Use of telemetric tracking to examine environmental influences on catch/effort indices. A case study of Atlantic Salmon (Salmo salar L.)in the R. Tywi, S. Wales

A case study of Atlantic Salmon runs into the R. Tyvi (S. Wales) is presented. Radio tracking of over 200 salmon in 1988 and 1989 has demonstrated that flow is an important factor in modifying both run timing and migratory success. Entry of salmon into the river is typically in response to flow events, and periods of low falling flows delay entry and may directly result in reduced runs into the river. Delayed entry may also increase the proportion of the run migrating after the end of both rod and net fishing seasons. The implications of these results for net and rod catch and catch/effort data are discussed, using both statutory reported catch data and data from specific catch/effort studies. Flow is demonstrated to be a dominant factor in determining the within-season distribution of rod catch and catch/effort during low-flow years. Estuarial seine net catch and catch/effort tend to be controlled more by time of return than by flow although low flows may delay runs. Annual reported rod catch is correlated with flow, which controls in season availability, catchability and consequently the amount of fishing effort. Use of catch or catch/effort data should take account of inter-year variations in flow and other environmental factors. Although catch and catch/effort are valuable indicators of fishery performance, they are inadequate to represent changing stock levels.

Reference area as a factor affecting potential yield estimates of coral reef fishes

A compilation of 48 estimates of Caribbean and Pacific coral reef fish catches, ranging from 0.1 to 23.7 t km super(-2) year super(-1), obtained from coral reef areas ranging from 0.1 to nearly 4-10 super(5) km super(2), are used to show that observed catches, and hence potential yield estimates, depend strongly on the reference area. The implications for coral reef fisheries assessments are discussed.

A multivariate statistical study with a factor analysis of recent planktonic foraminiferal distribution in the Coromandel Coast of India

A study of planktonic foraminiferal assemblages from 19 stations in the neritic and oceanic regions off the Coromandel Coast, Bay of Bengal has been made using a multivariate statistical method termed as factor analysis. On the basis of abundance, 17 foraminiferal species, species were clustered into 5 groups with row normalisation and varimax rotation for Q-mode factor analysis. The 19 stations were also grouped into 5 groups with only 2 groups statistically significant using column normalisation and varimax rotation for R-mode analysis. This assemblage grouping method is suitable because groups of species/stations can explain the maximum amount of variation in them in relation to prevailing environmental conditions in the area of study.

Length-weight relationship and condition factor of black carp (Mylopharyngodon spiceus Richardson) in Bangladesh

The length-weight relationship and condition factor of Mylopharyngodon spiceus were determined. The result of the study showed the dependence of weight (W) on the total length (L) in the following form: W= 0.006L(super 3.156) or in the logarithmic form Log W=- 2.1851 + 3.156 Log L. Standard errors of length and weight were 0.674 cm and 3.214 g respectively. The co-efficient correlation "r" was found to be 0.972 which indicated that the relationship between length and body weight of the fish was highly significant. The t-test also indicated that the correlation between length and weight was significant. The range and mean value of condition factor (K) were 0.865 to 1.041 and 0.958 respectively.

Length-weight relationship and relative condition factor of pond-reared mahseer, Tor putitora(Ham.)

The study deals with the length-weight relationship and relative condition factor (Kn) of mahseer, Tor putitora reared for 150 days in ponds. The logarithmic form of equation for the relationship was found to be logW = -1.727+2.875logL or W=O.Ol875U·875 • The graphical presentation of the parabolic and logarithmic forms showed respectively the curvilinear and linear relationships between length and weight of the fish. The mean value (±sd) of relative condition factor was found to be 0.95±0.12. The exponential value 'b' was found to be 2.96 and the coefficient of correlation 'r' was 0.965, which showed strong and highly correlated relationships between length and weight of the fish.

Length-weight relationship and relative condition factor in Oreochromis mossambicus (Peters) of Bhima River

Oreochromis mossambicus (Peters), a common freshwater fish of Bhima river, has high economic value and considerable fishery importance. The length-weight relationship in the logarithmic way for this fish can be written as: Log W = - 4.50241627 + 2.884822741 log L. This is close to the cubic law indicating the isometric growth of the fish in its natural habitat. The correlation coefficient (r) was found to be 0.9865 which showed a good relationship between the two parameters. The mean relative condition factor (K sub(n)) was 1.00 suggesting the well-being of the fish.

Length-weight relationship and condition factor of Perna viridis (Linnaeus, 1758) and Meretrix meretrix (Linnaeus, 1758) from Mumbai waters

Length weight relationship of the two commercially important molluscs P. viridis and M. meretrix was found to be W=-0.40263L super(2.044719) & W=-0.04359L super(2.2315498) respectively. Condition factor was recorded to be less than 1.0 for most part of the year in P. viridis and for M. meretrix it ranged from 0.39 to 4.61. The present study reveals that there was allometric growth in both the species and the growth was not satisfactory since it showed lower K-value during most part of the year.