Movement of yellowtail snapper (Ocyurus chrysurus Block 1790) and black grouper (Mycteroperca bonaci Poey 1860) in the northern Florida Keys National Marine Sanctuary as determined by acoustic telemetry

We tagged a total of 14 yellowtail snapper (Ocyurus chrysurus Bloch 1790) and black grouper (Mycteroperca bonaci Poey 1860) inside the Conch Reef Research Only Area (a no-take marine reserve) in the northern Florida Keys National Marine Sanctuary in November 2001. Both species are heavily exploited in the region. Our objective was to characterize site fidelity and movement behavior along the reef tract to the north and south of the release point. Fishes were collected by baited hook and line from the surface, surgically-tagged with coded-acoustic transmitters, and returned to the reef by snorkelers. Tracking of fish movement behavior was conducted by five acoustic receivers deployed on the seafloor from Davis Reef in the south to Pickles Reef in the north. Fishes were tracked for up to eight months. Results indicated that the majority of signal detections for individual fish from both species were recorded at the two Conch Reef receivers. Limited movement from Conch Reef to Davis Reef was recorded, but no signal detections were recorded at the two sites to the north of Conch Reef. These results suggest that both species show site fidelity to Conch Reef. Future studies will seek to characterize this site fidelity with increased temporal and spatial resolution at Conch Reef. (PDF contains 25 pages.)

Marketing of value-added products from silver carp and involvement of rural people in the production and marketing chain

Cost-profit analysis and market testing of some value-added products from silver carp such as fish mince block, fish sausage, fish ball, fish stick and fish burger were analyzed during April 2001 to March 2002. The study also explored the possibility to involve rural low-income people in the production and marketing of such products. The production of silver carp was higher in greater Jessore and Mymensingh districts but the price remained low during the peak-harvesting season in October to November. The price varied with size of the fish, season, market characteristics and effective demand of the buyers. Price of about 500 g size fish was found to be Tk. 20-25/kg in the rural markets. The average size of fish in the rural markets was 3S0-550 g while that in the urban markets it was 700-1,200 g. The cost of production of the value added products and profit margin were assessed on the basis of market price of the raw material as well as that of the finished products, transportation, storage and marketing costs. The profit margins of 34%, 39%, 81% and 31% of their sales price were obtained for fish sausage, fish ball, fish stick and fish burger, respectively. Actual production cost could be minimized if the fish is purchased directly from the farmers. Consumer's acceptance and marketability tests showed that both rural and urban people preferred fish ball than fish sausage. However, response towards the taste, flavor and color of fish ball and fish sausage was found to vary with occupations and age of the consumers. A correlation was observed between age group and acceptance of new products. Fish ball, fish stick and fish burger were found to be the most preferable items to the farmers because of easy formulation process with common utensils. Good marketing linkage and requirement of capital had been identified as the prerequisites for operating small-scale business on value-added fish products.

Characterization of the benthos, marine debris and bottom fish at Gray’s Reef National Marine Sanctuary

