Prioritizing seagrass restoration sites: study examines predictors of seagrass bed recovery

Ecologic researchers are modeling the impact of vessel grounding to seagrass beds using GIS in the Florida Keys National Marine Sanctuary. The surface creation tools in the ArcGIS 3D Analyst extension help assess both the damage and recovery of these seagrass beds.

Coupling ecology and economy: modeling optimal release scenarios for summer flounder (Paralichthys dentatus) stock enhancement

Increasing interest in the use of stock enhancement as a management tool necessitates a better understanding of the relative costs and benefits of alternative release strategies. We present a relatively simple model coupling ecology and economic costs to make inferences about optimal release scenarios for summer flounder (Paralichthys dentatus), a subject of stock enhancement interest in North Carolina. The model, parameterized from mark-recapture experiments, predicts optimal release scenarios from both survival and economic standpoints for varyious dates-of-release, sizes-at-release, and numbers of fish released. Although most stock enhancement efforts involve the release of relatively small fish, the model suggests that optimal results (maximum survival and minimum costs) will be obtained when relatively large fish (75–80 mm total length) are released early in the nursery season (April). We investigated the sensitivity of model predictions to violations of the assumption of density-independent mortality by including density-mortality relationships based on weak and strong type-2 and type-3 predator functional responses (resulting in depensatory mortality at elevated densities). Depending on postrelease density, density-mortality relationships included in the model considerably affect predicted postrelease survival and economic costs associated with enhancement efforts, but do not alter the release scenario (i.e. combination of release variables) that produces optimal results. Predicted (from model output) declines in flounder over time most closely match declines observed in replicate field sites when mortality in the model is density-independent or governed by a weak type-3 functional response. The model provides an example of a relatively easy-to-develop predictive tool with which to make inferences about the ecological and economic potential of stock enhancement of summer flounder and provides a template for model creation for additional species that are subjects of stock enhancement interest, but for which limited empirical data exist.

Estimating the emigration rate of fish stocks from marine sanctuaries using tag-recovery data

A critical process in assessing the impact of marine sanctuaries on fish stocks is the movement of fish out into surrounding fished areas. A method is presented for estimating the yearly rate of emigration of animals from a protected (“no-take”) zone. Movement rates for exploited populations are usually inferred from tag-recovery studies, where tagged individuals are released into the sea at known locations and their location of recapture is reported by fishermen. There are three drawbacks, however, with this method of estimating movement rates: 1) if animals are tagged and released into both protected and fished areas, movement rates will be overestimated if the prohibition on recapturing tagged fish later from within the protected area is not made explicit; 2) the times of recapture are random; and 3) an unknown proportion of tagged animals are recaptured but not reported back to researchers. An estimation method is proposed which addresses these three drawbacks of tag-recovery data. An analytic formula and an associated double-hypergeometric likelihood method were derived. These two estimators of emigration rate were applied to tag recoveries from southern rock lobsters (Jasus edwardsii) released into a sanctuary and into its surrounding fished area in South Australia.

Recovery of the Gulf of Maine--Georges Bank Atlantic herring (Clupea harengus) complex: perspectives based on bottom trawl survey data

NMFS bottom trawl survey data were used to describe changes in distribution, abundance, and rates of population change occurring in the Gulf of Maine–Georges Bank herring (Clupea harengus) complex during 1963–98. Herring in the region have fully recovered following severe overfishing during the 1960s and 1970s. Three distinct, but seasonally intermingling components from the Gulf of Maine, Nantucket Shoals (Great South Channel area), and Georges Bank appear to compose the herring resource in the region. Distribution ranges contracted as herring biomass declined in the late 1970s and then the range expanded in the 1990s as herring increased. Analysis of research survey data suggest that herring are currently at high levels of abundance and biomass. All three components of the stock complex, including the Georges Bank component, have recovered to pre-1960s abundance. Survey data support the theory that herring recolonized the Georges Bank region in stages from adjacent components during the late 1980s, most likely from herring spawning in the Gulf of Maine.

Fijian coral reef damage and recovery from Cyclone Kina

EXTRACT (SEE PDF FOR FULL ABSTRACT): Early in 1993, Cyclone Kina struck the Fiji Islands, causing more than $100 million in property damage and damaging the coral environment as well. A few days after the cyclone, the most damaged reef was studied. The same reef had been studied 6 months before. This reef crest is dominated by Acropora. Comparison showed that 80-90% of the Acropora was torn from the outer reef and deposited in the inner lagoon. ... It is estimated that it will take a few years to 30 years for the reef to recover to pre-Kina conditions.

Recovery of a leucosid crab Nursia abbreviata Bell, 1855 from Arabian Sea fish

On two occasions Nursia abbreviata Bell, 1855 has been recovered from the stomachs of Batrochus grunniens (Linnaeus, 1758) caught with commercial fish. Nursia abbreviata has been previously recorded from Karachi by Alcock (1896). The present specimens afford the first subsequent record of the species from the region, and are represented by only two males recovered from fish stomachs. The only other species of the genus from Pakistan is N. Rubifera Muller, 1866 which is common in shore collections (Tirmizi and Kazmi, 1988). A brief description of the present material is given below.

Mussel recovery and species dynamics at four California rocky intertidal sites: 1992 data report

This is an interim report for a study of mussel recovery and species dynamics at four California rocky intertidal sites. Conducted by Kinnetic Laboratories, Inc. (KLI), and funded by the Minerals Management Service (MMS), the initial experimental field study began in spring 1985 and continued through spring 1991. The initial field study included six sites along the central and northern California coast. In 1992, MMS decided to continue the work started by KLI through an in-house study and establishment of the MMS Intertidal (MINT) team. Four of the original six sites have been continued by MMS. The study methods of the original study have been retained by the MINT team, and close coordination with the original KLI team continues. In 1994, the MMS Environmental Studies Program officially awarded a contract to the MINT team for this in-house study. This interim report presents the results from the fall 1992 sampling, the first year of sampling by the MINT team. The report presents a limited statistical analysis and visual comparison of the 1992 data. The next interim report will include data collected during fall 1994 and will present a broader statistical analysis of both the 1992 and 1994 data sets.

Growth performance, recovery rate and fish yield of GIFT strain at various water depths under rice-fish culture systems

Effect of water depth on recovery rate, growth performance and fish yield of GIFT in the rice-fish production systems was studies in experimental plots of 123 m2 with a pond refuge of I meter deep which covered 10% of the total land area. Mortality rate of fish was very low ranging from 0.81-1.63%. However, at harvest, recovery rate ranged from 76.69-82.93% with the highest recovery at 11-15 em of water depth. Significantly the highest absolute growth (99.97) and specific growth rate (2.42%) were found at 21-25 cm water depth. The same treatment also produced significantly higher fish yield (909.76 kg/ha) although statistically similar to the fish yield (862.60 kg/ha) obtained at ll-15 em of water depth. Results also suggested that higher water depth can produce bigger fish but no significant effects of water depth was found on fish yield in the treatments 11-15 cm and 21-25 cm water depths of this experiment.