Developing effective restoration plans to tackle the widespread impairment of coastal swimming and shellfishing waters

Congress established a legal imperative to restore the quality of our surface waters when it enacted the Clean Water Act in 1972. The act requires that existing uses of coastal waters such as swimming and shellfishing be protected and restored. Enforcement of this mandate is frequently measured in terms of the ability to swim and harvest shellfish in tidal creeks, rivers, sounds, bays, and ocean beaches. Public-health agencies carry out comprehensive water-quality sampling programs to check for bacteria contamination in coastal areas where swimming and shellfishing occur. Advisories that restrict swimming and shellfishing are issued when sampling indicates that bacteria concentrations exceed federal health standards. These actions place these coastal waters on the U.S. Environmental Protection Agencies’ (EPA) list of impaired waters, an action that triggers a federal mandate to prepare a Total Maximum Daily Load (TMDL) analysis that should result in management plans that will restore degraded waters to their designated uses. When coastal waters become polluted, most people think that improper sewage treatment is to blame. Water-quality studies conducted over the past several decades have shown that improper sewage treatment is a relatively minor source of this impairment. In states like North Carolina, it is estimated that about 80 percent of the pollution flowing into coastal waters is carried there by contaminated surface runoff. Studies show this runoff is the result of significant hydrologic modifications of the natural coastal landscape. There was virtually no surface runoff occurring when the coastal landscape was natural in places such as North Carolina. Most rainfall soaked into the ground, evaporated, or was used by vegetation. Surface runoff is largely an artificial condition that is created when land uses harden and drain the landscape surfaces. Roofs, parking lots, roads, fields, and even yards all result in dramatic changes in the natural hydrology of these coastal lands, and generate huge amounts of runoff that flow over the land’s surface into nearby waterways. (PDF contains 3 pages)

Information collected in Teesdale concerning free-swimming stages of brown trout (Salmo trutta L.)

During 1978 and 1979, electrofishing surveys were made in Teesdale - both to provide background information for ecological work on the streams, and to provide data so that the influence of discharge regime on the fish population densities could be examined. The discharge regimes of the different streams were compared using the Base Flow Index (BFI) as developed by the Institute of Hydrology. (PDF contains 30 pages)

Effects of seasonal change on activity rhythms and swimming behavior of age-0 bluefish (Pomatomus saltatrix) and a description of gliding behavior

Daily and seasonal activity rhythms, swimming speed, and modes of swimming were studied in a school of spring-spawned age-0 bluefish (Pomatomus saltatrix) for nine months in a 121-kL research aquarium. Temperature was lowered from 20° to 15°C, then returned to 20°C to match the seasonal cycle. The fish grew from a mean 198 mm to 320 mm (n= 67). Bluefish swam faster and in a more organized school during day (overall mean 47 cm/s) than at night (31 cm/s). Swimming speed declined in fall as temperature declined and accelerated in spring in response to change in photoperiod. Besides powered swimming, bluefish used a gliding-upswimming mode, which has not been previously described for this species. To glide, a bluefish rolled onto its side, ceased body and tail beating, and coasted diagonally downward. Bluefish glided in all months of the study, usually in the dark, and most intensely in winter. Energy savings while the fish is gliding and upswimming may be as much as 20% of the energy used in powered swimming. Additional savings accrue from increased lift due to the hydrofoil created by the horizontal body orientation and slightly concave shape. Energy-saving swimming would be advantageous during migration and overwintering.

Duration of unassisted swimming activity for spotted dolphin (Stenella attenuata) calves: implications for mother-calf separation during tuna purse-seine sets

Size-related differences in power production and swim speed duration may contribute to the observed deficit of nursing calves in relation to lactating females killed in sets by tuna purse-seiners in the eastern tropical Pacific Ocean (ETP). Power production and swim-speed duration were estimated for northeastern spotted dolphins (Stenella attenuata), the species (neonate through adult) most often captured by the fishery. Power required by neonates to swim unassisted was 3.6 times that required of an adult to swim the same speed. Estimated unassisted burst speed for neonates is only about 3 m/s compared to about 6 m/s for adults. Estimated long-term sustainable speed is about 1 m/s for neonates compared to about 2.5 m/s for adults. Weight-specific power requirements decrease as dolphin calves increase in size, but power estimates for 2-year-old spotted dolphin calves are still about 40% higher than power estimates for adults, to maintain the same speed. These estimated differences between calves and adults are conservative because the calculations do not include accommodation for reduced aerobic capacity in dolphin calves compared to adults. Discrepancies in power production are probably ameliorated under normal circumstances by calves drafting next to their mothers, and by employing burst-coast or leap-burst-coast swimming, but the relatively high speeds associated with evasion behaviors during and after tuna sets likely diminish use of these energy-saving strategies by calves.

