Lion's paw scallop (Nodipecten subnodosus, Sowerby 1835) aquaculture in Bahía Magdalena, Mexico: effects of population density and season on juvenile growth and mortality

This study examined the effects of density and growing season on growth and survival of juvenile lion's paw scallops (Nodipecten subnodosus) in Estero San Buto, a mangrove channel in Bahía Magdalena, Mexico. Scallops were kept in plastic mesh bags in oyster trays at three population densities (500, 1000 and 2000 organisms per tray, or low medium and high density respectively) over a period of 2 months from October to December 2001 and from February to April 2002. Growth (shell height increment) was measured every 7–12 days and mortality was evaluated at the end of the experiment (dead shell count). Overall growth was fast (0.24–0.38 mm day^?1) in comparison with other pectinids. Significant differences were found for both, density and season, with faster growth occurring at lower densities and during the fall season when the water temperature was higher. Mortality was low (0.5–3.0% 60 day^?1) except for the high‐density treatment in the fall (44% 60 day^?1). Crowding together with high water temperatures and increased metabolic oxygen demand of the scallops and possibly competition for food were the probable reasons for this high mortality. Overall, mortality was lower in the spring, when temperatures were lower, O₂ values were higher and food was more abundant.     

生物有机肥对墨西哥玉米饲用价值的影响

研究了4个浓度的生物有机肥（0、50、60和70 kg·667m-2）对墨西哥玉米（Zea mexicana）生长特性与牧草养分和饲用价值的影响。结果表明,随施肥浓度的增加,墨西哥玉米的叶长、株高、鲜干草产量、粗蛋白（CP）、粗脂肪（EE）、干物质消化率（DDM）、随意采食量（DMI）和相对饲用价值（RFV）均呈增加趋势,而其粗灰分（CA）、酸性洗涤纤维（ADF）和中性洗涤纤维（NDF）均呈降低趋势。     

The Management of Small Diameter,Lesser-Known Hardwood Species as Polewood in Forest Communities of Central Quintana Roo,Mexico

ABSTRACT

Diversification in resource management can serve as a strategy to increase both economic well-being and environmental sustainability in rural communities, especially in tropical forested regions. This paper documents and analyzes the recent and rapid regional commercialization of small diameter, lesser-known tropical hardwood species as polewood in Quintana Roo, Mexico, presenting the promises and perils for sustainable management and resource diversification in the context of Mexican economic development and community forestry. We present data from interviews with local farmers and forestry officials involved in community management of timber resources to reveal baseline information regarding the use and management of polewood, locally called palizada. We found the same permitting system used for high-value timber was implemented for polewood without recognizing the complex ecological characteristics of polewood and the different metrics by which polewood and high-value timber are bought and sold. These factors, coupled with an unstable market for this new forest product and potential for overexploitation, present a difficult situation for the sustainable management of polewood. We conclude that incorporating local ecological knowledge in devising polewood management strategies can strengthen local governance and is an essential aspect of managing this emerging market of forest products.     

Variation in Guard Cell Size,Interstomatal Spacing and Stomatal Frequency in Longleaf Pine Along Latitudinal and Longitudinal Gradients

Abstract

Longleaf pine, Pinus palustris, exhibits variation in size of guard cells, interstomatal distance, and to a lesser extent stomatal distribution per unit area of needle. These morphogenetic characteristics follow the north-south and east-west distributions of the species. Thus, guard cell size increases from north to south and west to east. On the north-south distribution, longleaf pine of North Carolina origin exhibits smaller guard cells than longleaf pine of South Carolina, Georgia and Florida origins while longleaf pine of Texas origin has smaller guard cells than those of Louisiana, Mississippi, Alabama and Georgia origins on the east-west distribution. On the other hand, interstomatal space decreases from north to south and west to east. On the north-south distribution, longleaf pine of North Carolina origin has larger interstomatal space than longleaf pine of South Carolina, Georgia and Florida origins while longleaf pine of Texas origin has larger interstomatal space than those of Louisiana, Mississippi, Alabama and Georgia origins on the east-west distribution. Stomatal concentration per unit area of needle exhibits a pattern that also trails the north-south and east-west distributions of the species. The pattern indicates that stomatal frequency on the needles of longleaf pine decreases from north to south and west to east.     

