scholarly journals Small-scale spatio-temporal variability in ichthyoplankton and zooplankton distribution in relation to a tidal-mixing front in the Irish Sea

2005 ◽  
Vol 62 (6) ◽  
pp. 1021-1036 ◽  
Author(s):  
O. Lee ◽  
R.D.M. Nash ◽  
B.S. Danilowicz
Keyword(s):  
Temporal Dynamics ◽  
Fish Larvae ◽  
Sampling Period ◽  
Tidal Mixing ◽  
Irish Sea ◽  
Small Scale ◽  
Surface Salinity ◽  
Average Value ◽  
Tidal Mixing Front ◽  
Spatio Temporal

Abstract This study examines the spatio-temporal dynamics of fish larvae and their prey at a tidal-mixing front in the central Irish Sea. The distribution of ichthyoplankton and zooplankton was analysed in relation to environmental variables (depth, surface temperature, surface salinity, and water column stratification) using Redundancy Analysis (RDA). Significant interannual variability in the formation and position of the tidal-mixing front coincided with large differences in the species abundances of both ichthyoplankton and zooplankton. During the summer, ichthyoplankton and zooplankton communities were structured by a combination of depth and hydrography, and the variability in species composition was directly related to the average value of the stratification parameter. Several ichthyoplankton species were consistently associated with frontal waters, while fewer species were concentrated in mixed water masses throughout the sampling period. The distribution of individual zooplankton species was also examined, and water mass affinities were shown to vary with developmental stage.

Fickian Transport and the Dispersal of Fish Larvae in Estuaries

1982 ◽  
Vol 39 (8) ◽  
pp. 1150-1163 ◽  
Author(s):  
L. Fortier ◽  
W. C. Leggett
Keyword(s):  
Vertical Distribution ◽  
Fish Larvae ◽  
Sampling Period ◽  
Clupea Harengus ◽  
Tidal Mixing ◽  
Larval Abundance ◽  
Lawrence Estuary ◽  
Larval Stages ◽  
Diel Vertical Migrations ◽  
Average Size

We studied the regulation of ichthyoplankton dispersion in the two-layer circulation of the St. Lawrence upper estuary by determining larval abundance and vertical distribution during high frequency sampling at three stations in May, June, and July, 1979. Monthly variations in capelin (Mallotus villosus) and Atlantic herring (Clupea harengus harengus) abundance were in agreement with the seasonal trends previously reported. Capelin larvae were concentrated in the surface layer, a situation which resulted in seaward drift. No significant growth was observed over the 60-d sampling period indicating continuous recruitment to, and removal from, the sampling area. Herring larvae were concentrated in the deep layer and were carried landward. The average size of herring larvae increased from the downstream to the upstream stations. Short-term fluctuations in the abundance and vertical distribution of the two species were interpreted in terms of the Fickian representation of transport for partially mixed estuaries. The major source of variation in abundance, at a given station, was the tidal advection of horizontal gradients. Capelin larvae and herring larvae smaller than 10 mm did not actively cross the pycnocline and were not submitted to the diffusive effect of the vertical current shear. The dispersal of these larvae was apparently passive. Herring larvae larger than 10 mm performed diel vertical migrations across the pycnocline and were dispersed in the horizontal plane at a faster rate than a passive contaminant of the environment. We conclude that the Fickian approach can be profitably applied to studies of dispersal and mortality of early larval stages of fish in estuaries.Key words: ichthyoplankton, St. Lawrence estuary, dispersion, transport, vertical distribution, diel migrations, variability, abundance, tidal mixing, Fickian

Biological studies in the vicinity of a shallow-sea tidal mixing front. I. Physical and chemical background

1985 ◽  
Vol 310 (1146) ◽  
pp. 407-433 ◽  
Keyword(s):  
Ammonium Nitrogen ◽  
Tidal Mixing ◽  
Irish Sea ◽  
Total Biomass ◽  
Shallow Sea ◽  
High Biological Activity ◽  
Biological Studies ◽  
Chemical Background ◽  
Tidal Mixing Front ◽  
Physical And Chemical

A study has been made of the distribution and activities of bacteria and zooplankton as they varied seasonally in 1980 and 1981 in the vicinity of a shallow-sea tidal mixing front in the western Irish Sea (approximate position 53° 20' N, 5° 45' W to 53° 50' N, 5° 0' W ). This paper presents the physical and chemical background to these studies as shown by the variations in temperature and salinity and concentrations of chlorophyll a , phaeopigments, cellular adenosine triphosphate (ATP), nitrate, nitrite and ammonium nitrogen, in sections normal to the front. Observations at drogue stations were made to establish the extent of diurnal variations in these properties but these appeared to be small relative to other variations. As the front developed, higher chlorophyll a concentrations appeared in the surface stratified water, in contrast to the bottom stratified water and mixed water, with highest concentrations at the surface at the stratified side of the front and in subsurface patches in the vicinity of the pycnocline. As the phytoplankton populations increased nitrate became depleted in the surface stratified water but nitrite and ammonium nitrogen concentrations remained at about the same levels. Cellular ATP concentration did not appear to be a useful measure of total biomass but indicated high biological activity in the surface stratified water.