Swimming crab Callinectes amnicola (Decapoda-Portunidae) capture analysis of a lagoon with high continental influence (Aby Lagoon, Cote d'Ivoire, West Africa)

The study describes the main causes of captures and productions decreasing of swimming crab Callinectes amnicola (Decapoda Portunidae) in Aby lagoon complex. For that, docks of two Sub Prefectures of Adiaké and Assini-Mafia respectively including the villages of Adiaké, Anga, Assomlan, Epleman, Aby and Man-Man, M'Bratty, Assini-Ngouankro and Assini-Mafia were studied from 2006 to 2009 and completed with previous results obtained from 1988 to 2005. Field investigators were identified by site/village and they recorded daily activities of fishermen (number of effective fishermen, number of gears and area of fishing, duration of fishing, types and quantity of bait) and landing of swimming crabs. During recent period of the study, total production decreased from 3742 tons in 2006 to 1500 tons in 2009. Matrix correlations and correlation analysis indicated that this downward trend was due to the increase of the number of fishermen, number of fishing gear, the decrease in female crabs capture and degradation of the environment related to gradual closure of the Assini-Mafia channel. Despite this decline, total production in Aby lagoon remained high compared to the productions of some lagoons of the country and the region. Given the importance of fishing swimming crabs in Aby lagoon, since it concerns many young people and it is a source of income, stringent measures for sustainable and responsible management must be taken and implemented as part of a co-management plan involving all stakeholders to sustainably manage the resource

Swimming depth, ambient water temperature preference, and feeding frequency of young Pacific bluefin tuna (Thunnus orientalis) determined with archival tags

We investigated the migration and behavior of young Pacific Bluefin tuna (Thunnus orientalis) using archival tags. The archival tag measures environmental variables, records them in its memory, and estimates daily geographical locations based on measured light levels. Of 166 archival tags implanted in Pacific bluefin tuna that were released at the northeastern end of the East China Sea from 1995 to 1997, 30 tags were recovered, including one from a fish that migrated across the Pacific. This article describes swimming depth, ambient water temperature, and feeding frequency of young Pacific bluefin tuna based on retrieved data. Tag performance, effect of the tag on the fish, and horizontal movements of the species are described in another paper. Young Pacific bluefin tuna swim mainly in the mixed layer, usually near the sea surface, and swim in deeper water in daytime than at nighttime. They also exhibit a pattern of depth changes, corresponding to sunrise and sunset, apparently to avoid a specific low light level. The archival tags recorded temperature changes in viscera that appear to be caused by feeding, and those changes indicate that young Pacific bluefin tuna commonly feed at dawn and in the daytime, but rarely at dusk or at night. Water temperature restricts their distribution, as indicated by changes in their vertical distribution with the seasonal change in depth of the thermocline and by the fact that their horizontal distribution is in most cases confined to water in the temperature range of 14−20°C.

Local distribution and abundance of swimming crabs (Callinectes spp. and Arenaeus cribrarius) on a tropical arid beach

Distribution, abundance, and several population features were studied in Ensenada de La Vela (Venezuela) between 1993 and 1998 as a first step in the assessment of local fisheries of swimming crabs. Arenaeus cribrarius was the most abundant species at the marine foreshore. Callinectes danae prevailed at the estuarine location. Callinectes bocourti was the most abundant species at the offshore. Abundances of A. cribrarius and C. danae fluctuated widely and randomly. Ovigerous females were almost absent. Adults of several species were smaller than previously reported. This study suggests that fisheries based on these swimming crabs probably will be restricted to an artisanal level because abundances appear too low to support industrial exploitation.

