The control of indirect effects of biomanipulation

Results from long-term investigations on biomanipulation show that indirect effects are at least as important as direct effects are for the stability of biomanipulation. Three types of indirect effects can be distinguished: (1) a change in quantity or quality of the resource base, (2) behavioural change of the prey, and (3) development of anti-predator traits. Although indirect effects of type (2), (e.g. a change in the pattern of vertical migration of zooplankton), and type (3), (e.g. development of helmets and neck teeth in Daphnia), are important mechanisms, the most essential indirect effects regarding biomanipulation belong to type (1). An example of the latter will be demonstrated: the complex of indirect effects of enhanced grazing by large herbivores on the phosphorus metabolism of the lake. It is concluded that control of the indirect effects is absolutely necessary to stabilize biomanipulation measures, but this is much more difficult than the control of direct effects and needs deeper insights into the structuring mechanisms of food webs. Proper management of fish stocks, in combination with the control of phosphorus load and/or the physical conditions, seems to be the most promising way of controlling the indirect effects of biomanipulation.

Simple broodstock management to control indirect selection and inbreeding: Indian carp example

Following a survey of the important traits of Indian carp broodstock at some southern Indian hatcheries, it was found that the broodstock selection was size selective, exerting strong, negative selection of prematuration growth rate and positive selection on age at first maturation. This meant that the hatchery bred inadvertently slower growing and later maturing individuals. Details are given of approaches to avoid such negative selection and minimize inbreeding.

Indirect validation of the age-reading method for Pacific cod (Gadus macrocephalus) using otoliths from marked and recaptured fish

Two examples of indirect validation are described for age-reading methods of Pacific cod (Gadus macrocephalus). Aging criteria that exclude faint translucent zones (checks) in counts of annuli and criteria that include faint zones were both tested. Otoliths from marked and recaptured fish were used to back-calculate the length of each fish at the time of its release by using measurements of the area of annuli. Estimated fish size at time of release and actual observed fish size were similar, supporting the assumption that translucent zones are laid down on an annual basis. A second method for validating reading criteria used otolith age and von Bertalanffy parameters, estimated from the tagging data, to predict how much each fish grew in length after tagging. We found that otolith aging criteria applied to otoliths from tagged and recovered Pacific cod predicted quite accurately the growth increments that we observed in these specimens. These results provide further evidence that the current aging criteria are not underestimating the age of the fish and support our current interpretation of checks (i.e., as subannual marks). We expect these indirect validations to advance age determination for Pacific cod, which in turn would enhance development of stock assessment methods based on age structure for this species in the eastern Bering Sea.

Indirect estimates of natural mortality rate for arrowtooth flounder (Atheresthes stomias) and darkblotched rockfish (Sebastes crameri)

Indirect estimates of instantaneous natural mortality rate (M) are widely used in stock assessment and fisheries management. They are essentially a form of meta-analysis, in which prior information on M and key life history parameters from a variety of stocks is used to estimate M for the stock in question.

Strategic planning for long-term financing of Pacific leatherback conservation and recovery:Proceedings of the Bellagio Sea Turtle Conservation Initiative, Terengganu, Malaysia; July 2007

On 17-20 July 2007, 45 experts on sea turtles, fisheries, conservation and finance from 10 countries convened at the Bellagio Sea Turtle Conservation Initiative workshop in Terengganu to focus on methods to save the imperiled Pacific leatherback from extinction. The group developed a strategic plan to guide the prioritization and long term financing of Pacific leatherback turtle conservation and recovery objectives. Participants identified critical conservation actions and agreed that a business plan is urgently needed to reverse the trajectory towards extinction of the Pacific leatherback. The conservation actions prioritized by the participants encompassed protecting nesting beaches including eggs and nesting females; reducing direct and indirect turtle take in coastal fisheries; and strengthening regional and sub-regional cooperation. The group committed to work together on fundraising and implementation of these urgent conservation actions. This report presents outputs and the plan that was produced from the workshop.

