The influence of dredge design on the catch of Callista chione (Linnaeus, 1758)

To evaluate a possible introduction of a new dredge in the fishery of Callista chione (Linnaeus, 1758), IPIMAR has conducted a study with the objective of comparing the efficiency of two dredges (traditional dredge and the new dredge design) and evaluating their impact on the benthic community. The experiments were carried out during March 1999 on the Southwest coast of Portugal, from a site off Troia. Three different tow durations of 5, 10 and 20 min were investigated. A total of 24 hauls were accomplished, 4 for each tow duration and dredge. The experiments were conducted by attaching a cover bag with a 20 mm mesh to the gear. After each haul, the catches in the bag and in the cover were sorted separately. All individuals retained were attributed scores on a scale of 1–4 in which 1 equates to good and 4 equates to dead. The results obtained showed that catches from the traditional dredge (TD) are composed of a great fraction of juveniles of C. chione, while in the new dredge (NDD) catches are composed, almost entirely, by individuals with a superior size to the minimum legal length (50 mm). This result indicates that the mesh of the bag of the TD used in the exploitation of this resource is not adequate. For the 3 different tow durations, the mean fishing yield obtained for the NDD was always superior to the TD, due to its greater efficiency in capture. The proportion of by-catch is significantly higher when the TD is used. For all 3 tow duration, the TD caused mortalities on the target species and on the macrobenthic community in the same order of magnitude as the NDD. Since the fishery of C. chione is managed by daily quotas per boat, when using the NDD the impact on the macrobenthic community is reduced by about 50% due to its greater efficiency of capture. Another advantage in the usage of the NDD relatively to the TD, is to allow the smallest individuals (independently of the species) to escape rapidly through the metallic bars on the grid, increasing their probability of survival.     

Growth statistics of an exploited razor clam (Ensis siliqua) bed at Gormanstown,Co Meath,Ireland

A clam bed of 21 km² was discovered at Gormanstown on the East coast of Ireland in 1997. Between July 1998 and August 1999, dredge samples were collected from vessels fishing there and these provided material for biological analysis. E. siliqua occurs with an inshore invertebrate fauna; occasional occurrences of large numbers of Donax vittaus, Pharus legumen and Lanice conchilega were associated with razor clams of less than 6 cm long. As harvesting proceeded smaller individuals appeared in the samples; these may have immigrated onto the bed from the periphery of high densities of larger clams. On the clam bed the animals ranged from 0+ to 19+ years old. Ensis siliqua grew at a slower rate on the west coast of the Irish Sea than on the coast of North Wales. Males grew slightly faster and longer than females and males were more numerous in the landings. The clams are estimated to commence maturation at approximately 4 years of age. They have a similar gonadal cycle to those in Portugal and a similar spawning period from mid-May to the end of July or early August. Condition reflects gonad development, reaching a peak in May. Harvesting by hydraulic dredging causes breakages which are higher in quarters 1 and 4 than in quarters 2 and 3. Bruised razor clams do not eliminate sand in desanding tanks and so they are rejected by processors. The total biomass of the Gormanstown bed is estimated at approximately 1500 tonnes of which 2/3 had been removed by July 1999, two years after exploitation commenced.     

Sub-lethal effects of off-road vehicles (ORVs) on surf clams on sandy beaches

Ecological impacts of vehicle traffic are a significant environmental management issue on many sandy shores. Impacts usually focus on lethal effects of vehicles to organisms, but sub-lethal effects which could reduce the fitness of macrofauna populations are equally possible but unknown. Consequently, we measured changes in body condition and burrowing performance of the beach clam Donax deltoides subjected to vehicle traffic on sandy shores in eastern Australia. Body mass index of clams on beaches open to traffic was 16% lower, but gonadosomatic index and relative valve thickness were not consistently linked to vehicle access to beaches. By contrast, off-road vehicles significantly impaired the burrowing performance of clams. After experimental exposure to ORV traffic (30 passes) and dislodgement from the sediment, the time taken for clams to re-bury into the sand doubled irrespective of the vehicle weight used. Because burrowing is such a critical function in the behavioural repertoire of sandy beach animals, the traffic-induced changes to organisms' performance found in this study may increase mortality by causing displacement to less favourable habitats by swash, and by intensifying the risk of predation and desiccation. When assessing the ecological impacts of vehicles on beach fauna, it is thus important to consider both lethal and sub-lethal effects.     

