in dogs more than four years of age whereas no significant difference in prevalence of infection was seen between males and females. The frequent symptoms observed in seropositive dogs were the enlargement of lymph nodes (57.4%), emaciation (51.9%) and skin involvement (25.9%). However, 38.9% of those dogs showed no one of the major symptoms of visceral leishmaniasis. Leishmania isolated from three of the examined dogs was identified as L. infantum MON-1. These results show that the North-Eastern slope of the Rif mountains is one of the most active Mediterranean areas of visceral leishmaniasis and confirm that the dog is the main reservoir of L. infantum.     

Seasonal variations in upwelling and in the grazing impact of copepods on phytoplankton off A Coruña (Galicia, NW Spain)

The impact of grazing by copepods on phytoplankton was studied during a seasonal cycle on the Galician shelf off A Coruña (NW Spain). Grazing was estimated by measuring the chlorophyll gut content and the evacuation rates of copepods from three mesh-size classes: 200-500 (small), 500-1000 (medium), and 1000-2000 μm (large). Between February 1996 and June 1997, monthly measurements of water temperature, chlorophyll concentration, primary production rates, and copepod abundance, chlorophyll gut content, and evacuation rates were taken at an 80-m-deep, fixed shelf station. Additionally, the same measurements were collected daily during two bloom events in March and in July 1996. Small copepods were the most abundant through the seasonal cycle. The highest grazing impact, however, was due to the medium and large size classes. Grazing by small copepods exceeded grazing by medium and large copepods only during phytoplankton spring blooms. The impact of copepod grazing (considering all size fractions) was generally low. On average, 2% of the phytoplankton biomass and 6% of the primary production were removed daily by the copepod community. Maximum grazing impact values (9% of the phytoplankton biomass and 39% of the primary production) were found in mid-summer. These results suggest that most of the phytoplankton biomass would escape direct copepod grazing in this upwelling area.     

Comparative evaluation of the toxicity induced by mussels (Mytilus galloprovincialis) from two sites of the Moroccan Atlantic coast in mice

Atlantic coast in mice. Preliminary studies showed that seawater contains heavy metals from domestic, agricultural and industrial wastes. Marine bivalves concentrate these pollutants by filtration and serve as vectors in human exposure. The objective of this study was to determine the concentration of heavy metals; cadmium (Cd); chromium (Cr), and lead (Pb) in mussels (Mytilus galloprovincialis) collected in two coastal sites; Jorf Lasfar (JL) (neighbouring a phosphate processing platform) and Oualidia (OL) (a vegetable growing area) located at 120 and 190 km south of Casablanca, respectively. Another objective was to test and compare the toxicity of these mussels on mice. The results indicated the presence of heavy metals (Cd, Cr, and Pb) in mussels at different concentrations, depending on the collection period. Higher concentrations were obtained at JL than at OL: for example, Cd concentrations were 80 +/- 15 to 199 +/- 28 versus 23 +/- 5 microg/g mussel dry weight, respectively. Cramming with mussel powder did not increase Cd, Cr, or Pb concentration in either liver or kidneys of treated mice. The relative kidney weights were reduced. Increased glucose urea was observed in animals' urine. Treatment with mussels from OL induced significant reduction (20%) in mice body weight, together with an increase in creatinuria. These results indicate that mussels collected from OL are more harmful than those obtained from JL are. All these mussels should not be recommended for human consumption.     

Resting spore formation ofLeptocylindrus danicus (Bacillariophyceae) during short time-scale upwelling and its significance as predicted by a simple model

Resting spore formation during short time-scale upwelling and its significance were investigated in the field and by a simple theoretical model. Field observations of spore formation ofLeptocylindrus danicus were made off Izu Peninsula, Japan. A rapid increase in ratio of resting spore to vegetative cell numbers indicated thatL. danicus formed resting spores quickly as a response to nutrient depletion in the upwelled water, although only a very low number of resting spores was found in the upwelling. A simple model was constructed to investigate the possible advantages of spore formation during short time-scale upwelling. This showed that there is a critical time-scale for resting spore formation to be advantageous. The nutrient depletion period of the upwelling off Izu was shorter than the critical time-scale determined by the model. Rapid-sinking of resting spores may increase further the critical time-scale, unless spores return with upwelling water. For short time-scale upwelling, the vegetative cell may be better suited than the resting spore for enduring a short period of nutrient depletion. Contribution from Shimoda Marine Research Center, University of Tsukuba, No. 475.     

Zonal distribution of pelagic decapoda (crustacea) in the eastern North Atlantic and its relation to the physical oceanography

The day and night vertical distribution of pelagic decapods at six stations in the eastern North Atlantic on 20°W have been analysed using principal components analysis coupled with varimax rotation. The species have been classified into fourteen faunal groups and the principal components scores have been used to typify the Zoogeographic distribution and vertical migratory behaviour of these groups. The same method was used to classify the samples and it was found that the resulting zonation could be partly explained by the classical picture of oceanic circulation in the eastern North Atlantic. The explanatory power of this Zoogeographic hypothesis was quantified using Procrustes analysis and was found to explain about 50% of the sums-of-squares of the between samples correlation matrix.     

