[From BA handbook, 1896]

SKETCH OF THE MARINE BIOLOGY OF THE ISLE OF MAN.

By W. A. HERDMAN, D.Sc., F.R.S

(With a Chart).

 
Sketch Map and Section of the Irish Sea-Basin

The Isle of Man is interesting ground to the Marine Biologist, as it presents, within a very limited area, sea coasts and sea-bottom of very varied characters, and a wide range of depth. There are cliffs and reefs of sandstone, limestone, and hard metamorphic rocks there are sandy hays, gravel beaches, and mud flats and, within a distance of 12 miles from the shore, there are depths up to nearly 80 fathoms. This permits of a great variety in the marine fauna and flora, especially around the southern end of the island, where, within a radius of about a mile from the Port Erin Biological Station, many different kinds of shore and of sea-bottom are met with.

On account of the set of the tides, Port Erin Bay and the sea around the Calf receive directly the water which has come up the centre of St. George’s Channel, unpolluted by contact with land, and undiluted by the entrance of any large streams. Consequently the sea off the south end of the Isle of Man is of very constant high specific gravity (over 1027), and of great purity; many of the food fishes of the Irish Sea come there to spawn, and the pelagic fauna caught in the surface tow-nets is abundant, and at certain times contains oceanic or southern organisms (such as Siphonophora), which have been carried in from the Atlantic.

Probably on account of the purity and salinity of the water, and on account of the abundance of pelagic life, the south end of the Isle of Man would be the most suitable spot in the Irish Sea for a Sea-fish Hatchery. Many of our most important food fishes, upon which the fisheries of the Irish Sea depend, spawn in the deep water around the southern end of the Isle of Man; and experiments with drift-bottles have shown that, on the whole, small floating objects, such as fish-eggs and embryos, placed in the water to the west of the Isle of Man tend to be carried to the Irish coast opposite, while those put on the eastern side go to the Lancashire and Cheshire coast. Probably, then, the Manx waters are the spawning grounds for the fish of both the English and Irish coasts. Some experiments carried on at the Port Erin Biological Station have shown that it is easy to hatch out in the water of the bay, without any special precautions and with very simple apparatus, the eggs of food fishes both round and flat.

The Biological Station and Aquarium at Port Erin were established by the Liverpool Marine Biological Committee, and were formally opened on June 4th, 1892, by his Excellency the Lieut.-Governor, Mr. Spencer Walpole. Marine Biology deals with the development, structure, actions, and relationships of -the animals and plants which live- in the sea, and also with any theoretical questions upon which these animals and plants throw any light. Great biological discoveries and generalizations have been made from the study of marine animals, and some of the problems of the greatest general interest which still await solution will no doubt be worked out in the abundant and varied material which presents itself to the marine biologist. The Port Erin Station is a sea-side laboratory which enables the investigator to examine the sea-bottom lying around the Isle of Man, and to make known the conditions of existence, and the various kinds of plants and animals living in the Irish Sea.

There are four important functions which such a biological station can perform :—

(1) It can supply materials for their investigations to the Committee who have founded it, and so be a means of adding to knowledge; (2) it will enable science students from our colleges to become acquainted with marine animals in the living state and in various stages of development; (3) it may enable scientific knowledge and experiment to be applied to our sea-fisheries, and so, by sea-fish hatching and shell-fish culture, may largely benefit our important local industries; and (4) the tanks in the Aquarium will enable the general public to see something of submarine life, and to realise to some extent the interest and importance of biological studies.

The Liverpool Marine Biology Committee were fortunately able to arrange with Mr. Thomas Clague, proprietor of the Belle Vue Hotel, that he should build for them the Biological Station on the beach at the foot of the hotel grounds, an ideal spot for a sea-side laboratory. It is at one corner of the bay, near where sand and rocks meet, and at the foot of the cliff upon which the Belle Vue Hotel stands; it is connected with the highroad by means of a zig-zag gravel walk and concrete steps, and the sea comes to within a few yards of the windows of the laboratory. The Biological Station consists of two buildings, the laboratory on the south, and the aquarium on the north of the steps. The laboratory contains a main workroom capable of accommodating about six workers, and a small room for the Director, with the commencement of a Reference Library.

The Aquarium House is in two floors, the lower of which, opening off the beach, has a sea-water well communicating with the sea, and some large concrete tanks and wooden hatching boxes, while the upper has slate and plate-glass tanks and small aquaria, through all of which a constant circulation of sea-water can be maintained. In these tanks and aquaria the sea-anemones, zoophytes, star-fishes, shell-fish, and various other beautiful and interesting animals of the neighbouring seas are kept under observation, and the public are admitted on certain days and hours, a small charge being made to aid in keeping up the institution. A fuller account of the Biological Station and the work which is carried on there will be found in the Annual Report, while the detailed reports upon the marine animals and plants are given in the four volumes of ‘The Fauna of Liverpool Bay,’ already issued. Students and others wishing to carry on any work at the station should apply to the Director, Professor Herdman, Liverpool; while subscriptions and donations in aid of the funds of the institution (which is mainly supported by voluntary contributions) may be sent to the hon. treasurer, Mr. I. C. Thompson, 4, Lord Street, Liverpool.

