M F M F

Mean (tr.) numbers 0.024 0.016 0.129 0.124 0.348 0.207 1.693 1.809 0.211 0.159 0.830 0.851 F P variance were very small (0.72 , 4.84 and 0.54 , respectively) compared with other variables such as season, station and age of the trout. Table 26 shows that although the female trout in the sample are significantly longer than the males and also have a tendency to be heavier, their mean condition factor was significantly less than that of males. Unlike the trout there were no significant differences...

Info

Abundant in 1943 (Jones, 1943) and in 1950 (Thomas, 1958a, b,1964b, c). Note 1981 values based on Jenkins et al. (1984) Abundant in 1943 (Jones, 1943) and in 1950 (Thomas, 1958a, b,1964b, c). Note 1981 values based on Jenkins et al. (1984) Awachie (1968), were overdispersed and present at very low densities in the depositing sediments (Figures 21 and 22). The occurrence or abundance of other potential intermediate hosts for helminth parasites has also changed since 1950 or 1981. Thus, Asellus...

Fish Parasites as Sources of Information on Pollution

As stated above it is difficult to use parasites as bioindicators of pollution because of the complexity and variability of their interrelationships with the environment. Despite these limitations various parasitologists have suggested that they may have some informational value as bioindicators of the following forms of pollution. Heavy metal pollution. As heavy metals often bioaccumulate at higher concentrations in the parasites than in their fish hosts several authors (Riggs and Esch, 1987...

Ecological Relevance and Density Dependence

The important question of whether populations of helminth parasites of fish are regulated in a density-dependent manner and whether they conform to the 'r' or 'K' strategies has been widely discussed (Kennedy, 1974, 1977 Holmes et ai, 1977 Esch et al., 1977 Kennedy and Rumpus, 1977 Figure 1). In order to resolve this question entomologists and fishery biologists have resorted to using 'K' factor analyses (Elliot, 1994). Unfortunately, the complexity of the infrapopulation, component population...

Ne

Figure 19 The percentage prevalence values for the major parasites and total parasites of the brown trout in 1998. DS, D. sagittatcr, CF, C. farionis CM, C. metoecus PS, P. simile NR, N. rutili NE, nematodes. Knudsen et al., 1997) as well as sex bias in the parasitism of trout and other species like the three-spined stickleback (Reimchen and Nosil, 2001). Changes in the food webs attributable to environmental stress, such as increased acidity (Marcogliese and Cone, 1996), competition for food...

Parasitic Fauna

LARGER GAPE MANDIBLES EXTEND TO POSTERIOR MARGIN OF EYE BODY STOCKIER CAUDAL PEDUNCLE THICKERAND CAUDAL FIN LESS INDENTED TEND TO OCCUPY MID-WATER POSITION IN LAMINAR FLOW TERRITORIES INCLUDE POOLS, BACKWATERS AND SLACK WATERS UNDER BANKS DIET HAS HIGHER 'S OF Lymnaea, Sphaerium, Asellus, Gammarus, and ammocoete LARVAE ASSOCIATED WITH DEPOSITING SEDIMENT, WHICH ACT AS INTERMEDIATE HOSTS PREVALENCES AND ABUNDANCE VALUES FOR D.sagittata, C.farionis, C.metoecus, P.simile, N.rutili, R.acus and...

Physicochemical Factors that may Influence the Distribution and Abundance of the Parasites and their Fish Hosts

The nature of the parasitic community in aquatic ecosystems is determined by interactions involving the definitive host fish, the intermediate hosts and the physicochemical factors (Wisniewski, 1958 Dogiel, 1961 Chubb, 1970 Kennedy, 1978c Esch et al, 1988 Kennedy and Hartvigsen, 2000). The major physicochemical factors that may influence the distribution and abundance of the parasitic fauna in aquatic ecosystems are summarised in Table 4 and Figure 1 and their possible involvement is discussed...

Months

Figure 9 Seasonal changes in the condition factor ( 95 C.L.) of the salmon parr over a 12-month period. chief factors affecting growth when food is not limiting gave an excellent fit to the data. During the course of the present investigation on the Teifi it was found that the water temperatures were favourable for growth from mid-April until September (Thomas, 1962). This period coincided with the time when the condition factors of the trout reached maximum values (Figure 8) and when their...

Advances In Parasitology Vol 52 0065308x

Copyright 2002 Elsevier Science Ltd All rights of reproduction in any form reserved 6.3. Statistical analyses of the relationships between parasite abundance and the condition factor and adipose index 61 6.4. Reasons for the absence of harmful effects due to parasites 70 6.5. Reasons for some parasites causing detrimental effects 70 7. Sex Bias in Parasitism and Causative Mechanisms 74 7.2. An evaluation of the Hamilton-Zuk and immunocompetence 75 8. The Helminth Fauna of Trout and Salmon Parr...

Statistical Analyses of the Relationships between Parasite Abundance and the Condition Factor and Adipose Index

As the regression equation, based on a plot of loge weight against loge length for trout, was y -4.17973 2.87876x the value of 2.87876 was used to calculate the condition factor W L2-87876 .100, where W the weight in grams and L the length in cm. Figure 8 shows that the condition factor varies significantly P lt 0.001 on a seasonal basis with the values rising from April until August or September after winter lows and then declining during the spawning and post-spawning period from October to...

Regression Plot

Figure 14 The relationship between the condition factor of the trout a and the salmon parr b and the total parasite abundance transformed log10 1 x . As the regression equation, based on a plot of loge weight against loge length for the salmon parr was y -3.79918 2.76135x the value of 2.76135 was used to calculate the condition factor W L2-76135 . 100 where W the weight in grams and L - the length in cm. Unlike the brown trout the condition factor showed no significant seasonal variation...

Co

Salmo spp., Onchorhynchus, Coregonus, Salvelinus, Prosopium Kennedy, 1978 Hoffman, 1998 Species of Coregonus, Salmo, Salvelinus, Thamallus, Perca, Etheostoma, Lepomis, Lota, Leucichthys, Notropis, Oncorhynchus Cristivomer, Prosopium, Gasterosteus Hoffman, 1998 . First intermediate host Pisidium sp Sphaerium corneum Brown, 1927, Hoffman, 1998 , Pisidium casertanum, Poli Awachie, 1968 . Hopkins 1934 suggested that due to widespread distribution of this species, it may adapt to other invertebrate...

Comparative Aspects

At the ecological level the heminth parasites common to both the trout and salmon parr share many spatial and temporal patterns. Thus, C. metoecus exhibit summer troughs and winter highs, unlike N. rutili, in both fish species. However, the abundance of C. farionis does not vary seasonally in the case of salmon parr although it does so in the trout. Likewise D. sagittata and N. rutili are more abundant in both trout and salmon parr at Station A than at Station B. As with trout there were...