Diagnosis on the state of healthiness,quality of the coast and biological resources 'case of the Moroccan Atlantic coast' (City of El Jadida)

In this study, we present a diagnosis concerning the state of healthiness of the coast of the city of El Jadida by: characterisation of the various collectors rejected in sea without any preliminary treatment, measure of the physicochemical parameters of seawater from sampling stations, evaluation of the concentration of certain heavy metals (Cd, Cu, Zn, Fe and Mn) in four species of algae, which shows that metal contents vary according to the species and the sampling stations, measure of the metal content in mussels, which varies according to the site. A comparative study with the data of the literature shows that algae and mussels generally present values that are weaker than those coming from other geographical areas.     

Distribution of live benthic foraminifera in the Ría de Vigo (NW Spain)

The spatial and vertical distributions of live benthic foraminifera from the muddy central axis of the Ría de Vigo were examined under downwelling and upwelling conditions. The spatial distribution of the main benthic foraminiferal species is controlled by salinity variations (San Simón Assemblage), food availability (Outer Ría Assemblage) and oxygen concentrations and/or reducing microenvironmental conditions in the sediment (Inner Ría Assemblage).The microhabitat distribution of benthic foraminifera is mainly dependant on the oxygenation/redox conditions in the sediment and the vertical segregation of food. In the inner areas of the ría, low oxygen and/or reducing microenvironmental conditions prevent the vertical segregation of microhabitats. In outer areas oxygen penetration is deep but microhabitat partitioning only occurs in the presence of additional food resources (mainly fresh organic carbon from phytoplankton blooms) which triggers the colonisation of the surface layer by new species and the migration upwards and reproduction of opportunistic species.     

Differences in the abundance and distribution of copepods in two estuaries of the Basque coast (Bay of Biscay) in relation to pollution

The abundance and spatial distribution of copepod species werecompared in the euhaline region of the polluted estuary of Bilbao[mean biological oxygen demand (BOD): 49748.05 kg day^–1in 1996] and the unperturbed estuary of Urdaibai. Sampling wasperformed at fixed salinity sites, where data of temperature,dissolved oxygen saturation, particulate organic matter, Secchidisk depth and chlorophyll were also obtained. Differences betweenthe estuaries and within the estuaries for environmental variablesand copepod abundances were tested statistically. The dominantspecies Acartia clausi and Paracalanus parvus differed significantlyin abundance between estuaries, and most of neritic speciesdiminished more drastically with decreasing salinity in Bilbaoby the effect of pollution. The different responses observedamong species in relation to pollution and water desalinationare discussed. The lack of the brackish-water species in Bilbaoindicated that water quality worsening upward the estuary ofBilbao not only limited the penetration of neritic species butalso prevented the development of autochthonous estuarine species.At the outer euhaline region of Bilbao, however, pollution wasfound to be low enough to enhance the development of tolerantneritic species that are favoured under moderate pollution conditions.Results indicate that comparisons of copepod abundances anddistributions with salinity in estuaries may be a useful toolto evaluate the health of the different estuarine pelagic habitats.     

Epiphytism in a subtidal natural bed of Gracilaria gracilis of southwestern Atlantic coast (Chubut, Argentina)

The diversity of epiphytes, their temporal abundance variation and the anatomical structure of host–epiphyte interfaces were studied in the agarophyte Gracilaria gracilis from a natural bed in Bahía Bustamante, Chubut Province, Argentina. Twenty-nine algal species were recorded as epiphytes during 2 years of monthly sampling (March 2006–February 2008). Total epiphyte density ranged between 0.037 ind. cm^?2 (November 2006) and 39.37 ind. cm^?2 (April 2007), with higher density values throughout the second sampling year. Ceramiales species were the most abundant epiphytes. The density of Ceramium rubrum ranged from 0.09 ind. cm^?2 (52 % of the total amount) in September 2006 to 17.4 ind. cm^?2 (44.18 % of the total amount) in April 2007. Epiphyte infection was more dependent on spore recruitment and sporeling development, especially on thalli derived from fragmentation, than on seasonal environmental variations. The different infections were analysed, taking into account the epiphytic attachment strength and invasiveness and the degree of damage inflicted on the host. Calothrix confervicola was one of the most abundant species. This epiphyte, weakly attached to the host surface, generated no host tissue damage. In contrast, C. rubrum, Polysiphonia abscissa and other Ceramiales were the species that caused more damage to the host because their rhizoids penetrated the cortical portion of the host thallus, sometimes reaching the medullary tissue. Some generalisations and characterisations of the different epiphyte groups in relation to their consequences to Gracilaria spp. are presented.     