[note fpc - the station later moved to its present position on the south of the bay]

The most favourable localities around the south end of the Isle of Man for collecting animals and plants on the shore at low tide are :—(1) Fleshwich Bay, to the north of Port Erin, where there are some excellent rock-pools; (2) the rocks on both sides of Port Erin Bay—towards Spaldrick, on the north, and between the harbour and the breakwater on the south: in the former locality there are rock-ledges and pools, and in the latter large stones to turn over;. (3) the Calf Sound, and especially the shores of the small islands called ‘The Clets,’ which can be visited readily in a boat from Port Erin or Port St. Mary at spring tides; (4) the caves near the Sugar-loaf rock, which have to be entered by boat, and which show at low-tide great areas of rock almost wholly covered with sea-anemones, zoophytes, sponges, ascidians, and other animals; and (5) the limestone reefs on the shore stretching between Port St. Mary and Perwick Bay — these have numerous pools, crevices, and broken escarpments which are well worth careful ex-ploration.

The sea around the Isle of Man is classic ground to the-marine biologist, as being the scene of the pioneer dredging work of Professor Edward Forbes more than 60 years ago. Since then, however, very little had been done in the district until the Liverpool Marine Biology Committee commenced their investigations in 1885. For dredging expeditions good ground can be obtained all along the-coast. The so-called Coralline zone, which follows on the Laminarian, the upper edge of which is just exposed at extreme low water, extends from about 5 to 40 fathomu or so, where the deep mud begins. In some spots, at about 20 fathoms, it is made up over considerable areas almost entirely of ophiuroids (Ophiocoma nigra and Ophiothrix fragilis), which fill the dredge haul after haul. At two localities off the Isle of Man, viz., along the east coast from Clay Head to St. Anne’s Head, and off the west coast between Contrary Head and Niarbyl, at depths between 10 and 20 fathoms, are great nullipore deposits formed of Melobesia and Lithothamnion, which have a most characteristic appearance and fauna.

This area of the sea-bottom, from 10 to 20 fathoms, extends across from the north of Lancashire to the Isle of Man, so that opposite Barrow, for example, there is a wide extent of about 50 miles in length of sea-floor at depths of not more than 15 or 16 fathoms (see p. 45, section). The Isle of Man is connected with England by this plateau, and is separated from Ireland by deep water.

Depths of over 20 fathoms are only found to the west, north, and south of the Isle of Man; and depths of from 20 to 50 fathoms give us the most varied bottom deposits and the richest fauna. As a rule, the sand is more or less mixed with mud, and as the bottom goes deeper the amount of mud gets greater. When there is a considerable admixture of mud with coarse sand, it forms what is known to the trawlers as a "reamy" bottom, and that is the ground upon which the sole and some other valuable fish are generally found spawning.

Shells and other hard parts of animals play an important part in the deposits at depths of about 20 fathoms and upwards. In places the dredge comes up filled with Pecten shells, dead and alive, chiefly F. opercularis and F. maximus. At other places the deposit is practically composed of the shells of Fectunculus glycimeris. These and other shell-beds form a rich collecting ground to the naturalist, as they support an abundant and varied fauna.¹ Zoophytes and polyzoa are attached to the shells, and these serve as shelter for nudibranchs and other small mollusca, worms and ascidians. On the whole the heterogeneous deposits support a richer fauna than do the homogeneous deposits, such as sand or mud, and it is chiefly in the zone of depth we are now considering that the heterogeneous deposits occur. It is from this region that the greater number of our additions to the British Fauna have come.²

A continuation of the deep-water depression (over. 50 fathoms) runs down from the Clyde sea-area, on the western side of the Isle of Man (see Chart, and Section, p. 45), and gives depths of 70 and 80 fathoms within 12 miles of land. The bottom of this depression is occupied by a stiff blue-grey clay-mud, in which we find a peculiar fauna, including the sea-pen Mirgularia mirabilis, the anemones Sagartia herdmani and Faraphellia expansa, the Echi noderms Brissopsis lyrifera, and Amphiura chiajii, the Polyzoon Triticella boeckii, the worms Fanthalis oerstedi and Lipobranchus jeffreysii, the Crustacean Calocaris macandrece, and the Mollusc Isocardia cor.

Full accounts of the marine Animals and Plants found round the Isle of Man have been published by the Liverpool Marine Biology Committee, in their volumes of the ‘Fauna,’ and complete lists up to date will be laid before Section D at this meeting of the British Association. Consequently only a brief summary will be given here.

