No abstract

Although Mexico has a well-established legal framework regulating fisheries for the green abalone Haliotis fulgens and pink abalone H. corrugata, there is empirical evidence about a sizeable abalone black market and substantial sectors of fishing communities dedicated to poaching. An investigation was conducted about abalone poaching in a bay located off the Baja California Peninsula, Mexico. The main objective was to determine how poaching is perceived by abalone fishermen, particularly the attitudes of legal and illegal fishing groups and the factors that determine their perception of poaching. Abalone fishermen's perceptions and attitudes about poaching seem to be conditioned by a small number of factors that were identified through a discriminant analysis (e.g., deep-seated practices and knowledge about abalone fisheries; between-group violence; and the likelihood that a given poaching work day will fail due to capture by authorities, confrontation by legal fishermen, or insufficient abalone harvest). This investigation provides an indirect exploration of the abalone poaching phenomenon and the factors underlying this practice.

The Baja California abalone is one of the most important Mexican fisheries because of its high economic value. Despite strong management efforts, this fishery has faced dramatic fluctuations attributed mainly to overfishing and variability of the marine climate. In this report we analyze sea temperature variability off Bahía Asunción, Baja California Sur (Mexico), at temporal scales that may affect abalone biological processes, such as mortality, reproduction, recruitment, and individual growth rate. Since the analysis is based on different data sources, we conducted a series of correlation analyses to determine the coherence between them. We report the average daily cycle and its variations throughout the year and between years for the period 1997–2000, the seasonal cycle and interannual deviations for the period 1992–2000, the behavior of the decadal scale variability based on annual values for the period 1959–1997, and the long-term trends after analyzing the entire 20th century. Furthermore, we conducted a spectral density analysis to estimate the proportional contribution of each temporal scale to the entire variability signal. Results from the high-frequency variability (daily to interannual) suggest a relationship between temperature and the abalone reproductive cycles, a potential negative effect of the very strong ENSO events on the postlarvae, and a differential effect of temperature on juveniles of different species. Regarding the low-frequency variability (decadal to century), we show that recent years represent a much warmer period compared to previous decades, suggesting a different biological community structure between periods. The spectral density analysis indicates seasonal variability as the major contributor to the regional variability, followed by the interannual (related to ENSO). There is almost no information of the marine climate in this region, particularly in regard to fine and high-resolution observations. This contribution will provide new quantitative elements for studies dealing with the ecology of these coastal productive systems.

In this paper, we present an incremental clustering algorithm in the logical combinatorial approach to pattern recognition, which finds incrementally the β0-compact sets with radius α of an object collection. The proposed algorithm allows generating an intermediate subset of clusters between the β0-connected components and β0-compact sets (including both of them as particular cases). The evaluation experiments on standard document collections show that the proposed algorithm outperforms the algorithms that obtain the β0-connected components and the β0-compact sets.

No abstract