Rocky Shore Habitats Research Articles

Seasonal and regional variations in the feeding habits of the harbour seal, Phoca vitulina, in the Skagerrak and the Kattegat

Studies of the feeding of harbour seals have been carried out at the Tjärnö Marine Biological Laboratory since 1977. The studies are based on fish otoliths found in faeces at seal haulouts. The present paper compares feeding habitats at two different localities. Three families of fish, gadoids, pleuronectids and clupeoids were predominant in the seals' diet at a rocky shore habitat. Pleuronectids made up 75% of the diet at a sandy shore habitat. Temporal variations in feeding habits are also examined. The results indicate that harbour seals are opportunists in their choice of prey species, but some locally abundant species do not appear in their diet.

Vertical distribution of chitons (Mollusca: Polyplacophora) in the rocky intertidal zone of central Chile

The patterns of vertical distribution of chitons in various exposed rocky shore habitats of central Chile are described. The density and size of the individuals were determined at different levels on intertidal rock walls, in pools and on boulders. A group of four species was found on rock walls while another group of four species was found in tidal pools and on boulders. The species showed vertical separation on rock walls and segregation according to a range of increasing frequency of water movement in pools and on boulders. Only the two species with largest adult individuals ( Acanthopleura echinata (Barnes) and Chiton latus Sowerby) showed vertical segregation in size. Small-sized species and small individuals of large-sized species were found higher on rock walls or in zones where water movement is less; large chitons occur in zones of greatest water impact. This suggests that water movement may be a significant factor in setting the lower limits of distribution of these herbivores. Some of the species examined were extremely abundant (600·m -2) with densities of one to two orders of magnitude greater than for other chiton species elsewhere.

Bimodal respiration of intertidal pulmonates

1. 1. Aerial and acquatic rates of oxygen consumption were determined for the intertidal pulmonates Benhamina obliquata and Siphonaria zelandica at 10°C. 2. 2. There was no significant difference between the levels of oxygen consumption of Benhamina obtiquata in air and water but the aerobic metabolism of Siphonaria zeiandica was significantly reduced during submersion. 3. 3. Rates of oxygen consumption of the rocky shore pulmonates are similar to those of intertidal prosobranchs in aquatic and aerial environments. 4. 4. The ratios of aquatic to aerial oxygen consumption for pulmonates from mangrove, salt marsh, mud flat and rocky shore habitats are correlated with the presence or absence of a secondary gill.

The systematics and ecology of some cirolanid isopods from southern Japan

Summary Descriptions are given of Cirolana coronata sp. nov., Eurydice nipponica sp. nov., and C. harfordi japonica from deep water, sand, and rocky shore habitats respectively in Japan. Excirolana japonica, E. kincaidi, and E. vancouverensis, are considered to be only geographical variations of E. chiltoni which now has a circumnorth Pacific distribution. C. australiense is reported for the first time from Japanese waters, and the sub species C. harfordi japonica Thielemann is confirmed by comparison with C. harfordi harfordi Lockington from California. The ecology of the two latter species is briefly compared.

The rocky shore ecology of Sullom Voe

SynopsisThe rocky shore ecology of Sullom Voe is described from surveys carried out at 43 sites in and around the Voe. The sites were located partly to provide a description of communities from a wide variety of Shetland rocky shore habitats. Records of the species present and their distribution and abundance were based mainly on check-lists including 8 lichen, 21 algal and 23 animal taxa. Other species present at each site were usually also recorded. A total of 10 lichens, 82 algae and 91 animals were recorded during four surveys in 1976, 1977, 1978 and 1979. Differences in the distribution, abundance and vertical extent of species from site to site were associated mainly with exposure to wave action, slope of the shore and the stability of the substrate. Several species common on shores in the south of the British Isles were absent or rarely recorded in Sullom Voe or Shetland. A few species rarely found or absent in the south of the British Isles were common in Shetland. During the three years of the survey, most changes in communities present on each shore have been small. However, since 1976, the abundance of the green alga Enteromorpha sp. has shown an increase, whilst populations of the barnacle Balanus balanoides have declined. The spillage of 1,100 tonnes of fuel oil in January 1979 resulted in oiling of the upper shore at many sites but with little mortality to intertidal species except where shores had been cleaned mechanically. The Australasian barnacle Elminius modestus has been recorded from Sullom Voe but the populations are probably very sparse. It is concluded that a wide variety of rocky shore communities are present within a small area in the region of Sullom Voe, that the communities show an overall high degree of stability, but they are impoverished with respect to numbers of species compared to shores in the south of the British Isles.

Ecology ofIdoteaspp. (Isopoda) in the northern Baltic

Abstract The population dynamics and bteeding biology of Idotea baltica, I. chelipes and I. granulosa wete studied in the littoral belts of two northern Baltic rocky shore habitats. Population sizes are largest in the aurumn, after occupation of the Fucus belt by a new Idotea generation from the belt of filamentous algae. Two periods of dectease in the population density, one in late autumn and another after the breeding period in the following summer were observed. Adult males are eliminated from populations before females. Most individuals in each species breed simultaneously in eatly summer. Brood numbers are related to female size, but great marsupial mortality occurs during incubation. Idotea juveniles grow exp.nentially in late summer, but during winter the growth is delayed. Another period of intensive growth occurs in spring before breeding. I. baltica is the dominant species in both habitats examined. I. chelipes and I. granulosa were found not to coexist. The roles of different factors affecting the distribution and geographical variation in Idotea are discussed.