Abundancia y estructura poblacional de la almeja roñosa Chione californiensis (Broderip, 1835) en el sistema lagunar Altata, Navolato, Sinaloa, México

Abstract

The population density and abundance of Chionecaliforniensis (Broderip, 1835) was studied in Bahia Altata (Navolato, Sinaloa, Mexico) during the period from January 2010 to January 2011. The study period was characterized by a wide variation in water temperature, which fluctuated between 21°C and 35°C (during winter and summer), and a relatively high primary productivity. The population variable of density was observed for the bank La Barrita (LB) of 30.63 ± 3.95ind/m2, La Islita (LI) 9.38 ± 0.63ind/m2 and the bank La Palmita (LP) 28.84 ± 2.17ind/m2. At the same time, a decrease in abundance was observed due to the continued exploitation of the resource within the lagoon system. The size interval of the bank LB was from 26 to 36mm, LI from 38 to 60mm and LP from 44 to 50mm.The size distribution was unimodal for the LB bank and bimodal for the LI and LP banks, with the incorporation of juveniles (small sizes) to the population of 24mm total length in the three banks. The length-weight relationship were of a potential type with a positive allometry (>3.0). The Growth rate (mm/month) for LB was 0.89 mm/month, LI was 1.63mm/month and LP was 2.23 mm/month. The analysis of population dynamics showed a growth rate relatively high with a K of 0.34 years-1 and a L of 71.44mm. The mortality rate, due to natural events and due to the fishing industry of Z was equivalent to 0.38 years-1 which was equivalent to between 50 and 60% of the exploitation. The evidence, thus, suggests that the species is mildly exploited. With respect to the physiological condition index, the LB bank was much different than the LI and LP banks, thus, at the end, presenting major percentages between 25 and 30% of the dry tissue relationship. There were no differences in the type of soil within the three banks. The soil consisted, mainly, of fine grains of approximately 125um. However, the quantity of organic matter was greater in LI and consisted of between 0.29 and 1.42%. Meanwhile, the organic matter within LP was between 0.23 and 1.33%. Lastly, LB presented the least percentage of organic matter with 0.25 to 0.67%. The median length in the size of first maturity was 32.7mm. It was observed that the bank La Palmita was the only bank that could be exploited all year round, compared to the other banks La Barrita and La Islita. The type of sediment did not directly interfere with the distribution of the clam as opposed to the organic matter which played a fundamental role in obtaining larger sizes of the organisms. The study yielded an understanding of biological and fisheries mechanisms that are important to the development of an effective and sustainable fisheries management plan