Deriving optimal fishing effort for managing Australia's Moreton Bay multispecies trawl fishery with aggregated effort data

Deriving an estimate of optimal fishing effort or even an approximate estimate is very valuable for managing fisheries with multiple target species. The most challenging task associated with this is allocating effort to individual species when only the total effort is recorded. Spatial information on the distribution of each species within a fishery can be used to justify the allocations, but often such information is not available. To determine the long-term overall effort required to achieve maximum sustainable yield (MSY) and maximum economic yield (MEY), we consider three methods for allocating effort: (i) optimal allocation, which optimally allocates effort among target species; (ii) fixed proportions, which chooses proportions based on past catch data; and (iii) economic allocation, which splits effort based on the expected catch value of each species. Determining the overall fishing effort required to achieve these management objectives is a maximizing problem subject to constraints due to economic and social considerations. We illustrated the approaches using a case study of the Moreton Bay Prawn Trawl Fishery in Queensland (Australia). The results were consistent across the three methods. Importantly, our analysis demonstrated the optimal total effort was very sensitive to daily fishing costs—the effort ranged from 9500–11 500 to 6000–7000, 4000 and 2500 boat-days, using daily cost estimates of $0, $500, $750, and $950, respectively. The zero daily cost corresponds to the MSY, while a daily cost of $750 most closely represents the actual present fishing cost. Given the recent debate on which costs should be factored into the analyses for deriving MEY, our findings highlight the importance of including an appropriate cost function for practical management advice. The approaches developed here could be applied to other multispecies fisheries where only aggregated fishing effort data are recorded, as the literature on this type of modelling is sparse.

Effect of water quality and season on the population dynamics of Cabomba caroliniana in subtropical Queensland, Australia

Cabomba caroliniana is a submersed aquatic macrophyte that originates from the Americas and is currently invading temperate, subtropical, and tropical freshwater habitats around the world. Despite being a nuisance in many countries, little is known about its ecology. We monitored C. caroliniana populations in three reservoirs in subtropical Queensland, Australia, over 5.5 years. Although biomass, stem length, and plant density of the C. caroliniana stands fluctuated over time, they did not exhibit clear seasonal patterns. Water depth was the most important environmental factor explaining C. caroliniana abundance. Plant biomass was greatest at depths from 2–4 m and rooted plants were not found beyond 5 m. Plant density was greatest in shallow water and decreased with depth, most likely as a function of decreasing light and increasing physical stress. We tested the effect of a range of water physico-chemical parameters. The concentration of phosphorus in the water column was the variable that explained most of the variation in C. caroliniana population parameters. We found that in subtropical Australia, C. caroliniana abundance does not appear to be affected by seasonal conditions but is influenced by other environmental variables such as water depth and nutrient loading. Therefore, further spread will more likely be governed by local habitat rather than climatic conditions.

Effect of water quality and season on the population dynamics of Cabomba caroliniana in subtropical Queensland, Australia

Cabomba caroliniana is a submersed aquatic macrophyte that originates from the Americas and is currently invading temperate, subtropical, and tropical freshwater habitats around the world. Despite being a nuisance in many countries, little is known about its ecology. We monitored C. caroliniana populations in three reservoirs in subtropical Queensland, Australia, over 5.5 years. Although biomass, stem length, and plant density of the C. caroliniana stands fluctuated over time, they did not exhibit clear seasonal patterns. Water depth was the most important environmental factor explaining C. caroliniana abundance. Plant biomass was greatest at depths from 2–4 m and rooted plants were not found beyond 5 m. Plant density was greatest in shallow water and decreased with depth, most likely as a function of decreasing light and increasing physical stress. We tested the effect of a range of water physico-chemical parameters. The concentration of phosphorus in the water column was the variable that explained most of the variation in C. caroliniana population parameters. We found that in subtropical Australia, C. caroliniana abundance does not appear to be affected by seasonal conditions but is influenced by other environmental variables such as water depth and nutrient loading. Therefore, further spread will more likely be governed by local habitat rather than climatic conditions.

Evaluating the role of extension in helping to improve water quality in the Great Barrier Reef

From 2012-2014 the Queensland Government delivered an extension project to help sugarcane growers adopt best management practices to reduce pollutant loss to the Great Barrier Reef. Coutts J&R were engaged to measure progress towards the project's engagement, capacity gain and practice change targets. The monitoring and evaluation program comprised a database, post-workshop evaluations and grower and advisor surveys. Coutts J&R conducted an independent phone survey with 97 growers, a subset of the 900 growers engaged in extension activities. Of those surveyed 64% stated they had made practice changes. There was higher (74%) adoption by growers engaged in one-on-one extension than those growers only involved in group-based activities (36%). Overall, the project reported 41% (+/-10%, 95% confidence) of growers engaged made a practice change. The structured monitoring and evaluation program, including independent surveys, was essential to quantify practice change and demonstrate the effectiveness of extension in contributing to water quality improvement.

Water quality assessment and characterisation of chlorophyll-a variability related to river discharges, within the southeastern Bay of Biscay : evaluation and development of chlorophyll-a algorithms for MODIS and MERIS imagery

222 p. : il.

