Mersey Estuary saltmarsh vegetation survey 2002

This is the Mersey Estuary Saltmarsh vegetation survey 2002 report produced by the English Nature Cheshire in 2003. This report looks at the mapping of vegetation communities on the saltmarsh of the Mersey Estuary. The total area of saltmarsh and associated communities within the Mersey Estuary was found to be 724.1 ha. Most of the saltmarsh in the Mersey Estuary is presently ungrazed or only very lightly grazed, creating a very rank sward in excess of 20 cm in height which is not generally suitable for grazing or roosting birds. On the northern side of the Mersey Estuary, the saltmarsh around the Hale Decoy was lightly grazed by horses, but the remainder was ungrazed. On the south side, the saltmarsh was fairly heavily sheep-grazed along the Frodsham Score, very lightly grazed at Ince Banks by sheep straying from Frodsham and ungrazed at Stanlow Banks. Despite much of it presently being ungrazed, the saltmarsh of the Mersey Estuary is relatively poor in plant species. It appears that this is because the ungrazed areas have been so for less than 20 years and have thus not had time to develop the diversity of a long-established ungrazed marsh. However, withdrawal or depletion of grazing has produced a rank sward which is less valuable to grazing and roosting birds.

James's rule and causes and consequences of a latitudinal cline in the demography of John's Snapper (Lutjanus johnii) in coastal waters of Australia

Demographic parameters were derived from sectioned otoliths of John’s Snapper (Lutjanus johnii) from 4 regions across 9° of latitude and 23° of longitude in northern Australia. Latitudinal variation in size and growth rates of this species greatly exceeded longitudinal variation. Populations of John’s Snapper farthest from the equator had the largest body sizes, in line with James’s rule, and the fastest growth rates, contrary to the temperature-size rule for ectotherms. A maximum age of 28.6 years, nearly 3 times previous estimates, was recorded and the largest individual was 990 mm in fork length. Females grew to a larger mean asymptotic fork length (L∞) than did males, a finding consistent with functional gonochorism. Otolith weight at age and gonad weight at length followed the same latitudinal trends seen in length at age. Length at maturity was ~72–87% of L∞ and varied by ~23% across the full latitudinal gradient, but age at first maturity was consistently in the range of 6–10 years, indicating that basic growth trajectories were similar across vastly different environments. We discuss both the need for complementary reproductive data in age-based studies and the insights gained from experiments where the concept of oxygen- and capacity-limited thermal tolerance is applied to explain the mechanistic causes of James’s rule in tropical fish species.

Capturing views of men, women and youth on agricultural biodiversity resources consumed in Barotseland, Zambia

This paper presents data and findings from focus group discussions in study communities selected by the CGIAR Research Program on Aquatic Agricultural Systems (AAS) in the Western Province of Zambia. The discussions focused on cultivated crops and vegetables collected from open fields and consumed as food. Participatory tools for agricultural biodiversity (agrobiodiversity) assessment were used to capture community perspectives on plant species and varietal diversity; factors influencing the availability and use of plants for food; unique, common and rare crop species cultivated in a community, identified through a four-cell analysis methodology; and core problems, root causes, effects and necessary actions to tackle them, using problem tree or situation analysis methods.