Biological studies in the vicinity of a shallow-sea tidal mixing front VII. The frontal ecosystems

1985 ◽  
Vol 310 (1146) ◽  
pp. 555-571 ◽  
Keyword(s):  
Nitrogen Cycling ◽  
Dynamic Equilibrium ◽  
Standing Stock ◽  
Tidal Mixing ◽  
Irish Sea ◽  
Heterotrophic Activity ◽  
Plume Front ◽  
Biological Studies ◽  
Tidal Mixing Front ◽  
Standing Stocks

Three, possibly four, ecosystems forming seasonally are associated with the tidal mixing front in the western Irish Sea. They are distinguished not only by the presence or absence of particular species but by their relative intensities of heterotrophic activity and degree of organization as shown in the number of statistically significant correlations between the variables pertaining to them. The mam body of surface stratified water, at first dominated by an expanding population of phototrophs, attains during the summer a state of dynamic equilibrium in which the standing stock of phytoplankton remains at about the same level, its primary productivity being balanced by high levels of heterotrophic activity and cycling of nitrogen. The bottom stratified water, besides having minimal photosynthetic activity, shows low zooplankton stocks, low heterotrophic activity and the lowest level of organization. Mixed water has lower standing stocks, less heterotrophic activity, lower rates of nitrogen cycling, and is a less highly organized system than the surface stratified water. The stratified water in a band about 10 km wide adjacent to the front does not show conspicuously higher total standing stocks of phytoplank ton, bacteria and zooplankton in the water column down to the pycnocline, than the rest of the stratified water. Animals migrating into it do not provide an appreciable extra source of nutrients for the phytoplankton. It does, however, show much higher heterotrophic activity and rates of nitrogen cycling than the rest of the stratified water. This is tentatively attributed to increased photosynthesis, consequent on the redistribution of phytoplankton by frontal eddies, being taken up in increased heterotrophic activity rather than in growth of the phytoplankton itself. A similar situation appears to exist at the plume front in Liverpool Bay but here there is the additional factor of collection at the front of particulate organic matter derived from river inflow.

scholarly journals The bluefish Pomatomus saltatrix (Pisces: Pomatomidae) in the Adriatic and Tyrrhenian Seas, can we call it climate invader?

2020 ◽  
Author(s):  
Jacopo Cerri ◽  
Ernesto Azzurro
Keyword(s):  
Invasive Species ◽  
Climate Warming ◽  
Temporal Dynamics ◽  
Small Scale ◽  
Ecological Knowledge ◽  
Pomatomus Saltatrix ◽  
Warm Water Species ◽  
Northward Expansion ◽  
Spatio Temporal ◽  
Water Species

Here, we investigate the recent spatio-temporal dynamics of the bluefish Pomatomus saltatrix, a warm water species, which is considered to have conquered the northern Mediterranean coasts due to climate warming. Capitalizing two independent surveys carried out through online questionnaires and vis-à-vis interviews, we accessed the ecological knowledge of 640 recreational fishers, and 206 small-scale fishers, respectively. Respondents provided coherent evidence of a rapid northward expansion of the bluefish along the Tyrrhenian and Adriatic Seas at an estimated speed of 0.8-1.4 degrees of latitude per year. Most fishers in the two seas believed the bluefish to negatively affect both fishing activities and the environment, just as if it was an invasive species and this negative perception was positively correlated with increasing bluefish abundances. The phenomenological effects of this widespread outbreak can be assimilated to a large invasion across various sectors of the Mediterranean Sea, posing the urgency of manage this issue and better understanding its linkage to climate drivers.

scholarly journals The shifting distribution of Mediterranean fishes: a spatio-temporal assessment based on Local Ecological Knowledge .