Executive Summary: Baseline characterization of resources is an essential part of marine protected area (MPA) management and is critical to inform adaptive management. Gray’s Reef National Marine Sanctuary (GRNMS) currently lacks adequate characterization of several key resources as identified in the 2006 Final Management Plan. The objectives of this characterization were to fulfill this need by characterizing the bottom fish, benthic features, marine debris, and the relationships among them for the different bottom types within the sanctuary: ledges, sparse live bottom, rippled sand, and flat sand. Particular attention was given to characterizing the different ledge types, their fish communities, and the marine debris associated with them given the importance of this bottom type to the sanctuary. The characterization has been divided into four sections. Section 1 provides a brief overview of the project, its relevance to sanctuary needs, methods of site selection, and general field procedures. Section 2 provides the survey methods, results, discussion, and recommendations for monitoring specific to the benthic characterization. Section 3 describes the characterization of marine debris. Section 4 is specific to the characterization of bottom fish. Field surveys were conducted during August 2004, May 2005, and August 2005. A total of 179 surveys were completed over ledge bottom (n=92), sparse live bottom (n=51), flat sand (n=20), and rippled sand (n=16). There were three components to each field survey: fish counting, benthic assessment, and quantification of marine debris. All components occurred within a 25 x 4 m belt transect. Two divers performed the transect at each survey site. One diver was responsible for identification of fish species, size, and abundance using a visual survey. The second diver was responsible for characterization of benthic features using five randomly placed 1 m2 quadrats, measuring ledge height and other benthic structures, and quantifying marine debris within the entire transect. GRNMS is composed of four main bottom types: flat sand, rippled sand, sparsely colonized live bottom, and densely colonized live bottom (ledges). Independent evaluation of the thematic accuracy of the GRNMS benthic map produced by Kendall et al. (2005) revealed high overall accuracy (93%). Most discrepancies between map and diver classification occurred during August 2004 and likely can be attributed to several factors, including actual map or diver errors, and changes in the bottom type due to physical forces. The four bottom types have distinct physical and biological characteristics. Flat and rippled sand bottom types were composed primarily of sand substrate and secondarily shell rubble. Flat sand and rippled sand bottom types were characterized by low percent cover (0-2%) of benthic organisms at all sites. Although the sand bottom types were largely devoid of epifauna, numerous burrows indicate the presence of infaunal organisms. Sparse live bottom and ledges were colonized by macroalgae and numerous invertebrates, including coral, gorgonians, sponges, and “other” benthic species (such as tunicates, anemones, and bryozoans). Ledges and sparse live bottom were similar in terms of diversity (H’) given the level of classification used here. However, percent cover of benthic species, with the exception of gorgonians, was significantly greater on ledge than on sparse live bottom. Percent biotic cover at sparse live bottom ranged from 0.7-26.3%, but was greater than 10% at only 7 out of 51 sites. Colonization on sparse live bottom is likely inhibited by shifting sands, as most sites were covered in a layer of sediment up to several centimeters thick. On ledge bottom type, percent cover ranged from 0.42-100%, with the highest percent cover at ledges in the central and south-central region of GRNMS. Biotic cover on ledges is influenced by local ledge characteristics. Cluster analysis of ledge dimensions (total height, undercut height, undercut width) resulted in three main categories of ledges, which were classified as short, medium, and tall. Median total percent cover was 97.6%, 75.1%, and 17.7% on tall, medium, and short ledges, respectively. Total percent cover and cover of macroalgae, sponges, and other organisms was significantly lower on short ledges compared to medium and tall ledges, but did not vary significantly between medium and tall ledges. Like sparse live bottom, short ledges may be susceptible to burial by sand, however the results indicate that ledge height may only be important to a certain threshold. There are likely other factors not considered here that also influence spatial distribution and community structure (e.g., small scale complexity, ocean currents, differential settlement patterns, and biological interactions). GRNMS is a popular site for recreational fishing and boating, and there has been increased concern about the accumulation of debris in the sanctuary and potential effects on sanctuary resources. Understanding the types, abundance, and distribution of debris is essential to improving debris removal and education efforts. Approximately two-thirds of all observed debris items found during the field surveys were fishing gear, and about half of the fishing related debris was monofilament fishing line. Other fishing related debris included leaders and spear gun parts, and non-gear debris included cans, bottles, and rope. The