Economics of co-managing water quality and invasive species for California and Baja California coastal boats

Regulatory action to protect California’s coastal water quality from degradation by copper from recreational boats’ antifouling paints interacts with efforts to prevent transport of invasive, hull-fouling species. A copper regulatory program is in place for a major yacht basin in northern San Diego Bay and in process for other major, California boat basins. “Companion” fouling control strategies are used with copper-based antifouling paints, as some invasive species have developed resistance to the copper biocide. Such strategies are critical for boats with less toxic or nontoxic hull coatings. Boat traffic along over 3,000 miles of coastline in California and Baja California increases invasive species transport risks. For example, 80% of boats in Baja California marinas are from the United States, especially California. Policy makers, boating businesses and boat owners need information on costs and supply-side capacity for effective fouling control measures to co-manage water quality and invasive species concerns. (PDF contains 3 pages)

Water quality objectives as a management tool for sustainability

The aim of this paper is to explore the potential role that quality objectives, particularly when backed by statutory force, may play in the sustainable management of river water quality. Economic valuation techniques are discussed, as well as the theory of "critical natural capital". A brief history of water quality legislation includes the implementation of the National Water Council classification in 1979, and the statutory water quality objectives introduced under the Water Resources Act 1991.

Worsening water quality conditions at Inner Puno Bay, Lake Titicaca, Peru, and their effect on Lemna spp. biomass

Although there have been a number of studies on aquatic conditions and the flora and fauna of Lake Titicaca over many decades, most of this work has been centred on the offshore regions of the main lake. Water quality there has been degrading and abundant growth of Lemna spp. has been developing. Lemna spp., commonly called floating duck-weed or ‘lenteja de agua’ in Puno, occurs perennially in most parts of the inner Puno Bay shore-line. In this article, the authors compare water quality changes over recent decades in shore-line regions of Inner Puno Bay and their possible effects on the distribution, abundance and biomass of Lemna spp..

A tool for better management of water quality during periods of algal blooms: the case of the River Oise

Like other rivers in the Paris area, the Oise is subject to important seasonal algal blooms. This eutrophication generates notable problems for the production of drinking-water from a treatment plant on the river at Méry. A mathematical model has been developed to simulate variation in water quality in a pre-treatment storage basin, and another model is currently being adapted to model the River Oise. Integration of the two models should provide a comprehensive tool for predicting variations of phytoplankton and water-quality parameters associated with algal blooms. This will be a decision-aid for optimizing control of the treatment process for providing potable water.

Linking elements of the Integrated Ocean Observing System (IOOS) with the planned National Water Quality Monitoring Network. Proceedings from the NOAA-Supported workshop 19-21 September 2005

The National Oceanic and Atmospheric Administration (NOAA), in cooperation with the New Jersey Marine Sciences Consortium (NJMSC), hosted a workshop at Rutgers University on 19-21 September 2005 to explore ways to link the U.S. Integrated Ocean Observing System (IOOS) to the emerging infrastructure of the National Water Quality Monitoring Network (NWQMN). Participating partners included the Mid-Atlantic Coastal Ocean Observing Regional Association, U.S. Geological Survey, Rutgers University Coastal Ocean Observing Laboratory, and the New Jersey Sea Grant College. The workshop was designed to highlight the importance of ecological and human health linkages in the movement of materials, nutrients, organisms and contaminants along the Delaware Bay watershed-estuary-coastal waters gradient (hereinafter, the “Delaware Bay Ecosystem [DBE]”), and to address specific water quality issues in the mid-Atlantic region, especially the area comprising the Delaware River drainage and near-shore waters. Attendees included federal, state and municipal officials, coastal managers, members of academic and research institutions, and industry representatives. The primary goal of the effort was to identify key management issues and related scientific questions that could be addressed by a comprehensive IOOS-NWQMN infrastructure (US Commission on Ocean Policy 2004; U.S. Ocean Action Plan 2004). At a minimum, cooperative efforts among the three federal agencies (NOAA, USGS and EPA) involved in water quality monitoring were required. Further and recommended by the U.S. Commission on Ocean Policy, outreach to states, regional organizations, and tribes was necessary to develop an efficient system of data gathering, quality assurance and quality control protocols, product development, and information dissemination.

Fine sediment resuspension dynamics in Moreton Bay

A comprehensive field study has been undertaken to investigate sediment resuspension dynamics in the Moreton Bay, a large semi-enclosed bay situated in South East Queensland, Australia. An instrumented tripod, which housed three current meters, three OBS sensors and one underwater video camera, was used to collect the field data on tides, currents, waves and suspended sediment concentrations at four sites (Sites 1, 2, 4, and 5) in the bay. Site I was located at the main entrance, Site 2 at the central bay in deep water, and Sites 4 and 5 at two small bays in shallow water. The bed sediment was fine sand (d(50) = 0. 2 mm) at Site 1, and cohesive sediment at the other three sites. Based on the collected field data, it is found that the dominant driving forces for sediment resuspension are a combination of ocean swell and tidal currents at Site 1, tidal currents at Site 2, and wind-waves at Sites 4 and 5. The critical bed shear stress for cohesive sediment resuspension is determined as 0. 079 Pa in unidirectional flow at Site 2, and 0. 076 Pa in wave-induced oscillatory flow at Site 5.