2019 ◽  
Author(s):  
Ernesto Azzurro ◽  
Valerio Sbragaglia ◽  
Jacopo Cerri ◽  
Michel Bariche ◽  
Luca Bolognini ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Temporal Dynamics ◽  
Local Ecological Knowledge ◽  
Rapid Change ◽  
Species Abundance ◽  
Global Ocean ◽  
Small Scale ◽  
Ecological Knowledge ◽  
The Mediterranean ◽  
Spatio Temporal

A major problem worldwide is the rapid change in species abundance and distribution, which is rapidly restructuring the biological communities of many ecosystems under changing climates. Tracking these transformations in the marine environment is crucial but our understanding is often hampered by the absence of historical data and by the practical challenge of survey large geographical areas. Here we focus on the Mediterranean Sea, a region which is warming faster than the rest of the global ocean, tracing back the spatio-temporal dynamic of species, which are emerging the most in terms of increasing abundances and expanding distributions. To this aim, we accessed the Local Ecological Knowledge (LEK) of small-scale and recreational fishers reconstructing the dynamics of fish perceived as ‘new’ or increasing in different fishing area. Over 500 fishers across 95 locations and 9 different countries were interviewed and semi-quantitative information on yearly changes in species abundance was collected. Overall, 75 species were mentioned by the respondents, being the most frequent citations related to warm-adapted species of both, native and exotic origin. Respondents belonging to the same biogeographic sectors described coherent spatio-temporal dynamics, and gradients along latitudinal and longitudinal axes were revealed. This information provides a more complete understanding of recent bio-geographical changes in the Mediterranean Sea and it also demonstrates that adequately structured LEK methodology might be applied successfully beyond the local scale, across national borders and jurisdictions. Acknowledging this potential through macro-regional coordination, could pave the ground for future large-scale aggregations of individual observations, increasing our potential for integrated monitoring and conservation planning at the regional or even global level.

scholarly journals Structure and spatio-temporal dynamics of the artisanal small-scale fisheries at the future MPA of “Taza” (Algerian coast, SW Mediterranean)

2018 ◽  
Vol 19 (3) ◽  
pp. 555 ◽  
Author(s):  
IBRAHIM BOUBEKRI ◽  
ALEX JAMES CAVEEN ◽  
ABDALLAH BORHANE DJEBAR ◽  
RACHID AMARA ◽  
HUBERT MAZUREK
Keyword(s):  
Temporal Dynamics ◽  
Field Work ◽  
Management Plan ◽  
Small Scale ◽  
Target Species ◽  
Small Scale Fisheries ◽  
The Future ◽  
Mullus Surmuletus ◽  
Spatio Temporal ◽  
Management Approaches

Artisanal Small-Scale Fisheries (SSFs) are a primordial and very diverse activity in the Mediterranean, also within Marine Protected Areas (MPAs). This diversity is explained in terms of target species, gears, and fishing strategies. The main objective of this work was to investigate the spatio-temporal dynamics of artisanal SSFs of the future MPA of “Taza” (Algeria, SW Mediterranean). Data were collected through direct assessment of daily landings and using questionnaires. They were the subject of multivariate analyses that allowed us to identify the métiers practiced by artisanal fishers. During the one year (May 2013 to April 2014) field work period, 1330 fishing trips and 1613 fishing operations in 16 fishing grounds were recorded in the Ziama fishing harbor, where 15.2 tons of total catch was assessed. Our results show that, in the study area, the boats are predominantly gillnetters and that among the five métiers characterized by target species, gear type, fishing grounds, and fishing seasons, two métiers (“Mullus surmuletus trammel net” and “Sparids monofilament gillnet”) are practiced throughout the year, while the remaining three (“Sarda sarda driftnet”, “Merluccius merluccius set gillnet”, and “Pagellus set gillnet”) are specific to a determined period of the year. The ‘Mullus surmuletus trammel net’ métier represents 40% of the total fishing operations, of which 57.5% are carried out in the coastal sector at - 25 m. This study could contribute to defining the appropriate management approaches for SSFs in the future MPA of “Taza” by providing baseline information to build a sound management plan. In Algeria, it will certainly serve as a scientific reference in terms of zoning, protection of biodiversity, and specific monitoring at particular locations and periods of the year for the sustainable management of MPAs.

Biological studies in the vicinity of a shallow-sea tidal mixing front II. The distribution of bacteria

1985 ◽  
Vol 310 (1146) ◽  
pp. 435-444 ◽  
Keyword(s):  
Thermal Stratification ◽  
Staining Method ◽  
Late Summer ◽  
Early Spring ◽  
Tidal Mixing ◽  
Irish Sea ◽  
Biological Studies ◽  
Sampling Regime ◽  
Tidal Mixing Front ◽  
Nested Analysis

The work described in this paper was carried out in the summers of 1980 and 1981 in the western Irish sea. The purpose was to ascertain the effects of the annual thermal stratification which occurs in the region on the distribution of bacteria. The sampling regime involved a line of ten stations on a transect normal to a tidal mixing front, sampled at four depths in 1980 and six depths in 1981. Estimation of bacterial numbers was carried out by using a modified acridine orange epifluorescent staining method. The data was statistically analysed by using a nested analysis of variance technique which showed a stable and relatively uniform winter—early spring distribution with low overall counts which became more patchy as the spring progressed and the counts increased. In late summer the distribution became more uniform again within the mixed and stratified water masses but with significantly higher counts in the stratified water.

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