The sunflower (<Emphasis Type="Italic">Helianthus annuus</Emphasis>) in Mexico: further evidence for a North American domestication

I have concluded that my initial verification of a specimen recovered from the San Andrés archaeological site in Mexico as domesticated sunflower was incorrect. The specimen in question is most likely the seed of a bottle gourd. As yet there is no compelling evidence that the sunflower was grown as a food crop in Mexico prior to European contact. In addition, the complete absence of any early historical record for the sunflower in Mexico argues against its presence in pre-Columbian times. Although no dates or boundaries can be set, the wild sunflower may have grown in northernmost Mexico in early times. A southward range expansion for the species is probably very recent, perhaps in the last few hundred years with the development of a modern road system. The widely used common names of the sunflower in Mexico are in Spanish or with Spanish words in them, which suggests that the sunflower is a post-contact arrival.

Community Forestry Enterprises in Mexico: Sustainability and Competitiveness

Community-based forest management, such as Community Forest Enterprises (CFEs), has the potential to generate positive socioenvironmental and economic outcomes. We performed a detailed survey of financial and production parameters for 30 of the approximately 992 CFEs in Mexico in order to estimate costs, income, profits, and sustainability of harvest levels for forest management, harvest, and sawmilling. Fourteen of the 30 CFEs harvested more timber than they grew in 2011, suggesting issues with sustainability, but only two of these had harvest far above annual growth, and five of those were only a fraction more than annual growth. All of the 30 CFEs except one made profits in forest management and timber growing. For timber harvesting, 22 of 30 CFEs made profits, but the losses were small for the other CFEs. For the 23 CFEs with sawmills, 18 made profits and five had losses; the greatest returns for the CFEs accrued to those with sawmills for lumber production. On average, the CFEs surveyed had high costs of production relative to other countries, but the CFEs were still profitable in national lumber markets. If Mexico were to begin importing large amounts of lumber from lower cost countries, this could pose a threat to CFE profitability.     

Prevalence of the Dirofilaria immitis infection in dogs from Merida, Yucatan, Mexico

The aim of the present study was to estimate the prevalence of Dirofilaria immitis infection, and to examine the relationship between host factors (gender, age and breed) and D. immitis infection in dogs. The study was designed as a cross-sectional study. A total of 676 dogs were examined for D. immitis infection. Adult worms (necropsy) and blood samples were collected from all animals for diagnosis of D. immitis. Blood samples were examined using a modified Knott's and thick drop techniques. Fifty-six of 676 dogs were diagnosed infected with D. immitis. The odds of infection were 2.85 times higher in female dogs, compared to male dogs (OR = 2.85, 95% CI = 1.5-5.5, P = 0.01). In addition, the odds of infection were 2.11 times higher in > or =3 years old dogs, compared with younger dogs (OR = 2.11, 95% CI = 1.1-4.2, P = 0.03). This information is important for a better understanding of the epidemiology of D. immitis in dogs in Yucatan, Mexico.     

Multidecadal otolith growth histories for red and gray snapper (Lutjanus spp.) in the northern Gulf of Mexico,USA

Dendrochronology (tree‐ring analysis) techniques were applied to develop chronologies from the annual growth‐increment widths of red snapper (Lutjanus campechanus) and gray snapper (Lutjanus griseus) otoliths sampled from the northern Gulf of Mexico, USA. Growth increment widths showed considerable synchrony within and across species, indicating that some component of environmental variability influenced growth. The final, exactly dated red snapper chronology continuously spanned 1975 through 2003, while the gray snapper chronology continuously spanned 1975 through 2006. To determine baseline climate‐growth relationships, chronologies were compared to monthly averages of sea surface temperatures, U winds (west to east), V winds (south to north), and Mississippi River discharge. The gray snapper chronology significantly (P < 0.01) correlated with winds and temperature in March and April, while the red snapper chronology correlated with winds in March. Principal components regression including springtime winds and temperature accounted for 28 and 52% of the variance in the red and gray snapper chronologies, respectively. These results indicate that snapper growth was favored by warm sea surface temperatures and onshore winds from the southeast to the northwest in March and April. Overall, this study provides preliminary, baseline information regarding the association between climate and growth for these commercially important snapper species.