Crabbing into an uncertain future: the blue swimming crab fisher in coastal town of Eastern Philippines

This research project sought to find out the socio-economic status of the small-scale fishers of the blue swimming crab (Portunuspelagicus) in Samar, considering the diminishing volume of catch of the species in the recent years. Using a blend of quantitative and qualitative methods, the study employed an interview schedule, focus group discussion (FGD) and observation in collecting data not only from the fishers but also from other sectors directly involved in the blue swimming crab industry.

Influence of seagrass landscape structure on the juvenile blue crab habitat-survival function

Organismal survival in marine habitats is often positively correlated with habitat structural complexity at local (within-patch) spatial scales. Far less is known, however, about how marine habitat structure at the landscape scale influences predation and other ecological processes, and in particular, how these processes are dictated by the interactive effect of habitat structure at local and landscape scales. The relationship between survival and habitat structure can be modeled with the habitat-survival function (HSF), which often takes on linear, hyperbolic, or sigmoid forms. We used tethering experiments to determine how seagrass landscape structure influenced the HSF for juvenile blue crabs Callinectes sapidus Rathbun in Back Sound, North Carolina, USA. Crabs were tethered in artificial seagrass plots of 7 different shoot densities embedded within small (1 – 3 m2) or large (>100 m2) seagrass patches (October 1999), and within 10 × 10 m landscapes containing patchy (<50% cover) or continuous (>90% cover) seagrass (July 2000). Overall, crab survival was higher in small than in large patches, and was higher in patchy than in continuous seagrass. The HSF was hyperbolic in large patches and in continuous seagrass, indicating that at low levels of habitat structure, relatively small increases in structure resulted in substantial increases in juvenile blue crab survival. However, the HSF was linear in small seagrass patches in 1999 and was parabolic in patchy seagrass in 2000. A sigmoid HSF, in which a threshold level of seagrass structure is required for crab survival, was never observed. Patchy seagrass landscapes are valuable refuges for juvenile blue crabs, and the effects of seagrass structural complexity on crab survival can only be fully understood when habitat structure at larger scales is considered.

Detecting fish aggregations from reef habitats mapped with high resolution side scan sonar imagery

As part of a multibeam and side scan sonar (SSS) benthic survey of the Marine Conservation District (MCD) south of St. Thomas, USVI and the seasonal closed areas in St. Croix—Lang Bank (LB) for red hind (Epinephelus guttatus) and the Mutton Snapper (MS) (Lutjanus analis) area—we extracted signals from water column targets that represent individual and aggregated fish over various benthic habitats encountered in the SSS imagery. The survey covered a total of 18 km2 throughout the federal jurisdiction fishery management areas. The complementary set of 28 habitat classification digital maps covered a total of 5,462.3 ha; MCDW (West) accounted for 45% of that area, and MCDE (East) 26%, LB 17%, and MS the remaining 13%. With the exception of MS, corals and gorgonians on consolidated habitats were significantly more abundant than submerged aquatic vegetation (SAV) on unconsolidated sediments or unconsolidated sediments. Continuous coral habitat was the most abundant consolidated habitat for both MCDW and MCDE (41% and 43% respectively). Consolidated habitats in LB and MS predominantly consisted of gorgonian plain habitat with 95% and 83% respectively. Coral limestone habitat was more abundant than coral patch habitat; it was found near the shelf break in MS, MCDW, and MCDE. Coral limestone and coral patch habitats only covered LB minimally. The high spatial resolution (0.15 m) of the acquired imagery allowed the detection of differing fish aggregation (FA) types. The largest FA densities were located at MCDW and MCDE over coral communities that occupy up to 70% of the bottom cover. Counts of unidentified swimming objects (USOs), likely representing individual fish, were similar among locations and occurred primarily over sand and shelf edge areas. Fish aggregation school sizes were significantly smaller at MS than the other three locations (MCDW, MCDE, and LB). This study shows the advantages of utilizing SSS in determining fish distributions and density.