Compatibility of Glyphosate with Galerucella calmariensis; a Biological Control Agent for Purple Loosestrife (Lythrum salicaria)

By integrating Galerucella calmariensis with glyphosate there is potential to achieve both immediate and sustained control of purple loosestrife (Lythrum salicaria). The objective of this study was to determine the compatibility of glyphosate on the oviposition and survival of adult G. Calmariensis and on the ability of G. calmariensis third instar larvae to pupate to teneral adults. Our results revealed glyphosate (formulated as Roundup) at a concentration of 2% (2.43L/acre) and 4% solution (4.86 L/acre) had no impact on the ability of G. calmariensis third instar larvae to pupate to new generation adults. To examine the effect of a 2% solution of glyphosate on adult G. calmariensis oviposition and survival, adults were randomly divided between a direct contact group (adults sprayed directly), an indirect contact group (host plants with adults were sprayed), and a control group. Our results revealed that glyphosate does not impact G. calmariensis oviposition or adult survival. The results of this study indicate that G. calmariensis is compatible with glyphosate indicating that further field studies examining integrated control strategies for purple loosestrife are warranted.

Coral Remote Sensing Workshop: Proceedings and Recommendations, 17-18 September, Sheraton, Brickell Ave, Miami FL

Coral reefs exist in warm, clear, and relatively shallow marine waters worldwide. These complex assemblages of marine organisms are unique, in that they support highly diverse, luxuriant, and essentially self-sustaining ecosystems in otherwise nutrient-poor and unproductive waters. Coral reefs are highly valued for their great beauty and for their contribution to marine productivity. Coral reefs are favorite destinations for recreational diving and snorkeling, as well as commercial and recreational fishing activities. The Florida Keys reef tract draws an estimated 2 million tourists each year, contributing nearly $800 million to the economy. However, these reef systems represent a very delicate ecological balance, and can be easily damaged and degraded by direct or indirect human contact. Indirect impacts from human activity occurs in a number of different forms, including runoff of sediments, nutrients, and other pollutants associated with forest harvesting, agricultural practices, urbanization, coastal construction, and industrial activities. Direct impacts occur through overfishing and other destructive fishing practices, mining of corals, and overuse of many reef areas, including damage from souvenir collection, boat anchoring, and diver contact. In order to protect and manage coral reefs within U.S. territorial waters, the National Oceanic and Atmospheric Administration (NOAA) of the U.S. Department of Commerce has been directed to establish and maintain a system of national marine sanctuaries and reserves, and to monitor the condition of corals and other marine organisms within these areas. To help carry out this mandate the NOAA Coastal Services Center convened a workshop in September, 1996, to identify current and emerging sensor technologies, including satellite, airborne, and underwater systems with potential application for detecting and monitoring corals. For reef systems occurring within depths of 10 meters or less (Figure 1), mapping location and monitoring the condition of corals can be accomplished through use of aerial photography combined with diver surveys. However, corals can exist in depths greater than 90 meters (Figure 2), well below the limits of traditional optical imaging systems such as aerial or surface photography or videography. Although specialized scuba systems can allow diving to these depths, the thousands of square kilometers included within these management areas make diver surveys for deeper coral monitoring impractical. For these reasons, NOAA is investigating satellite and airborne sensor systems, as well as technologies which can facilitate the location, mapping, and monitoring of corals in deeper waters. The following systems were discussed as having potential application for detecting, mapping, and assessing the condition of corals. However, no single system is capable of accomplishing all three of these objectives under all depths and conditions within which corals exist. Systems were evaluated for their capabilities, including advantages and disadvantages, relative to their ability to detect and discriminate corals under a variety of conditions. (PDF contains 55 pages)

Multi-species and multi-interest management: An ecosystem approach to market squid (Loligo opalescens) harvest in California

