Intertidal Fish Research Articles

Resilience of a rocky intertidal fish community in a physically unstable environment

A 7-year census of intertidal fishes has been made by repeated defaunation of tide pools in the northern Gulf of California. The intertidal fish community showed long-term resilience and hence stability, under a rigorous, unstable physical environment. Although the majority of fishes have tropical affinities (76 %), warm temperate species (24 %) constitute 33 % of total numbers and 69 % of total biomass of the entire intertidal fish community. Short-term seasonal fluctuations in species diversity and population numbers of temperate fishes were in better synchrony with the annual light regime and sea temperature cycles than those of tropical species. A winterkill due to abnormally low sea temperatures in January, 1971, exerted faunal selection by killing several tropical fishes. Warm temperate species tolerated these low temperatures both experimentally and during the 1971 winterkill. Low sea temperatures were judged to be more limiting to diversity than high sea temperatures. The seasonal tidal pattern in the northern Gulf of California moderates summer heating but accentuates winter cooling thus favoring winterkills. We conclude that this intertidal fish community, dominated by r-selected species, is more physically controlled than biologically accommodated and the temperate species play an important rôle in regulating the stability of this fish assemblage.

Seasonal Shifts in the Spawning Site of a Northeast Pacific Intertidal Fish

In Barkley Sound, Vancouver Island, Canada, the spawning of the black prickleback, Xiphister atropurpureus, occurs during winter on rocky beaches protected from wave action. However, during spring, spawning occurs on rocky beaches of increasing exposure. This species spawns only under boulders with pebble, small rock, or shell substrates. Coincident reduction of wave action and increases in temperature probably cause the seasonal shift in the spawning site of this stichaeid.

A multidisciplinary approach to a new species of Gobius (Teleostei: Gobiidea) from southern Cornwall

The Mediterranean‐Atlantic genus Gobius L. (type G. niger L.) is redefined with listing and comparison of the 14 species currently assigned to it. A G. auratus complex of species is discussed with special reference to the real identity of the former species originated by Risso. Features of a further new species, Gobius couchi, from Helford, Cornwall, and Lough Ine, Co. Cork, are compared with those of its nearest relatives, G. auratus Risso, 1810, G. luteus Kolombatovic, 1891, and another new offshore form from the English Channel.A systematic description of G. couchi is given, including details of head lateral‐line canals and sensory papillae, and also of the karyotype (Appendix). A summary of biology covers geographical distribution, habitat and associated intertidal fishes, diet, parasites, reproduction, age‐composition, and size. The electrophoretic properties of selected functional proteins (haemoglobins, muscle‐myogens, and lactate‐dehydrogenase isozymes) are described and contrasted with those in other available neighbouring species (G. paganellus, G. niger, and Thorogobius ephippiatus). Alternative terminology for LDH patterns is discussed, and the role of protein studies considered for gobioid classification.The specific status of G. couchi relative to the Mediterranean G. auratus is reviewed, and meristic divergence between the two compared with that found among widely separated populations of G. niger which exhibit less geographical variation in these criteria. Mechanisms for allopatric speciation are discussed, and it is concluded that ancestral populations of the two forms became parted possibly at the time of the Roman regression (corresponding to the Mindel glaciation) when the Mediterranean may have been closed‐off from the Atlantic. Rates of evolution shown by European gobiids are considered in the light of Pleistocene and postglacial opportunities for reproductive isolation.

A Pirhemocyton-like parasite of the Blenny, Blennius pholis L. (Teleostei; Blenniidae) and its relationship to Immanoplasma Neumann, 1909

A light and electron microscopic study was made of a Pirhemocyton-like infection of the red blood cells of B. pholis, an intertidal fish. Electron micrographs show that polygonal particles occur in the cytoplasm of infected cells; these particles resemble the supposed icosahedral virus of Pirhemocyton. Inclusion bodies associated with the infection also resemble those seen in Pirhemocyton. Immanoplasma Neumann, 1909, was re-examined from blood films taken from three infected Scyliorhinus canicula collected in 1970. A marked similarity was noted between the inclusion bodies of the Blenny infection, Pirhemocyton and the Immanoplasma body. The nature of the numerous particles in the infected red blood cells of S. canicula is not known, therefore, Immanoplasma is only tentatively included in the group of known and suspected icosahedral cytoplasmic deoxyriboviruses.

Buoyancy in Porcellana platycheles

Intermoult Porcellana platycheles (Pennant) are slow moving, crawling crabs, incapable of swimming upwards from the substrate. Newly moulted porcelain crabs, however, are capable of effective upward swimming. An increased efficiency of tail-fan propulsion in newly moulted crabs was thought unlikely, and it was suspected that newly moulted P. platycheles were more buoyant than intermoult crabs. Results are presented to show that this is the case, and calculations were performed which indicate that fluid uptake at moult is insufficient to produce the observed increase in buoyancy. It is concluded that loss of heavy minerals and scleroprotein at moult cause the increased buoyancy. The adaptive significance of the enhanced swimming ability in newly moulted crabs is thought to lie in an improved ability to escape predation by intertidal fish and crabs.

The Vertical Distribution and Feeding Relationships of Intertidal Fish on the Atlantic Coast of France

The ecology and vertical distribution of many sessile littoral species is well known, but relatively little information is available regarding the intertidal fishes. The few papers that are wholly or partially concerned with this subject are those of Le Danois (1913) on the French coast, Gosline (1965) in Hawaii, Porumb & Porumb (1968) in the Black Sea, Zander (1967) in the Red Sea, Sasaki & Hattori (1969) on Japanese shores, and Abel (1962), Gibson (1968) and Casabianca & Kiener (1969) in the Meditterranean. The subject of the biology and behaviour of littoral fish in general has been reviewed recently by Gibson (1969). This paper presents the results of a detailed quantitative investigation into the distribution and feeding relationships of shore fish carried out in June and July 1969 in a limited area on the Atlantic coast of France.

The tidal rhythm of activity of Coryphoblennius galerita (L.) (Teleostei, Blenniidae)

The swimming activity of the intertidal fish Coryphoblennius galerita (L.) recorded in natural daylight and darkness and in complete darkness, shows a periodicity which is phased with the tidal cycle. Of the two activity peaks which occur each day, the first is usually the greatest, caused by a weak circadian component of the rhythm with a peak in the late morning. Darkness has a small suppressive effect on activity. The activity rhythm is considered to be related to feeding.

Intertidal Fishes as Food of the Common Garter Snake

Intertidal Fishes as Food of the Common Garter Snake