spatial distribution of debris was concentrated in the center of the sanctuary and was most frequently associated with ledges rather than at other bottom types. Several factors may contribute to this observation. Ledges are often targeted by fishermen due to the association of recreationally important fish species with this bottom type. In addition, ledges are structurally complex and are often densely colonized by biota, providing numerous places for debris to become stuck or entangled. Analysis of observed boat locations indicated that higher boat activity, which is an indication of fishing, occurs in the center of the sanctuary. On ledges, the presence and abundance of debris was significantly related to observed boat density and physiographic features including ledge height, ledge area, and percent cover. While it is likely that most fishing related debris originates from boats inside the sanctuary, preliminary investigation of ocean current data indicate that currents may influence the distribution and local retention of more mobile items. Fish communities at GRNMS are closely linked to benthic habitats. A list of species encountered, probability of occurrence, abundance, and biomass by habitat is provided. Species richness, diversity, composition, abundance, and biomass of fish all showed striking differences depending on bottom type with ledges showing the highest values of nearly all metrics. Species membership was distinctly separated by bottom type as well, although very short, sparsely colonized ledges often had a similar community composition to that of sparse live bottom. Analysis of fish communities at ledges alone indicated that species richness and total abundance of fish were positively related to total percent cover of sessile invertebrates and ledge height. Either ledge attribute was sufficient to result in high abundance or species richness of fish. Fish diversity (H`) was negatively correlated with undercut height due to schools of fish species that utilize ledge undercuts such as Pareques species. Concurrent analysis of ledge types and fish communities indicated that there are five distinct combinations of ledge type and species assemblage. These include, 1) short ledges with little or no undercut that lacked many of the undercut associated species except Urophycis earlii ; 2) tall, heavily colonized, deeply undercut ledges typically with Archosargus probatocephalus, Mycteroperca sp., and Pareques sp.; 3) tall, heavily colonized but less undercut with high occurrence of Lagodon rhomboides and Balistes capriscus; 4) short, heavily colonized ledges typically with Centropristis ocyurus, Halichoeres caudalis, and Stenotomus sp.; and 5) tall, heavily colonized, less undercut typically with Archosargus probatocephalus, Caranx crysos and Seriola sp.. Higher levels of boating activity and presumably fishing pressure did not appear to influence species composition or abundance at the community level although individual species appeared affected. These results indicate that merely knowing the basic characteristics of a ledge such as total height, undercut width, and percent cover of sessile invertebrates would allow good prediction of not only species richness and abundance of fish but also which particular fish species assemblages are likely to occur there. Comparisons with prior studies indicate some major changes in the fish community at GRNMS over the last two decades although the causes of the changes are unknown. Species of interest to recreational fishermen including Centropristis striata, Mycteroperca microlepis, and Mycteroperca phenax were examined in relation to bottom features, areas of assumed high versus low fishing pressure, and spatial dispersion. Both Mycteroperca species were found more frequently when undercut height of ledges was taller. They often were found together in small mixed species groups at ledges in the north central and southwest central regions of the sanctuary. Both had lower mode size and proportion of fish above the fishery size limit in heavily fished areas of the sanctuary (i.e. high boat density) despite the presence of better habitat in that region. Black sea bass, C. striata, occurred at 98% of the ledges surveyed and appeared to be evenly distributed throughout the sanctuary. Abundance was best explained by a positive relationship with percent cover of sessile biota but was also negatively related to presence of either Mycteroperca species. This may be due to predation by the Mycteroperca species or avoidance of sites where they are present by C. striata. Suggestions for monitoring bottom features, marine debris, and bottom fish at GRNMS are provided at the end of each chapter. The present assessment has established quantitative baseline characteristics of many of the key resources and use issues at GRNMS. The methods can be used as a model for future assessments to track the trajectory of GRNMS resources. Belt transects are ideally suited to providing efficient and quantitative assessment of bottom features, debris, and fish at GRNMS. The limited visibility, sensitivity of sessile biota, and linear nature of ledge habitats greatly diminish the utility of other sampling techniques. Ledges should receive the bulk of future characterization effort due to their importance to the sanctuary and high variability in physical structure, benthic composition, and fish assemblages. (PDF contains 107 pages.)