Market squid (Loligo opalescens) plays a vital role in the California ecosystem and serves as a major link in the food chain as both a predator and prey species. For over a century, market squid has also been harvested off the California coast from Monterey to San Pedro. Expanding global markets, coupled with a decline in squid product from other parts of the world, in recent years has fueled rapid expansion of the virtually unregulated California fishery. Lack of regulatory management, in combination with dramatic increases in fishing effort and landings, has raised numerous concerns from the scientific, fishing, and regulatory communities. In an effort to address these concerns, the National Oceanic and Atmospheric Administration’s (NOAA) Channel Islands National Marine Sanctuary (CINMS) hosted a panel discussion at the October 1997 California Cooperative Oceanic and Fisheries Investigations (CalCOFI) Conference; it focused on ecosystem management implications for the burgeoning market squid fishery. Both panel and audience members addressed issues such as: the direct and indirect effects of commercial harvesting upon squid biomass; the effects of harvest and the role of squid in the broader marine community; the effects of environmental variation on squid population dynamics; the sustainability of the fishery from the point of view of both scientists and the fishers themselves; and the conservation management options for what is currently an open access and unregulated fishery. Herein are the key points of the ecosystem management panel discussion in the form of a preface, an executive summary, and transcript. (PDF contains 33 pages.)

The economic importance of marine angler expenditures in the United States.

In 1998, the National Marine Fisheries Service (NMFS) began a series of marine angler expenditure surveys in the coastal regions of the United States (U.S.) to evaluate marine recreational fishing expenditures and the financial impacts of these expenditures in each region and the U.S. as a whole. In this report, we use the previously estimated expenditure estimates to assess the total financial impact of anglers’ saltwater expenditures. Estimates are provided for sales, income, employment, and tax impacts for each coastal state in the U.S. Aggregate estimates are also provided for the entire U.S., excluding Alaska, Hawaii, and Texas. Direct, indirect, and induced effects associated with resident and non-resident angler expenditures were estimated using a regional input-output modeling system called IMPLAN Pro. Nationwide, recreational saltwater fishing generated over $30.5 billion in sales in 2000, nearly $12.0 billion in income, and supported nearly 350,000 jobs. Approximately 89 cents of every dollar spent by saltwater anglers was estimated to remain within the U.S. economy. At the state level, many of the goods anglers purchased were imports, and, as such, as little as 44 cents of every dollar stayed in Rhode Island and as much as 80 cents of every dollar stayed in Georgia. In the Northeast, the highest impacts were generated in New Jersey, even though recreational fishing expenditures in Massachusetts and Maryland were considerably higher. In the Southeast, the highest impacts were generated in Florida, and on the Pacific Coast, the highest impacts were generated in California. Expenditures on boat maintenance/expenses generated more impacts than any other expenditure category in the U.S. Expenditures on rods and reels was the single most important expense category in terms of generating impacts in most of the Northeast states. Expenditures on boat expenses generated the highest in most Southeast states, and expenditures for boat accessories produced the highest impacts in most Pacific Coast states.(PDF file contains 184 pages.)

Effects of underwater explosions on oysters, crabs and fish: a preliminary report.

Investigation on the effects of explosive shock on marine life. Necessary that the "commercial" effects, the actual damage to commercially important stocks of fish and shellfish, be evaluated. Equally important are the "biological" effects, the immediate physical effects of shock waves on animals and the indirect effects on future stocks. Indirect effects might include the diversion of migratory stocks from an area, or actual damage to the habitat, rendering it unfit for sedentary or non-migratory native species. Interruption of the food chains in an area by destruction of forge forms or vegetation. (PDF contains 43 pages)

A proposed integrated livestock-rice-poultry-cum-fish culture in enclosure system

