Identification of benthic egg masses and spawning grounds in commercial squid in the English Channel and Celtic Sea: Loligo vulgaris vs L. forbesii

2021 ◽  
Vol 241 ◽  
pp. 106004
Author(s):  
Vladimir Laptikhovsky ◽  
Gavan Cooke ◽  
Christopher Barrett ◽  
Sophie Lozach ◽  
Eleanor MacLeod ◽  
...  
Keyword(s):  
English Channel ◽  
Spawning Grounds ◽  
Egg Masses ◽  
Loligo Vulgaris ◽  
Celtic Sea

scholarly journals Bottom temperature and in situ development of chokka squid eggs (Loligo vulgaris reynaudii) on mid-shelf spawning grounds, South Africa

2009 ◽  
Vol 66 (9) ◽  
pp. 1967-1971 ◽  
Author(s):  
Anè Oosthuizen ◽  
Mike J. Roberts
Keyword(s):  
South Africa ◽  
Bottom Temperature ◽  
Egg Development ◽  
Spawning Grounds ◽  
Loligo Vulgaris ◽  
Laboratory Results ◽  
Temperature Environment ◽  
Development Data ◽  
Shelf Temperature

Abstract Oosthuizen, A., and Roberts, M. J. 2009. Bottom temperature and in situ development of chokka squid eggs (Loligo vulgaris reynaudii) on mid-shelf spawning grounds, South Africa. – ICES Journal of Marine Science, 66: 1967–1971. The aim of the study was to test the development success of squid eggs on the mid-shelf (60–150 m deep) spawning grounds in relation to previous laboratory results, and to describe the mid-shelf temperature environment and how it could affect egg development. A series of in situ egg incubation experiments was conducted on the mid-shelf (∼119 m deep) spawning grounds using cages, temperature sensors, and acoustic releases for retrieval. Newly spawned eggs were collected by scuba, and continuous temperature data were collected at two points between the known inshore spawning grounds and the mid-shelf areas. Temperature variations followed a seasonal warming and cooling cycle, with superimposed peaks and troughs. Egg development data indicated that warm temperature peaks (10–13°C) are sufficient for normal development of eggs on the mid-shelf. Egg development time on the mid-shelf was 2–3 times longer (50–60 vs. 20–30 d) than inshore. The scarcity of abnormalities (0.45%) disputes previous laboratory results that suggested that ∼50% of eggs would suffer abnormalities in the colder mid-shelf temperature environment.

scholarly journals Cascading Over the Continental Slope of Water from the Celtic Sea

1949 ◽  
Vol 28 (3) ◽  
pp. 719-750 ◽  
Author(s):  
L. H. N. Cooper ◽  
David Vaux
Keyword(s):  
Continental Shelf ◽  
Continental Slope ◽  
English Channel ◽  
The South ◽  
Celtic Sea

In the Celtic Sea, to the south of Ireland, water in some winters becomes sufficiently cooled and heavy to flow to the edge of the continental shelf and to run down the continental slope to a depth of several hundred metres. A theory of the phenomenon, termed ‘cascading’, has been developed. Three winters have been examined in detail.In February 1927 much water, heavy enough to cascade, was present in the Celtic Sea and also in the English Channel. A probable course and speed of the cascading water over the shelf has been established. Since there were few observations of salinity and temperature over or beyond the slope, and none of oxygen anywhere, the theory cannot be completely established on the basis of the 1927 observations, full though they were.

scholarly journals On changes of sea temperature in the English Channel

1960 ◽  
Vol 39 (3) ◽  
pp. 449-458 ◽  
Author(s):  
A. J. Southward
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Air Temperature ◽  
Sea Surface ◽  
English Channel ◽  
Sea Temperature ◽  
Celtic Sea

In a series of papers dealing with changes in the distribution of intertidal animals around Britain, and especially along the English Channel, attention was drawn to some local aspects of the general warming-up of sea and air that has taken place in the last 50 years (Southward & Crisp, 1954, 1956; Crisp and Southward, 1958). In the first of these papers smoothed values of annual mean air temperature at Plymouth Hoe, and sea surface temperature of the southern Celtic Sea were given, the latter values being based on Smed (1952). The graphs showed a rise of about 1° C in the air temperature and 0·5° C in sea temperature during 50 years.

scholarly journals The physical and chemical oceanography of the waters bathing the continental slope of the Celtic Sea

1952 ◽  
Vol 30 (3) ◽  
pp. 465-510 ◽  
Author(s):  
L. H. N. Cooper
Keyword(s):  
Atlantic Ocean ◽  
Continental Slope ◽  
Life Histories ◽  
English Channel ◽  
South West ◽  
Chemical Oceanography ◽  
Celtic Sea ◽  
The Right ◽  
Physical And Chemical ◽  
Made In

Knowledge of the hydrography of the English Channel and Celtic Sea is needed as a background for the life histories of the mackerel, pilchard and herring and, indeed, of every organism living within range of the Plymouth Laboratory. Such knowledge can never be fully attained until we know more of the exchanges with the deep Atlantic Ocean which take place 200–300 miles to the south-west and west over the continental slope. Moreover, at the slope we shall need to know not only what waters move in and out but what move up and down. Long ago Storrow (1925), and no doubt others, saw clearly some of the problems here to be discussed, but they were unable to bring factual evidence to bear. A critical reconstruction of the considerable but fragmentary observations in the neighbourhood of the continental slope of the Celtic Sea will be presented here and supplemented by observations made in 1950 with the generous co-operation of the vessels of the National Institute of Oceanography (Discovery Committee) and in 1948 by H.M. Surveying Ship Dalrymple. Though many of the conclusions remain tentative, it should now be easier to design observational work at sea to test specific hypotheses at the right time and place by the methods of experimental oceanography. The numerical results in 1950 will be published by the Conseil International pour l'Exploration de la Mer.