A comparison of seafloor habitats and associated benthic fauna in areas open and closed to bottom trawling along the central California Continental Shelf

Executive Summary: A number of studies have shown that mobile, bottom-contact fishing gear (such as otter trawls) can alter seafloor habitats and associated biota. Considerably less is known about the recovery of these resources following such disturbances, though this information is critical for successful management. In part, this paucity of information can be attributed to the lack of access to adequate control sites – areas of the seafloor that are closed to fishing activity. Recent closures along the coast of central California provide an excellent opportunity to track the recovery of historically trawled areas and to compare recovery rates to adjacent areas that continue to be trawled. In June 2006 we initiated a multi-year study of the recovery of seafloor microhabitats and associated benthic fauna inside and outside two new Essential Fish Habitat (EFH) closures within the Cordell Bank and Gulf of the Farallones National Marine Sanctuaries. Study sites inside the EFH closure at Cordell Bank were located in historically active areas of fishing effort, which had not been trawled since 2003. Sites outside the EFH closure in the Gulf of Farallones were located in an area that continues to be actively trawled. All sites were located in unconsolidated sands at equivalent water depths. Video and still photographic data collected via a remotely operated vehicle (ROV) were used to quantify the abundance, richness, and diversity of microhabitats and epifaunal macro-invertebrates at recovering and actively trawled sites, while bottom grabs and conductivity/temperature/depth (CTD) casts were used to quantify infaunal diversity and to characterize local environmental conditions. Analysis of still photos found differences in common seafloor microhabitats between the recovering and actively trawled areas, while analysis of videographic data indicated that biogenic mound and biogenic depression microhabitats were significantly less abundant at trawled sites. Each of these features provides structure with which demersal fishes, across a wide range of size classes, have been observed to associate. Epifaunal macro-invertebrates were sparsely distributed and occurred in low numbers in both treatments. However, their total abundance was significantly different between treatments, which was attributable to lower densities at trawled sites. In addition, the dominant taxa were different between the two sites. Patchily-distributed buried brittle stars dominated the recovering site, and sea whips (Halipteris cf. willemoesi) were most numerous at the trawled site though they occurred in only five of ten transects. Numerical classification (cluster analysis) of the infaunal samples also revealed a clear difference between benthic assemblages in the recovering vs. trawled areas due to differences in the relative abundances of component species. There were no major differences in infaunal species richness, H′ diversity, or J′ evenness between recovering vs. trawled site groups. However, total infaunal abundance showed a significant difference attributable to much lower densities at trawled sites. This pattern was driven largely by the small oweniid polychaete Myriochele gracilis, which was the most abundant species in the overall study region though significantly less abundant at trawled sites. Other taxa that were significantly less abundant at trawled sites included the polychaete M. olgae and the polychaete family Terebellidae. In contrast, the thyasirid bivalve Axinopsida serricata and the polychaetes Spiophanes spp. (mostly S. duplex), Prionospio spp., and Scoloplos armiger all had significantly to near significantly higher abundances at trawled sites. As a result of such contrasting species patterns, there also was a significant difference in the overall dominance structure of infaunal assemblages between the two treatments. It is suggested that the observed biological patterns were the result of trawling impacts and varying levels of recovery due to the difference in trawling status between the two areas. The EFH closure was established in June 2006, within a month of when sampling was conducted for the present study, however, the stations within this closure area are at sites that actually have experienced little trawling since 2003, based on National Marine Fishery Service trawl records. Thus, the three-year period would be sufficient time for some post-trawling changes to have occurred. Other results from this study (e.g., similarly moderate numbers of infaunal species in both areas that are lower than values recorded elsewhere in comparable habitats along the California continental shelf) also indicate that recovery within the closure area is not yet complete. Additional sampling is needed to evaluate subsequent recovery trends and persistence of effects. Furthermore, to date, the study has been limited to unconsolidated substrates. Ultimately, the goal of this project is to characterize the recovery trajectories of a wide spectrum of seafloor habitats and communities and to link that recovery to the dynamics of exploited marine fishes. (PDF has 48 pages.)