Our marine ALGAE have been collected and worked out by Prof. Harvey Gibson, by Prof. Weiss, the Rev. T. S. Lea, and others. About 250 species in all have been recorded.

Mr. Siddall has recorded over 160 species of FORAMINIFERA for the Irish Sea, and Mr. Pearcey and Dr. Chester have brought the number up to 180 Thirteen of these were new to science.

The SPONGE fauna of the caves and rocks round the south end of the Island is rich, especially in Tetractinellids, and Dr. Hanitsch has drawn up a list of nearly 60 species.

In regard to CELENTERATA, we have on record about 90 species of zoophytes, including such interesting forms as Garveia and Corymorpha nutans. There are 36 species of Medusae, and a few Ctenophora and Siphonophora. Amongst Alcyonaria, Alcyoniurn, Sarcodictyon (both red and yellow varieties), Virgularia and Fennatula are all represented; and over 20 species of Actinians have been recorded. The abundance and beauty of the sea-anemones in some of the rocky channels and caves round the south end of the Isle of Man is celebrated amongst local naturalists.

All groups of the ECHINODERMATA are well represented in our fauna; we have 35 recorded species. Antedon, the rosy feather star, is found round the coast. We have 1 species of star fishes, amongst which Porania pulvilus, Stichaster roseus and Falmipes placenta are common in the deeper water to the west of the Isle of Man—where Brissopsis lyrfera and Amphiura chiajii are also found. We have eight species of Holothurians in all. Synaptc& inhcerens is found in muddy shingle on the shore at Port Erin, and the little Cucumaria planci, first recognised as a British species in our district, is found by dredging. .dmphiura elegans and Asterina gibbosa are abundant in the coralline pools. We find the parasitic Orthonectid 1?hopalura swarming in some of the specimens of Amphiura.

The ANNELIDS in the latest list, by Mr. J. Hornell, number 87 species; Mr. Gamble has found 26 species of TURBELLARIA, and Mr. Beaumont 22 of NEMERTINES.

Sagitta is common throughout the sea; Spadella, and the Archi-Annelids Dinophilus and Folygordius are found at Port Erin. There are various GEPHYREA, including a large green species of Thalassema, which may be new to science.

The two BRACHIOPODA Terebratula Caput serpentis and Crania anomala are both found in deep water. Miss Thornely records over 140 species of PoLYzoA, some of which are rare and interesting forms. -

Our CRUSTACEAN fauna is rich; Mr. A. 0. Walker has drawn up a list of over 240 species of Malacostraca and Amphipoda, and half-a-dozen of these were previously unknown to science.

Amongst lower Crustacea, the COPEPODA have been carefully investigated by Mr. I. C. Thompson and Mr. Andrew Scott, with such success that we have now on record over 190 species, many of which were new to science.

The MOLLUSCAN fauna is also rich, over 180 species having been recorded; one of these—A deorbis imperspicuus, Monterosata—is new to British Seas.

There are 54 species of TUNICATA known, of which three have been described as new.

We have records of about 112 species of MARINE FISH from the Irish Sea, of which 80 are from more immediately around the Manx coast. There are only a few fresh~vater fish in the streams of the island; and the Amphibian, Reptilian, and Indigenous Mammalian fauna are very scanty. I am indebted to Mr. P. M. C. Kermode for the following particulars in regard to the land biology:— There are records of 12 land MAMMALS, of which at least five have been introduced, and four species of Cetacea.

As to BIRDs: besides two escapes (probably) and two (Bitterns) extinct, we have 151 species consisting of the following orders :—Passeres 59, Picaria~ 6, Striges 3, Accipitres 6, Steganopodes 3, Herodiones 1, Anseres 16, Columbte 1, Pterocletes 1, Gallinte 3, Fulicariad 6, Limicolad 20, Gavite 12, Tubinares 2, Pygopodes 12.

A final sentence as to the land plants must conclude this very brief sketch of the Natural History of the Island, in the compilation of which much kind assistance has been received from a number of local naturalists.

Though limited, both in extent and variety, the Flora of the Island possesses considerable interest, not only as a complete subject of study within definite limits, but also as affording typical specimens from mountain and moor, marsh and glen, sandy and rocky sea-shore. The effects of the equable climate are also very noticeable in the ready and luxuriant growth, in the open, of plants which, at all events in the north of England, require the shelter of a greenhouse.

Footnotes

1 One haul of a small trawl (4-foot beam) taken on Oct. 27, 1895, off the Calf Island, at a depth of 16 fathoms, on a shelly deposit, was carefully examined and the organisms were counted. It was found that in all 156 species were represented, of which 8 species were new to science, and have since been described.

2 For further details, and for more particulars in regard to the dredging expeditions, see the article on the Marine Fauna of the L.M.B.C. district in the earlier part of this handbook, p. 43.