An overview of historical changes in the fishing gear and practices of pelagic longliners,with particular reference to Japan’s Pacific fleet

We identify changes in pelagic longline fishing gear and practices that need to be accounted for in stock assessments. Pelagic longline fishers have continuously modified their fishing gear and practices to improve fishing power and catchability, which has altered the relationship between catch rates and abundance. Advances in technology resulted in the introduction of many electronic devices to assist in navigation, communication and finding target species. The development of synthetic materials allowed improvements to lines and hooks that increased the probability of hooking target species and landing them. Other changes increased fishing power by improving searching efficiency (e.g., satellite imagery) or the time spent on fishing grounds (e.g., freezers). The number of hooks deployed in daily longlining operations has steadily increased since 1950. However, mean soak time did not change significantly because faster longline retrieval and deployment speeds balanced the increased hook numbers. There has been a shift from having all baits available at dawn, to having more available at dusk and at night. In the 1970s, several longline fleets began to exploit a much greater depth range, resulting in increased catchability for deep-dwelling species (e.g., bigeye tuna, Thunnus obesus) and reduced catchability for epipelagic species like blue marlin (Makaira nigricans). Research has been mostly limited to the effects of longline depth on the catchability of target species. Recent experiments have quantified the effects of bycatch mitigation measures on fishing power and catchability. Progressive improvements in expertise and technological improvements in the gear will also affect fishing power, but are particularly difficult to quantify.     

Behavioral responses of minke whales (Balaenoptera acutorostrata) to experimental fishing gear in a coastal environment

Whale entanglement in fishing gear is a global problem, and underwater ropes associated with this gear are often the cause of injuries that can lead to fatalities. Minke whales (Balaenoptera acutorostrata) are especially at risk because they are relatively small, widely distributed, and often occur in coastal habitats where many types of fishing gear are deployed. It is unknown whether minke whales can detect and avoid ropes associated with fishing gear. To address this question we conducted a series of field experiments to measure behavioral responses of nearshore minke whales to underwater ropes simulating crab and whelk fishing gear. We also investigated correlations between whale behaviors and specific environmental variables. Our methods involved both visual and acoustic monitoring of whale behaviors near experimental ropes and buoys of different colors. A remote sensing system was also used to simultaneously monitor oceanographic conditions, record underwater sounds, and capture underwater video of whales swimming near ropes. Minke whales (N = 42) decreased their swimming velocity and altered their bearing when passing near experimental ropes, especially during trials with white and black ropes. Some minkes (N = 7) also altered their underwater swimming trajectories when passing near ropes, and often appeared to produce low-frequency vocalizations. Collectively this information provides strong evidence that minke whales detect and react behaviorally to the presence of underwater ropes that simulate fishing gear in nearshore areas. We hypothesize that visual and perhaps passive acoustic sensory abilities may be the mechanisms behind these rope avoidance behaviors. We recommend that high contrast ropes (white and black) be used with fishing gear in coastal areas to help minimize entanglements of minke and perhaps other whale species.     

The impact of scallop drags on sea urchin populations and benthos in the Bay of Fundy,Canada

The fishery for the green sea urchin (Strongylocentrotus droebachiensis) began in New Brunswick in the late 1980s in response to increasing demand from Asian markets, primarily Japan. Fishing was initiated by members of the scallop industry and the harvesting practices were based on familiar fishing gear (scallop drags or dredges) and similar operations occurring simultaneously in Maine. Because of the potential impact of scallop gear on the shallow water populations in areas not traditionally fished, a study was initiated in 1993 to document (1) the proportion of sea urchins damaged during the harvesting operation, (2) the impact on and subsequent recovery time of the associated benthic flora and epifauna, and (3) the impacts on the bottom substrate. Two sites were chosen for the study based on a split-plot design with a control and experimental plot at each site. In each experimental plot, a towing lane was created parallel to shore. Divers used a fixed line transect method to survey the control and treatment plots prior to and after the harvesting operation done with commercial scallop Digby drags. Further diver-based surveys were done 3 and 6 months later. Results showed a significant decrease in sea urchin densities and an increase in the number of broken sea urchin tests after the harvesting operation at the Passamaquoddy Bay and Grand Manan sites (3–15%). On both sites, there were significant changes in the density of mobile predators such as lobsters, crabs, whelks and sculpins. Lobster density declined to zero after dragging, but the lack of body parts suggested they moved out of the area. Whelks were observed to move into each of the experimental areas, likely in response to probable increase in available food. The dragging operation increased the breakage rate of the kelp, Laminaria longicruris. From the study we concluded that there were short-term impacts from dragging, but the observable effects on the bottom from the single dragging event were gone in less than 3 months. The longer-term effects of dragging were unknown.     