A pilot study of hogfish (Lachnolaimus maximus Walbaum 1792) movement in the Conch Reef Research Only Area (northern Florida Keys)

The largely sedentary behavior of many fishes on coral reefs is well established. Information on the movement behavior of individual fish, over fine temporal and spatial scales, however, continues to be limited. It is precisely this type of information that is critical for evaluating the success of marine reserves designed for the conservation and/or management of vagile fishes. In this pilot study we surgically-tagged eight hogfish (Lachnolaimus maximus Walbaum 1792) with coded-acoustic transmitters inside the Conch Reef Research Only Area (a no-take marine reserve) in the northern Florida Keys National Marine Sanctuary. Our primary objective was to characterize the movement of L. maximus across Conch Reef in the vicinity of the reserve. All fish were captured, surgically-tagged and released in situ during a saturation mission to the Aquarius Undersea Laboratory, which is located in the center of the reserve. Movement of tagged L. maximus was recorded for up to 95 days by three acoustic receivers deployed on the seafloor. Results showed clear diel patterns in L. maximus activity and regular movement among the receivers was recorded for seven of the eight tagged fish. Fidelity of tagged fish to the area of release was high when calculated at the scale of days, while within-day fidelity was comparatively low when calculated at the scale of hours. While the number of fish departures from the array also varied, the majority of departures for seven of the eight fish did not exceed 1-hr (with the exception of one 47-day departure), suggesting that when departures occurred, the fish did not travel far. Future efforts will significantly expand the number of receivers at Conch Reef such that fish movement behavior relative to the reserve boundaries can be quantified with increased temporal and spatial resolution. (PDF contains 22 pages.)

Maintaining the "public good" nature of improved fish strains: dissemination of knowledge and materials

Many sources of information that discuss currents problems of food security point to the importance of farmed fish as an ideal food source that can be grown by poor farmers, (Asian Development Bank 2004). Furthermore, the development of improved strains of fish suitable for low-input aquaculture such as Tilapia, has demonstrated the feasibility of an approach that combines “cutting edge science” with accessible technology, as a means for improving the nutrition and livelihoods of both the urban poor and poor farmers in developing countries (Mair et al. 2002). However, the use of improved strains of fish as a means of reducing hunger and improving livelihoods has proved to be difficult to sustain, especially as a public good, when external (development) funding sources devoted to this area are minimal1. In addition, the more complicated problem of delivery of an aquaculture system, not just improved fish strains and the technology, can present difficulties and may go explicitly unrecognized (from Sissel Rogne, as cited by Silje Rem 2002). Thus, the involvement of private partners has featured prominently in the strategy for transferring to the public technology related to improved Tilapia strains. Partnering with the private sector in delivery schemes to the poor should take into account both the public goods aspect and the requirement that the traits selected for breeding “improved” strains meet the actual needs of the resource poor farmer. Other dissemination approaches involving the public sector may require a large investment in capacity building. However, the use of public sector institutions as delivery agents encourages the maintaining of the “public good” nature of the products.

Catch rates as indices of abundance of yellowfin tuna, Thunnus albacares, in the Eastern Pacific Ocean

ENGLISH: Catch and effort data from logbooks of tuna seiners were used to make estimates of catch per hour of searching for 1970-1980. The estimates were standardized using a regression model to make annual estimates of abundance adjusted for fishing mode, speed, capacity, use of aerial assistance, net dimensions, and sea-surface temperature. Inside the CYRA the standardized estimates for tuna schools associated with dolphins and those for schools not associated with dolphins showed a similar overall pattern of decline. The 1980 catch rates were about 300/0 of the 1970 rates, the decline being greater for the schools not associated with dolphins. Dolphin-associated schools outside the CYRA declined to about 60% of the 1970 levels. SPANISH: Se emplearon los datos de la captura y el esfuerzo de los cuadernos de bitácora de las embarcaciones cerqueras para hacer las estimaciones de la captura por hora de búsqueda correspondientes a 1970-1980. Se normalizaron estas estimaciones usando un modelo de regresión con el fin' de hacer las estimaciones anuales de la abundancia, ajustadas según la moda de pesca, velocidad, capacidad, uso de ayuda aérea, dimensiones de la red y temperatura de la superficie del mar. En el ARCAA las estimaciones normalizadas de los cardúmenes de atún asociados con delfines y aquellas de los cardúmenes no asociados con delfines, indicaron una pauta general similar de reducción. Las proporciones de captura de 1980, fueron cerca del 300/0 de las de 1970, encontrándose la mayor reducción en los cardúmenes no asociados con delfines. Los cardúmenes asociados con delfines, fuera del ARCAA, se redujeron en un 60% con respecto a los niveles de 1970. (PDF contains 79 pages.)