Fine structure of bovine lens epithelial cells in vitro in relation to modifications induced by a retinal extract (EDGF)

Cultured bovine lens epithelial cells are polygonal in shape. In confluent and multilayer cultures they exhibit elaborate arrays of 6 nm filaments, bundles of intermediate-sized filaments, and a fibrous meshwork of subcellular and intercellular material. Cells grown in the presence of a retinal extract (RE) have a higher growth rate, and are smaller and more regular in shape. In them the 6 nm filaments are mostly aligned in sheets, the intermediate-sized filaments form a fine network, and the cells are closely apposed to the plastic substratum. Some homogeneous material is formed intercellularly in older cultures. Cellular elongation, induced in the former cultures by the addition of RE, is accompanied by an alignment of cytoskeletal elements, including microtubules, parallel to the long axis. Other structural features are similar in all cell types. The response to RE is discussed in terms of shape modulations associated with the restricted expression of structural characteristics acquired in vitro.     

Patterns in the distribution, abundance and body size of carabid beetles (Coleoptera: Caraboidea) in relation to dispersal ability

The effects of dispersal ability, measured as two wing size categories (brachypterous vs. macropterous), on the distribution, abundance and body size, and on the relationships between these variables were examined in eighty-four species of carabid beetles over twenty-two sites in the northern Iberian peninsula. Geographic ranges of species (restricted to the northern Iberian peninsula vs. widespread—European or wider range) were also taken into account in the analyses because macropterous species significantly tended to exhibit wider geographic ranges than did brachypterous species. Regional distributions were wider in brachypterous-restricted and brachypterous-widespread species than in macropterous-widespread species. The three groups did not differ in abundance. Differences in regional distributions between groups may be explained by referring to a trade-off between dispersal ability and establishment ability indicated in the literature. Macropterous species would occupy relatively few sites due to a high frequency of unsuccessful colonizations. The relationships between regional distribution and abundance were positive for all the three groups, brachypterous-restricted, brachypterous-widespread and macropterous-widespread species. The regression line for the last group showed a lower elevation than those for brachypterous-restricted and brachypterous-widespread species. This fact was probably due to differences in regional distributions between groups. No relationship between abundance and body size was significant. Regressions of regional distribution on body size were positive in brachypterous-restricted and brachypterous-widespread carabids, but the relationship was not significant in macropterous-widespread carabids. These results were interpreted in terms of differences in body size–dependency of travelling velocities between flying and running carabids.     

Seasonal dynamics of Acartia bifilosa and Eurytemora affinis (Copepods: Calanoida) in relation to abiotic factors in the northern Baltic Sea

Distributions in the time and space

Seasonal dynamics of Acartia bifilosa and Eurytemora affinis (Copepods: Calanoida) in relation to abiotic factors in the northern Baltic Sea     

Foraging time allocation in relation to sex by the gulf coast fiddler crab (Uca panacea)

Summary Schoener (1971) proposed that the reproductive demands of animals should be important in shaping their foraging behavior because fitness is affected. He defined two forager types: energy maximizers (reproductive success depends on energetic intake) and time minimizers (reproductive success depends on time spent in activities other than foraging), and suggested that females most often illustrate the former and males the latter. We tested whether mating activities influence the foraging behavior of Uca panacea, and the predictions that females would be energy maximizers because of their reproductive strategy and that males would also be energy maximizers because of their courtship activity. Time allocated to foraging by 800 male and female fiddler crabs (at two sites) was quantified; no significant difference in foraging time was found between the sexes. Both male and female crabs allotted a large portion of their time to foraging because both sexes depend on stored energy during their reproductive bouts. Our results show that the particular forager type can be predicted based on reproductive demands, but a forager type can not always be assigned to a particular sex without consideration of all important ecological and physiological factors determining reproductive success.     

The modalities of the sexual cycle of Octopus vulgaris in the southern Moroccan Atlantic (Tantan, Boujdour)

The reproduction of Octopus vulgaris between Tan Tan and Boujdour is studied. The samples used are sorted monthly from commercial catches of coastal trawlers operating in this area from December 2001 to May 2003. The study shows that sexual maturity is in advance for males than for females. Two spawning periods are made out by the follow-up of the RGS: a spring period from March to July, and an autumnal period, which is less intense, between September and October. The division of spermatogonia and spermatocytes reaches its maximal intensity in July and December, whereas the spermiogenesis is active until the time of mating. The vitellogenesis starts in mid-December and extends until the following spawning period. This reveals a later gonadic development for females than for males; approximately seven months for females and three months for males.     

Vertical distribution of Atlantic salmon (Salmo salar) as a function of illumination

The vertical distribution of cultured Atlantic salmon larger than 1 kg was monitored by hydroacoustics in both a shallow (6 m) and a deep (20 m) cage. Surface light levels and fish distribution were registered for three periods throughout the year. The two fish groups were fed calculated rations twice a day. During the winter and spring (including vernal equinox), the fish were distributed at around 5 m depth in both cages when not feeding. Around summer solstice, the fish preferred deeper waters when not feeding. The light dependency of the vertical migration was pronounced, and indicates clearly that even a 20 m deep cage is not deep enough to meet the depth requirements of large Atlantic salmon during summer.