Nocturnal fish movement and trophic flow across habitat boundaries in a coral reef ecosystem (SW Puerto Rico)

Few studies have quantified the extent of nocturnal cross-habitat movements for fish, or the influence of habitat adjacencies on nutrient flows and trophodynamics. To investigate the patterns of nocturnal cross-boundary movements of fish and quantify trophic connectivity, fish were sampled at night with gillnets set along the boundaries between dominant habitat types (coral reef/seagrass and mangrove/seagrass) in southwestern Puerto Rico. Fish movement across adjacent boundary patches were equivalent at both coral reefs and mangroves. Prey biomass transfer was greater from seagrass to coral reefs (0.016 kg/km) and from mangroves to seagrass (0.006 kg/km) but not statistically significant, indicating a balance of flow between adjacent habitats. Pelagic species (jacks, sharks, rays) accounted for 37% of prey biomass transport at coral reef/seagrass and 46% at mangrove/seagrass while grunts and snappers accounted for 7% and 15%, respectively. This study indicated that coral reefs and mangroves serve as a feeding area for a wide range of multi-habitat fish species. Crabs were the most frequent prey item in fish leaving coral reefs while molluscs were observed slightly more frequently than crabs in fish entering coral reefs. For most prey types, biomass exported from mangroves was greater than biomass imported. The information on direction of fish movement together with analysis of prey data provided strong evidence of ecological linkages between distinct adjacent habitat types and highlighted the need for greater inclusion of a mosaic of multiple habitats when attempting to understand ecosystem function including the spatial transfer of energy across the seascape.

Age and growth of the blue shark (Prionace glauca) in the North Atlantic Ocean

Age and growth estimates for the blue shark (Prionace glauca) were derived from 411 vertebral centra and 43 tag-recaptured blue sharks collected in the North Atlantic, ranging in length from 49 to 312 cm fork length (FL). The vertebrae of two oxytetracycline-injected recaptured blue sharks support an annual spring deposition of growth bands in the vertebrae in sharks up to 192 cm FL. Males and females were aged to 16 and 15 years, respectively, and full maturity is attained by 5 years of age in both sexes. Both sexes grew similarly to age seven, when growth rates decreased in males and remained constant in females. Growth rates from tag-recaptured individuals agreed with those derived from vertebral annuli for smaller sharks but appeared overestimated for larger sharks. Von Bertalanffy growth parameters derived from vertebral length-at-age data are L∞ = 282 cm FL, K = 0.18, and t0 = –1.35 for males, and L∞ = 310 cm FL, K = 0.13, and t0 = −1.77 for females. The species grows faster and has a shorter life span than previously reported for these waters.

Evidence for changes in large-scale upwelling in the California Current over the past 700 years [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Bidecadal radiocarbon measurements on tree rings provide a detailed series of carbon-14 activities at isotopic equilibrium with atmospheric carbon dioxide. ... Most marine environments do not permit development of a comparable series of carbon-14 ages with which to compare the terrestrial tree ring series. However, we have recently begun work on such a series using material from the varved sediments of the Santa Barbara Basin off southern California. ... We now have a nearly continuous record of carbon-14 dates representing the age of the water over the upper 100 meters. ... The ocean reservoir ages show an increase prior to 1450 and a progressive decrease with time after 1450. Although there may be other explanations, we believe this trend is principally the result of changes in large-scale upwelling of water from below 500 meters. These changes were probably also associated with changes in the intensity of the California Current.

Biodeterioration of wooden boats: a major problem facing marine fisheries

In India, the fishing industry alone incurs an annual loss of over 120 million rupees on account of biodeterioration of wooden fishing craft. None of the timber species, currently in demand for boat-building, possesses an natural bioresistance and will be completely destroyed within 6 to 12 months. Preventive measures against biodeterioration range from application of several indigenous formulations to metallic sheathings and pressure impregnation of wood with preservative chemicals. These methods do not provide lasting protection, as each has its own short-comings and inadequacies. The need for long-term research in the field of marine biodeterioration for improving the efficiency of currently known control measures, with emphasis on application of non-polluting biological methods, is stressed.