Habitat enhancing marine structures: Creating habitat in urban waters

Although maritime regions support a large portion of the world’s human population, their value as habitat for other species is overlooked. Urban structures that are built in the marine environment are not designed or managed for the habitat they provide, and are built without considering the communities of marine organisms that could colonize them (Clynick et al., 2008). However, the urban waterfront may be capable of supporting a significant proportion of regional aquatic biodiversity (Duffy-Anderson et al., 2003). While urban shorelines will never return to their original condition, some scientists think that the habitat quality of urban waterfronts could be significantly improved through further research and some design modifications, and that many opportunities exist to make these modifications (Russel et al., 1983, Goff, 2008). Habitat enhancing marine structures (or HEMS) are a potentially promising approach to address the impact of cities on marine organisms including habitat fragmentation and degradation. HEMS are a type of habitat improvement project that are ecologically engineered to improve the habitat quality of urban marine structures such as bulkheads and docks for marine organisms. More specifically, HEMS attempt to improve or enhance the physical habitat that organisms depend on for survival in the inter- and sub-tidal waterfronts of densely populated areas. HEMS projects are targeted at areas where human-made structures cannot be significantly altered or removed. While these techniques can be used in suburban or rural areas restoration or removal is preferred in these settings, and HEMS are resorted to only if removal of the human-made structure is not an option. Recent research supports the use of HEMS projects. Researchers have examined the communities found on urban structures including docks, bulkheads, and breakwaters. Complete community shifts have been observed where the natural shoreline was sandy, silty, or muddy. There is also evidence of declines in community composition, ecosystem functioning, and increases in non-native species abundances in assemblages on urban marine structures. Researchers have identified two key differences between these substrates including the slope (seawalls are vertical; rocky shores contain multiple slopes) and microhabitat availability (seawalls have very little; rocky shores contain many different types). In response, researchers have suggested designing and building seawalls with gentler slopes or a combination of horizontal and vertical surfaces. Researchers have also suggested incorporating microhabitat, including cavities designed to retain water during low tide, crevices, and other analogous features (Chapman, 2003; Moreira et al., 2006) (PDF contains 4 pages)

A survey of river habitats on the River Lune

A survey of the River Lune using River Habitat Survey (RHS) was carried out at 103 sections in February/March 99, to which were added 37 sites surveyed between 1994 -1996. Summary statistics were produced on the distribution and extent of flow features (e.g. riffles, pools, rapids etc.), substrate types, tree and associated features and bank profiles. Information on land-use and management was also included in the analyses. A Habitat Modification Score (HMS) describing the level of habitat modification was derived for each site and compared to the whole reference network and to rivers of similar types in Britain. The HMS shows that more than 70% of the sites on the catchment are predominantly unmodified and very few sites are significantly modified. Highly modified sites are concentrated in the urban areas and on the tributaries.

Report on the 1995 stock assessment of the Douglas catchment

The River Douglas has a long industrial heritage beginning in the early 18th century with its use by boats carrying goods between Wigan and Tarleton. The River and its tributaries have also historically been, and to a certain extent are still, subject to polluting inputs from the urban, agricultural and industrialised areas located within its catchment. During the early stages in the production of the River Douglas Catchment Management Plan, it became apparent that very little data existed on the populations of coarse and salmonid fish species within the River Douglas system. The data that did exist was largely anecdotal, consisting of catch reports from anglers or water bailiffs, or of dead and distressed fish following pollution incidents. This study was initiated to assess the status of coarse and salmonid fish species within the River Douglas system and so address the lack of knowledge. Eighty two sites were surveyed by electric fishing, including 14 sites using an electric fishing punt and up to four anodes. The data was analysed according to a new National Fisheries Classification Scheme. This classified the sites by the fish stock s present and compared the results with a database containing information from sites around the country that have similar habitat types. A stocking experiment was also undertaken in the River Lostock using chub reared at the Leyland Hatchery. These were marked with an identifiable blue spot in the spring of 1995 and then released into three, previously surveyed, locations in the river. These sites were then resurveyed during the summer stock assessment. This report also Site Reports with details on monitored sites, habitat features and fishery classification.

