#EX VESSEL MEANING PLUS#

Quantity landed in turn is the result of resource availability and fishing tactics. Total revenue is the result of quantity landed and ex-vessel fish price (price fetched by fishers per kg landed fish or shellfish). This means that, assuming that extraction costs are similar for different species, revenues of species in a portfolio need to be negatively correlated. Negative correlation between economic returns of species in the portfolio is a necessary condition for a portfolio strategy to be advantageous, that is, less risky by providing more stable returns, compared to a single target strategy. Thus, if returns from the different species are negatively correlated, the portfolio return variance is smaller than the sum of species specific return variances the difference between the two variances should increase with the number of species in the portfolio.

#EX VESSEL MEANING PLUS#

If the landings are made up of several species, then, the variance of the composite return is the sum of the species return variances plus the covariance of these returns. The economic returns from fishery catches are the total revenues (also called landed value or turnover), minus the extraction costs. species connected via the food web, in such a way that the harvesting modifies the ecosystem to a desired profitable state. went a step further and proposed a portfolio approach to fisheries management which explicitly considers the trade-offs between harvesting functional groups, i.e. Fisheries management can encourage diversification of activities. Translated into the fisheries context, a portfolio strategy requires a diversity of fishing gears, fishing areas or target species at the individual fisher level.

The likelihood of this to happen should increase with portfolio diversity or width. A portfolio strategy consists in asset diversification and is likely to be advantageous when different assets change in different ways over time. advocated the application of the principles of financial portfolio management to environmental management. To guard against environmental risks, Costanza et al. In conclusion, the interannual variability of economic returns or energy ratios of French fisheries in the Bay of Biscay did not decrease with the number of species or functional groups exploited, though it varied between fleets.ДЇisheries are confronted by variability in resources and markets generating income risks. Interannual variability in total sale revenues was larger than the sum of species specific sales revenue variability, except for fleets using hooks and pelagic trawlers it increased with the number of species exploited. Energy ratio expressed by the ratio between fuel energy used for fishing and energy contained in landings varied from 0.3 for purse seines to 9.7 for trawlers using bottom trawls alone or in combination with pelagic trawls independent of portfolio width. Economic fleet returns (sale revenues minus fishing costs) varied strongly between years the interannual variability was independent of portfolio width (species or functional groups). The portfolio width of fleets ranged from 1вЂ“3 functional groups, or 4вЂ“19 species. For this, vessels were grouped into eight fishing fleets based on the gears used and exploited species were grouped into five functional groups. Using a range of indicators, these predictions were tested for the French fishing fleets in the Bay of Biscay (Northeast Atlantic) during the period 2001вЂ“2009. Also, variability is expected to decrease with portfolio width. According to portfolio theory applied to fisheries management, economic returns are stabilised by harvesting in a portfolio stocks of species whose returns are negatively correlated and for which the portfolio economic return variance is smaller than the sum of stock specific return variances.

Ex vessel meaning