Integrated agriculture-cum-fish farming has been practised profitably for ages in the Chinese small-scale farming system. There is a great potential for this system by utilizing the vast Nigerian flood plains (approx. 515,000 ha). Dogongari Bay in Lake Kainji Basin was identified as a suitable site for this system after some extensive fish culture trials. Polyculture of Clarias spp., Heterotis niloticus and Tilapia was proposed for integration with layers in the poultry house, 2-ha upland rain-fed rice farming and indirect cattle rearing in the 5-ha enclosure site. Cost benefit analysis showed that the system will consistently record profit as from the second year of operation. Various complex factors were identified to affect profitability of this mixed farming system. Concerted research approach is needed to fully understand the interrelationships of the various components of this integrated system. Generous funding of research activities is very crucial in this situation

Environmental hazards to small scale fisheries resources management in Nigeria

This paper examined the environmental hazards limiting sustainable small-scale fisheries development in Nigeria. Observation has showed that hazards range from pollution of the aquatic habitats by domestic and urban sewage and garbage, agro-chemicals, industrial pollutants, crude oil spillage etc. In an attempt to maximize catch, many migrant and part-time fisher folks indulge in highly destructive and obnoxious fishing practices with adverse impact on fisheries resources. These have constituted significant environmental hazards. Discharges of waste from aquacultural practices in to rivers and lakes have also been identified as sources of environmental hazards. Some aquatic weeds such as water hyacinth are sources of hazards. The effects of environmental hazards on small-scale fisheries resources may be direct arising from the toxicity of pollutants or indirect as a result of ecosystem modification. Some of the effects of pollutants on the aquatic environment and fish have been discussed in the paper

The influence of global warming on freshwater plankton communities in Britain

The likely response of freshwater plankton to the direct and indirect effects of sustained global warming are summarized. The increase in CO2 posited by climatologists will have a direct effect on many biological processes, and an even more important indirect effect on the global climate. Lake plankton populations are relatively well buffered against sudden fluctuations in temperature but can react in unexpected ways to seasonal changes in the wind speed, with effects on seasonal growth and succession of plankton. The direct

Herpetofaunal Inventories of the National Parks of South Florida and the Caribbean: Volume II. Virgin Islands National Park

Amphibian declines and extinctions have been documented around the world, often in protected natural areas. Concern for this alarming trend has focused attention on the need to document all species of amphibians that occur within U.S. National Parks and to search for any signs that amphibians may be declining. This study, an inventory of amphibian species in Virgin Islands National Park, was conducted from 2001 to 2003. The goals of the project were to create a georeferenced inventory of amphibian species, use new analytical techniques to estimate proportion of sites occupied by each species, look for any signs of amphibian decline (missing species, disease, die-offs, etc.), and to establish a protocol that could be used for future monitoring efforts. Several sampling methods were used to accomplish these goals. Visual encounter surveys and anuran vocalization surveys were conducted in all habitats throughout the park to estimate the proportion of sites or proportion of area occupied (PAO) by amphibian species in each habitat. Line transect methods were used to estimate density of some amphibian species and double observer analysis was used to refine counts based on detection probabilities. Opportunistic collections were used to augment the visual encounter methods for rare species. Data were collected during four sampling periods and every major trail system throughout the park was surveyed. All of the amphibian species believed to occur on St. John were detected during these surveys. One species not previously reported, the Cuban treefrog (Osteopilus septentrionalis), was also added to the species list. That species and two others (Eleutherodactylus coqui and Eleutherodactylus lentus) bring the total number of introduced amphibians on St. John to three. We detected most of the reptile species thought to occur on St. John, but our methods were less suitable for reptiles compared to amphibians. No amphibian species appear to be in decline at this time. We found no evidence of disease or of malformations. Our surveys provide a snapshot picture of the status of the amphibian species, so continued monitoring would be necessary to determine long-term trends, but several potential threats to amphibians were identified. Invasive species, especially the Cuban treefrog, have the potential to decrease populations of native amphibians. Introduced mammalian predators are also a potential threat, especially to the reptiles of St. John, and mammalian grazers might have indirect effects on amphibians and reptiles through habitat modification. Finally, loss of habitat to development outside the park boundary could harm some important populations of amphibians and reptiles on the island.