Effects of a large fishing closure on benthic communities in the western Gulf of Maine: recovery from the effects of gillnets and otter trawls

The recovery of benthic communities inside the western Gulf of Maine fishing closure area was evaluated by comparing invertebrate assemblages at sites inside and outside of the closure four to six years after the closure was established. The major restriction imposed by the closure was a year-round prohibition of bottom gillnets and otter trawls. A total of 163 seafloor sites (~half inside and half outside the closure) within a 515-km2 study area were sampled with some combination of Shipek grab, Wildco box corer, or underwater video. Bottom types ranged from mud (silt and clay) to boulders, and the effects of the closure on univariate measures (total density, biomass, taxonomic richness) of benthos varied widely among sediment types. For sites with predominantly mud sediments, there were mixed effects on inside and outside infauna and no effect on epifauna. For sites with mainly sand sediments, there were higher density, biomass, and taxonomic richness for infauna inside the closure, but no significant effects on epifauna. For sites dominated by gravel (which included boulders in some areas), there were no effects on infauna but strong effects on epifaunal density and taxonomic richness. For fishing gear, the data indicated that infauna recovered in sand from the impacts of otter trawls operated inside the closure but that they did not recover in mud, and that epifauna recovered on gravel bottoms from the impact of gillnets used inside the closure. The magnitudes of impact and recovery, however, cannot be inferred directly from our data because of a confounding factor of different fishing intensities outside the closure for a direct comparison of preclosure and postclosure data. The overall negative impact of trawls is likely underestimated by our data, whereas the negative impact of gillnets is likely overestimated.

Onshore-offshore distribution and abundance of tuna larvae (Pisces: Scombridae: Thunnini) in near-reef waters of the Coral Sea

The on-offshore distributions of tuna larvae in near-reef waters of the Coral Sea, near Lizard Island (14°30ʹS, 145°27ʹE), Australia, were investigated during four cruises from November 1984 to February 1985 to test the hypothesis that larvae of these oceanic fishes are found in highest abundance near coral reefs. Oblique bongo net tows were made in five on-offshore blocks in the Coral Sea, ranging from 0–18.5 km offshore of the outer reefs of the Great Barrier Reef, as well as inside the Great Barrier Reef Lagoon. The smallest individuals (<3.2 mm SL) of the genus Thunnus could not be identified to species, and are referred to as Thunnus spp. We found species-specific distributional patterns. Thunnus spp. and T. alalunga (albacore) larvae were most abundant (up to 68 larvae/100 m2) in near-reef (0–5.5 km offshore) waters, whereas Katsuwonus pelamis (skipjack tuna) larvae increased in abundance in the offshore direction (up to 228 larvae/100 m2, 11.1–18.5 km offshore). Larvae of T. albacares (yellowfin tuna) and Euthynnus affinis (kawakawa) were relatively rare throughout the study region, and the patterns of their distributions were inconclusive. Few larvae of any tuna species were found in the lagoon. Size-frequency distributions revealed a greater proportion of small larvae inshore compared to offshore for K. pelamis and T. albacares. The absence of significant differences in size-frequency distributions for other species and during the other cruises was most likely due to the low numbers of larvae. Larval distributions probably resulted from a combination of patterns of spawning and vertical distribution, combined with wind-driven onshore advection and downwelling on the seaward side of the outer reefs.