scholarly journals Citizen science in the marine environment: A case-study estimating common dolphin densities in the north-east Atlantic

2019 ◽  
Author(s):  
James R Robbins ◽  
Lucy Babey ◽  
Clare B Embling
Keyword(s):  
Citizen Science ◽  
Common Dolphin ◽  
Bay Of Biscay ◽  
English Channel ◽  
East Atlantic ◽  
Science Data ◽  
North East ◽  
The North ◽  
Celtic Sea ◽  
Common Dolphins

Background. Citizen science is increasingly popular and has the potential to collect extensive datasets at lower costs than traditional surveys. Ferries have been used to collect data on cetacean populations for decades, providing long-term time series allowing for monitoring of cetacean populations. One cetacean species of concern is the common dolphin, which have been found stranded around the north-east Atlantic in recent years, with high numbers on French coasts being attributed to fisheries bycatch. We estimate common dolphin densities in north-east Atlantic and investigate the power of citizen science data to identify changes in marine mammal densities and areas of importance. Materials & Methods. Data were collected by citizen scientists on ferries between April and October in 2006 - 2017. Common dolphin sightings data from two ferry routes in the Bay of Biscay (n= 569), Celtic Sea (n= 260), and English Channel (n= 75) were used to estimate detection probabilities with detection functions. Density Surface Models estimated density across ferry routes, accounting for the influence of environmental (chlorophyll a, sea surface temperature, depth, and slope), spatial (latitude and longitude) and temporal terms (year and Julian day). Results. Overall detection probability was highest in the English Channel (0.384) and Bay of Biscay (0.348), and lowest in the Celtic Sea (0.158). Common dolphins were estimated to occur in higher densities in the Celtic Sea (0.400 per km) and the Bay of Biscay (0.319 per km), with low densities in the English Channel (0.025 per km). Densities in the Celtic Sea have been relatively stable on the ferry route since 2006 with a slight decrease in 2017. Densities peaked in the Bay of Biscay in 2013 with lower numbers since. The general trend in the English Channel is for increasing densities of common dolphins over time since 2009. Discussion. This study highlights the effectiveness of citizen science data to investigate the distribution and density of cetaceans. The densities and temporal changes shown by this study are representative of those from wider-ranging robust estimates. We highlight the ability of citizen science to collect data over extensive periods of time which complements traditional surveys. Such long-term data are important to identify changes within a population; however, citizen science data may, in some situations, present challenges. We provide recommendations to ensure high-quality data which can be used to inform management and conservation of cetacean populations.

Variation in the whistle characteristics of short-beaked common dolphins, Delphinus delphis, at two locations around the British Isles

2007 ◽  
Vol 87 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Ina C. Ansmann ◽  
John C. Goold ◽  
Peter G.H. Evans ◽  
Mark Simmonds ◽  
Simon G. Keith
Keyword(s):  
Ambient Noise ◽  
Low Frequency ◽  
English Channel ◽  
Delphinus Delphis ◽  
Context Group ◽  
Population Structuring ◽  
The Common ◽  
Celtic Sea ◽  
Almost All ◽  
Common Dolphins

The vocal repertoire of many delphinid odontocetes includes narrowband tonal whistles used mainly for communication. The aim of this study was to describe the whistle repertoire of short-beaked common dolphins, Delphinus delphis, recorded in the Celtic Sea between May and August 2005. The 1835 whistles recorded were classified into six broad categories and 30 sub-types, of which simple upsweeps and downsweeps were the most common. Furthermore, the parameters duration, inflections, steps and various frequency variables were measured. The whistles covered a frequency span from 3.56 kHz to 23.51 kHz and had durations between 0.05 and 2.02 seconds. Whistle parameters varied with behavioural context, group size and between encounters. The whistle repertoire of Celtic Sea common dolphins was compared to that of D. delphis from the Western Approaches of the English Channel, recorded during a survey between January and March 2004. The relative abundances of the broad whistle types did not differ between the two locations, but most whistle parameters were significantly different: almost all frequency variables measured were significantly higher in English Channel whistles. This may indicate some degree of population structuring of short-beaked common dolphins around Britain. Alternatively, the common dolphins in the English Channel may have shifted the frequencies of their vocalizations up to avoid masking by low-frequency ambient noise produced by high levels of vessel traffic in this area.

scholarly journals Chemical properties of the sea water in the neighbourhood of the Labadie Bank

1951 ◽  
Vol 30 (1) ◽  
pp. 21-26 ◽  
Author(s):  
L. H. N. Cooper
Keyword(s):  
Sea Water ◽  
Chemical Properties ◽  
English Channel ◽  
Chemical Analyses ◽  
Celtic Sea

A number of excursions to the Celtic Sea have been made, first, to obtain for Dr D. P. Wilson water as contrasted as possible with that in the English Channel near Plymouth, and secondly to obtain answers to hydrographical queries. This paper presents some of the chemical findings which may prove to be relevant to Wilson's investigations on the development of the young planktonic stages of invertebrates. Since not all sea water in the Celtic Sea was likely to be equally suitable for his work, some means was needed for quickly assessing waters on the spot. There are a number of objections to the use of phosphate or other chemical analyses on board so that examination of plankton hauls was chosen. Suitable water was selected on the basis of the bulk and variety of zooplankton and the presence of species known to indicate ‘elegans’ water. The 2 m. stramin ring-trawl, fished for the standard half-hour oblique haul, was used.

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