Analysis of fish diversion efficiency and survivorship in the fish return system at San Onofre Nuclear Generating Station

This study examined the efficiency of fish diversion and survivorship of diverted fishes in the San Onofre Nuclear Generating Station Fish Return System in 1984 and 1985. Generally, fishes were diverted back to the ocean with high frequency, particularly in 1984. Most species were diverted at rates of 80% or more. Over 90% of the most abundant species, Engraulis mordax, were diverted. The system worked particularly well for strong-swimming forms such as Paralobrax clothratus, Atherinopsis californiensis, and Xenistius californiensis, and did not appreciably divert weaker-swimming species such as Porichthys notatus, Heterostichus rostratus, and Syngnathus sp. Return rates of some species were not as high in 1985 as in 1984. Individuals of most tested species survived both transit through the fish return system and 96 hours in a holding net. Some species, such as E. mordox, X. californiensis, and Umbrina roncador, experienced tittle or no mortality. Survivorship of Seriphus politus was highly variable and no Anchoa delicatissima survived. (PDF file contains 22 pages.)

An egg production method for estimating spawning biomass of pelagic fish: Application to the northern anchovy, Engraulis mordax

Fishery scientists engaged in estimating the size of free-swimming populations have never had a technique available to them whereby all the parameters could be estimated from a resource survey and where no parameter values need to be assumed. Recognizing the need for a technique of this kind, the staff of the Coastal Fisheries Resources Division of the Southwest Fisheries Center (SWFC) devised an egg production method for anchovy biomass assessment. Previously, anchovy biomass was estimated by approximate methods derived from a long-time series and anchovy larval abundance, which required about 5 ma of shiptime each year to integrate the area under a seasonal spawning curve. One major assumption used in the larval abundance census method is that there is constant proportionality between larval numbers and spawning biomass. This has now proved to be erroneous. (PDF file contains 105 pages.)

Horizontale Trennblätter in Trawls zur Verringerung von Discards in der Ostsee

A primary objective of the Common Fishery Policy of the European Union is the reduction of discards and unwanted by-catches in the fishery. In principle this could be achieved if the catching methods were optimised for this. Still high numbers of undersized flatfish are caught in the bottom trawls. Although EU regulations make the use of the BACOMA codend mandatory in the Baltic Sea cod areable to escape through square mesh escape window of the BACOMA net the whereas flatfish still remain in the cod-end. Gear experiments have been carried out with the aim to better separate cod from the flatfish fraction already when entering the rear belly, making use of the natural behaviour of the fish, i. e. the preferred swimming distance from the bottom of the net in the funnel. As cod have a natural tendency to keep a relativly great distance from the bottom, flatfish tend to stay close to it. It was attempted to separate both fractions by splitting the funnel into an upper and lower part with a horizontal panel. This wastested for two different nets, a cod trawl to separate cod from flatfish, and an eel-trawl to separate cod and flatfish from eel. Cod and flatfish separation is best at a panel distance of 50 cm from the bottom. Thus, 74 % of the cod were found in the upper panel, whereas 75 % of the flounder were in the lower section. A separation of eel from cod was however not possible, since eel tend to rise to the upper part of the net, together with cod.

Acute toxicities of Basudine and Gammalin 20 to Aphyosemin gairdneri

Effects of Basudine and Gammalin 20 on the fingerlings of Aphyosemin gairdneri were investigated using static bioassays and continuous aeration over a period of 48 hours. The 48 hours LC sub(50) of the exposed fish to Basudine and Gammalin 20 were determined to be 194.99 mu g dm super(3) and 95.50 mu g dm super(3) respectively. Gammalin 20 was more toxic than Basudine. The behavioural responses observed include agitation, erratic swimming, loss of equilibrium, period of quiescence and death. It is concluded that repeated applications of these herbicides should be avoided before stocking ponds with fish

Acute toxicity of Gammalin 20 to Chrysichthys nigrodigitatus (Lacepede)

The impact of acute exposure of Gammalin 20 (an organochlorine pesticide) was investigated in a static bioassay test over a 96-(4-day) period on the fingerlings of Chrysichthys nigrodigitatus (lacepede). The 96-hLC sub(50) of Gammalin 20 was determined as 2.31 Ug/l with lower and upper limits of toxicities as 2.10 and 4.44 Ug/l respectively. At higher concentrations, the colour of the exposed fish became darker, opercular movement slowed down while pigmentation pattern increased and respiratory distress was observed, erratic swimming, tonic convulsion and no response to gentle prodding, and finally death. The implications of these results were discussed with a suggestion of the total ban on the use of Gammalin 20 in capture fisheries due to its harmful and persistence nature in the aquatic environment