Habitat and bycatch effects on population parameters of inshore lizardfish (Synodus foetens) in the north central Gulf of Mexico

We examined the effect of habitat and shrimp trawl bycatch on the density, size, growth, and mortality of inshore lizardfish (Synodus foetens), a nonexploited species that is among the most widespread and abundant benthic fishes in the north central Gulf of Mexico. Results of quarterly trawl sampling conducted from spring 2004 through spring 2005 revealed that inshore lizardfish are most abundant on sand habitat, but larger fish are more common on shell rubble habitat. There was no significant difference in fish density between habitats exposed to shrimp trawling on the open shelf versus those habitats within a permitted artificial reef zone that served as a de facto no-trawl area; this finding indicates that either inshore lizardfish experienced minimal effects from trawling or, more likely, that fish moved between trawled and nontrawled habitats. Exploitation ratio (bycatch mortality/total morality) estimates derived from catch curve analysis ranged from 0.43 inside the artificial reef zone to 0.55 outside the reef zone, thus indicating that inshore lizardfish are subject to significant fishing mortality in the north central Gulf of Mexico despite the lack of a directed fishery for the species. We infer from this result that effects of shrimp trawl bycatch may be significant at the population level for nonexploited species and that a broader ecosystem-scale examination of bycatch effects is warranted.

The Bay Scallop, Argopecten irradians, Massachusetts Through North Carolina: Its Biology and the History of Its Habitats and Fisheries

This article covers the biology and the history of the bay scallop habitats and fishery from Massachusetts to North Carolina. The scallop species that ranges from Massachusetts to New York is Argopecten irradians irradians. In New Jersey, this species grades into A. i. concentricus, which then ranges from Maryland though North Carolina. Bay scallops inhabit broad, shallow bays usually containing eelgrass meadows, an important component in their habitat. Eelgrass appears to be a factor in the production of scallop larvae and also the protection of juveniles, especially, from predation. Bay scallops spawn during the warm months and live for 18–30 months. Only two generations of scallops are present at any time. The abundances of each vary widely among bays and years. Scallops were harvested along with other mollusks on a small scale by Native Americans. During most of the 1800’s, people of European descent gathered them at wading depths or from beaches where storms had washed them ashore. Scallop shells were also and continue to be commonly used in ornaments. Some fishing for bay scallops began in the 1850’s and 1860’s, when the A-frame dredge became available and markets were being developed for the large, white, tasty scallop adductor muscles, and by the 1870’s commercial-scale fishing was underway. This has always been a cold-season fishery: scallops achieve full size by late fall, and the eyes or hearts (adductor muscles) remain preserved in the cold weather while enroute by trains and trucks to city markets. The first boats used were sailing catboats and sloops in New England and New York. To a lesser extent, scallops probably were also harvested by using push nets, picking them up with scoop nets, and anchor-roading. In the 1910’s and 1920’s, the sails on catboats were replaced with gasoline engines. By the mid 1940’s, outboard motors became more available and with them the numbers of fishermen increased. The increases consisted of parttimers who took leaves of 2–4 weeks from their regular jobs to earn extra money. In the years when scallops were abundant on local beds, the fishery employed as many as 10–50% of the towns’ workforces for a month or two. As scallops are a higher-priced commodity, the fishery could bring a substantial amount of money into the local economies. Massachusetts was the leading state in scallop landings. In the early 1980’s, its annual landings averaged about 190,000 bu/yr, while New York and North Carolina each landed about 45,000 bu/yr. Landings in the other states in earlier years were much smaller than in these three states. Bay scallop landings from Massachusetts to New York have fallen sharply since 1985, when a picoplankton, termed “brown tide,” bloomed densely and killed most scallops as well as extensive meadows of eelgrass. The landings have remained low, large meadows of eelgrass have declined in size, apparently the species of phytoplankton the scallops use as food has changed in composition and in seasonal abundance, and the abundances of predators have increased. The North Carolina landings have fallen since cownose rays, Rhinoptera bonsais, became abundant and consumed most scallops every year before the fishermen could harvest them. The only areas where the scallop fishery remains consistently viable, though smaller by 60–70%, are Martha’s Vineyard, Nantucket, Mass., and inside the coastal inlets in southwestern Long Island, N.Y.