Incidental Species Research Articles

Accuracy of species and abundance minimal areas determined by similarity area curves

A new method for estimating the accuracy of a representative ecological sample (species minimal area and abundance minimal area determined by similarity area curves) is presented. Formulas are derived to calculate the adequate similarity level (IS, respectively IK) in relation to the desired accuracy of the sample: IS=2 w/1+w for qualitative similarity and ≧K=2 x/(1+x)(1+y) for quantitative similarity, where w=desired qualitative accuracy of the sample, x=desired quantitative accuracy of the sample, y=abundance proportion of rare species. Based on samples from a low diversity environment in the supralittoral fringe of rocky shores (“black zone”), the new approach was tested and led to the following results: (1) Similarity area curves are an objective method to calculate the minimal area and to test the accuracy of the sample size chosen. (2) A large presample is necessary to calculate the minimal area. (3) The size of minimal area is subject to seasonal and regional variations. (4) Incidental species lead to an overestimation of the species minimal area. (5) Highly dominant species lead to an underestimation of the abundance minimal area.

Population dynamics and production studies of species of centropyxidae (Testacea, Rhizopoda) in an aspen woodland soil

Summary Twelve species of Centropyxidae and 1 species of Plagiopyxidae were observed as live cells or empty tests throughout the study period in an aspen woodland soil. Only 3 centropyxid species were considered constant and comprised 4% of the mean annual abundance, 19% of the mean annual biomass, 2 % of the total production numbers and 10.5 % of the total secondary production for all species of Testacea. Including the total production biomass for C. sylvatica , an incidental species, the total centropyxid production for the year increased to 20 % of the total testacean production. For the Centropyxidae, mean annual biomass and total annual production were measured as 0.14 and 41.1 g wet weight · m−2 respectively, while total annual ingestion, respiration losses and egestion losses were calculated as 274, 68.5 and 164.4 g · m −2 respectively. The annual production biomass varied from 115 to 225 times (mean 160) the standing crop of Centropyxidae in all the soil layers. The dry weight of carbon respired annually by the centropyxids was estimated as 3.22 g · m −2 , which amounted to 1.2 % of the total annual carbon input.

A survey of the parasites of walleye pollock (Theragra chalcogramma) from the northeastern Pacific Ocean off Canada and a zoogeographical analysis of the parasite fauna of this fish throughout its range

The results of a survey of the parasite fauna of walleye pollock (Theragra chalcogramma) collected off British Columbia during September 1978 to September 1979 are presented. Forty-three species of parasites (5 Protozoa, 2 Monogenea, 12 Digenea, 9 Cestoda, 6 Nematoda, 4 Acanthocephala, 4 Copepoda, and 1 Isopoda) are reported from examination of 312 pollock. Among these are eight species previously unreported from pollock (Zschokkella hildae Auerbach, 1910; Entobdella pugetensis Robinson, 1961; Copiatestes filiferus (Leuckart in Sars. 1885); Lecithophyllum botryophorum (Olsson, 1868); Prosorhynchoides basargini (Layman, 1930) metacercaria; Bolbosoma caenoforme (Heitz, 1920); Lepeophtheirus paulus Cressey, 1969; and Rocinela belliceps (Stimpson, 1864)). Analysis of the abundances, geographical distributions, and host specificities of the 65 parasite species reported from walleye pollock throughout its range reveals a preponderance of helminths, among them many larval forms, which are ubiquitous to marine fishes throughout much of the North Pacific basin. The parasite fauna of pollock is also characterized by a paucity of host-specific forms and by the occurrence of a large number of incidental species, a reflection of the broad feeding habits of this pelagic fish.

Responses ofIpomoeaspp. andCassiaspp. to Preemergence Applied Herbicides

Responses of six morningglories (Ipomoeaspp.) and twoCassiaspp. to 13 preemergence applied herbicides were determined at two locations in southern Alabama. Pitted (I. lacunosaL.), cypressvine (I.quamoclitL.), and willowleaf morningglories (I. wrightiiGray) were readily controlled with metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one]; entireleaf [I. hederacea(L.) Jacq. var.integriusculaGray], tall [I. purpurea(L.) Roth.], and ivyleaf morningglories [I. hederacea(L.) Jacq.] were not controlled. Norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone] controlled cypressvine morningglory, but did not adequately control the other morningglory species. Perfluidone {1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl] methanesulfonamide} gave acceptable control of cypressvine and willowleaf morningglories, but gave poor control of other morningglory species. Sicklepod (C.obtusifoliaL.) was controlled better than coffee senna (C.occidentalisL.) with 2.2 kg/ha diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and 2.2 kg/ha cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl]amino]-2-methylpropionitrile} controlled sicklepod better than coffee senna at one location each. Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] was more effective in controlling coffee senna than sicklepod. Induction of population shifts toward incidental species of these genera seems unlikely based on the herbicides included in these experiments. In most cases the incidental species were more readily controlled than the prominent weed species.

Some Epipelagic Fishes of the North Pacific Ocean, Bering Sea, and Gulf of Alaska

Abstract In the course of salmon gill-netting operations in the North Pacific Ocean, Bering Sea, and Gulf of Alaska over a 7-year period, 37 species of fishes other than salmon have been captured incidentally. The catches of such species are listed by area and their relative abundance is calculated. Compared to salmon in the same localities, the incidental species are taken in small numbers and over limited ranges. Three species have heretofore been considered quite rare, another has been seen previously only in the South Pacific, and one may represent a new species. Several fishes show seasonal variations in distribution, possibly related to a preference for warmer water.

A method of assessing the physical condition of insect-damaged grain and its application to a faunistic survey

A method of assessing the physical condition of grain residues is described. It consists of utilising data obtained by taking the weight and volume of samples before and after sieving over a 1/10-inch mesh.The application of this method to a survey of the insect population of wheat residues beneath the floor of a small granary in southern England is described. Information from the weight and volume data obtained enabled the samples to be classified in a manner agreeing with visual estimates. It had the advantage of objectivity.Three vertical series of samples were taken and analysed, and the insects present counted and identified. The size, composition and distribution of the insect population is briefly discussed in relation to the condition of the residues and their depth below the surface. The fauna consisted of grain pests (Sitophilus granarius (L.), Oryzaephilus surinamensis (L.), Ptinus tectus Boield., P. fur (L.) and Hofmannophila pseudospretella (Stnt.)) and incidental species (fungus feeders and ground-dwellers) and the two groups differed in their distribution and in their apparent response to the physical conditions.