An odometre for underwater transects

A simple device for the measurement of length (or area) along an underwater transect is described. This instrument is pushed or pulled by SCUBA divers along lake or river bottoms and the rotation of a paddle wheel is recorded on a digital counter. The device eliminates the need for straight line and smooth bottom transects, and allows for greater versatility than that provided by the more usual rope line transect.     

Freshwater fishes of northern South America: a need for field guides

The efficient collection of fishes from structurally complex environments (e.g., coral reefs, kelp forests) is difficult because conventional collecting methods generally cannot be used and many of the fishes are mobile and active. We describe the design, operation, and application of a diver-propelled net for efficiently collecting many species of benthic fish that reside on coral reefs and on kelp-forested rocky reefs. The overall size of the net and mesh size of the netting can be adjusted according to the size and behavior of targeted species to minimize drag and damage to specimens. Altering these dimensions combined with proper use of the net can result in a high rate of capture success. This revised version was published online in July 2006 with corrections to the Cover Date.     

A video and photographic study of aggregation,swimming and respiratory behaviour changes in the Grey Nurse Shark (Carcharias taurus) in response to the presence of SCUBA divers

The Grey Nurse Shark (Carcharias taurus) is a popular attraction for shark eco-tourism using SCUBA. The species is also ‘globally Vulnerable’ (IUCN 2008. List of Threatened Species. www.iucnredlist.org/). Magic Point (off Maroubra) in Sydney is favoured by recreational SCUBA divers wishing to observe these sharks. The objective of this study was to experimentally test the level of the activities of recreational SCUBA divers on shark behaviour. This study assessed the shark responses to diver group size (4, 8 and 12), time of day (am, noon and pm) and diver distance from the sharks (3?m and 6?m). The study found that diver activity does affect the aggregation, swimming and respiratory behaviour of sharks at this site, albeit at short-term levels. Diver group size had no significant effect on shark aggregation, but the proximity of divers to the sharks was crucial. Shark distribution in the cave changed significantly in the presence of divers at 3?m distance from the cave, but stayed unchanged at 6?m. This was particularly apparent in the presence of large groups of 12 divers at 3?m distance when sharks increased their swim speed and ventilation mechanism from ‘active’ to ‘RAM’ ventilation. Such change coincided with a sudden decrease in ventilation frequency. Our research suggests that these effects are short-term and that sharks resume their behaviour once the divers retreat. If divers abide by the current code of practice for diving at this site, it is unlikely that their activities will substantially impact Grey Nurse Sharks in the long term.     

Engaging the broader community in biodiversity research: the concept of the COMBER pilot project for divers in ViBRANT

This paper discusses the design and implementation of a citizen science pilot project, COMBER (Citizens' Network for the Observation of Marine BiodivERsity, http://www.comber.hcmr.gr), which has been initiated under the ViBRANT EU e-infrastructure. It is designed and implemented for divers and snorkelers who are interested in participating in marine biodiversity citizen science projects. It shows the necessity of engaging the broader community in the marine biodiversity monitoring and research projects, networks and initiatives. It analyses the stakeholders, the industry and the relevant markets involved in diving activities and their potential to sustain these activities. The principles, including data policy and rewards for the participating divers through their own data, upon which this project is based are thoroughly discussed. The results of the users analysis and lessons learned so far are presented. Future plans include promotion, links with citizen science web developments, data publishing tools, and development of new scientific hypotheses to be tested by the data collected so far.     

Red Coral Fishery at the Costa Brava (NW Mediterranean): Case Study of an Overharvested Precious Coral

Abstract The Mediterranean red coral (Corallium rubrum, L. 1758) is a slow-growing longevous gorgonian that produces a red calcium carbonate skeleton, which is in high demand by the jewellery industry. Its long history of intensive commercial harvesting has resulted in a well-documented decline of its stocks throughout the Mediterranean, becoming especially apparent during the last two decades. Based on the extensive ecological data from the Costa Brava (NE Spain) stocks, this study reviews, for the first time, socioeconomic aspects and the impact of current fishing practices on the red coral population structure and reproductive biology. A comparison of the intensively harvested populations in shallow water with that of the infrequently harvested ones in deep water, along with a population in a marine reserve as well, reveals that 98% of all shallow water colonies show a juvenile size and branching pattern as a result of harvesting. Recent data on the reproductive biology of the species show that 91% of the colonies in shallow water populations (<60 m depth) are not 100% sexually mature. These populations are clearly at the limit of their recoverability potential. The maximum sustainable yield (estimated using the Beverton-Holt model) is reached at an age of first capture of 98 years, although the current regulations allow harvesting of approximately 11-year-old colonies (corresponding to a basal diameter of 7 mm). The presented data reveal how this renewable resource is being exploited in a clearly non-sustainable and inefficient way, changing significantly the underwater landscape of the Mediterranean coast. The review of all available data suggests that the shallow water stocks are depleted. Furthermore, recent trends in poaching of juvenile colonies and mass mortality events threaten the survival of the shallow water populations. A ban on reconstituted coral from the market appears to be the only option to control this form of poaching.     

An evaluation of artificial substrates for sampling macrobenthos in reservoirs

Artificial substrates were compared with a Ponar grab for sampling benthic macroinvertebrates in Lake Anna, Louisa Co., Virginia. The objective was t0 find which technique was best for assessment 0f thermal effluent effects using the following criteria: 1) provide reliable data on density and composition 0f the macrobenthos with a reasonable number 0f replicates; 2) collect the most taxa; and, 3) require the least amount 0f time. Leaves, 3M Corporation's #200 conservation web, and limestone rocks were compared. Each material was tested separately in chicken wire baskets placed 0n the bottom at several depths. Three replicates of each type were retrieved monthly from each depth using SCUBA and cloth flour sacks and compared with grab samples taken from the same depths. Lesser amounts of these materials were tested separately in smaller plastic containers. All large artificial substrate samplers collected significantly more individuals (P = 0.05) and taxa than the Ponar grab. Small web and leaf samplers best met all three 0f the established criteria. The SCUBA system developed in the study is a fast and reliable sampling method.     

Does fluctuating salinity induce branching of Fucus vesiculosus?

During the field surveys in the Bothnian Sea, i.e. towards low salinity areas (approx. 4), present authors observed that the frequency of irregularly branched Fucus vesiculosus plants increased. Salinity is known to decrease gradually towards the northern parts of the Baltic Sea. However, salinity is not steady but may fluctuate greatly on an annual and even a daily scale, and salinity can drop to zero for short periods. In order to demonstrate whether the fluctuating salinity induces irregular branching of F. vesiculosusus, a experiment was carried out in the Tvärminne archipelago, on the south coast of Finland in May–September 1997. First, plants were collected and then put into two containers both of which had a fresh water and a sea water flow throught. After 48 h of treatment, the plants were removed to the same place where they had been orginally collected. After the growing season, the plants were collected again, and the number of irregularly and normally branched tips were measured. The results shows that plants with the fresh water treatment have branched irregularly. In constrast, the control plants had only a few irregularly branched tips. This experiment brings us to conclude that low salinity during the critical growing season induces irregular branching.