Fishing gears involved in entanglements of minke whales (Balaenoptera acutorostrata) in the East Sea of Korea

Entanglement of marine mammals in fishing gear is a global issue. It is considered a significant threat to minke whales (Balaenoptera acutorostrata) in the East Sea of Korea. A total of 214 entanglements of minke whales in this area between 2004 and 2007 were used to investigate types and parts of fishing gears involved in entanglements. The majority of entanglements were mainly caused by three types of fishing gears: set nets, pots, and gill nets (n= 207, 96.7%). Other entanglements were associated with bottom trawls, purse seines, and trawls. A total of 65 entanglements were attributed to the main and branch lines of fishing gears. The most common body part of minke whales which attached to fishing gears was the mouth (n= 63, 30.4%). Most entanglements took place within 10 nmi from land (n= 179, 86.5%), and between 10 and 220 m of water depth. The mean length of entangled minke whales in set nets was significantly smaller than that of whales in pots and gill nets samples (P < 0.001). Also, the mean body length of minke whales that entangled in the coastal area and shallow waters was significantly shorter than that of whales in the offshore area and deep waters (P < 0.001). This information can be used as fundamental data to conserve and manage this population of minke whales in the East Sea of Korea, and also to modify fishing gear to reduce entanglements. Future studies should focus on investigating the impact of these entanglements on the population and the effectiveness of mitigation measures to reduce entanglements of minke whales in this area.     

The fishery of the Comoros,with comments on its possible impact on coelacanth survival

Synopsis The traditional methods of deepsea handline fishing in the Comoros are described. The main target species is the oilfish Ruvettus pretiosus, and the coelacanth Latimeria chalumnae is caught as a bycatch. In recent years motorised dugout canoes as well as outboard- and inboard-powered boats have been introduced into the fishery, and more efficient fishing tackle has become available. The more modern gear is intended for use on pelagic fishes and has added a new dimension to the fishery. Traditional handline fishermen are not considered to be a threat to the coelacanth, but the fishermen equipped with motorised boats and modern tackle would constitute a real threat if they direct their efforts on inshore reefs.     

Responses of benthic scavengers to fishing disturbance by towed gears in different habitats

The aggregation and feeding behaviour of invertebrate scavengers in areas disturbed by trawling was investigated at three different localities. At each site a fishing disturbance was created using a commercial 4 m beam trawl and scavenger density was quantified using a light beam trawl. At one site two diver surveys were also carried out; along a line fished with a scallop dredge or a beam trawl on two separate occasions. For all experiments the fished and adjacent unfished control areas were sampled before, and at intervals after, the initial fishing disturbance. Sampling with the light beam trawl revealed that hermit crabs Pagurus bernhardus moved into areas which had been fished with a 4 m beam trawl at an experimental site near Anglesey. The density of these hermit crabs increased significantly in the fished area after fishing had taken place, but no change in density occurred in the adjacent control (unfished) area. At two other sites (Red Wharf Bay, Anglesey and a site offshore from Walney Island) there were no detectable increases in scavenger numbers in the fished areas. Furthermore, at the site near Walney Island, numbers of hermit crabs P. bernhardus, swimming crabs Liocarcinus depurator and starfish Asterias rubens actually decreased after fishing. Thus the responses of scavengers to towed fishing gears varied considerably between different communities. At Red Wharf Bay, divers observed similar responses of scavengers to both beam trawl and scallop dredge disturbance. Four predatory species were observed feeding in the fished area; starfish A. rubens, hermit crabs P. bernhardus, brittlestars Ophiura ophiura and whelks Buccinum undatum. These predators fed on damaged bivalves, echinoderms, crustaceans, whelks and polychaetes. The proportion of starfish feeding in the fished area was significantly higher after fishing had taken place. Demersal fishing activities provide food for scavengers in the form of damaged animals which are left in the tracks of the trawl or dredge. The responses of scavengers to fishing disturbance are not always manifested as a large increase in their abundance. It is clear that the magnitude of response varies between species and between habitat types.     

Gear technology in <Emphasis Type="Italic">Nephrops</Emphasis> trawl fisheries

Nets with a small mesh size are required to catch Nephrops norvegicus, consequently large quantities of small whitefish are also caught, and much of this bycatch is undersized and is discarded dead. The main bycatch species are whiting (Merlangius merlangus), haddock (Melanogrammus aeglefinus) and cod (Gadus morhua). Here we summarize the known behavioural reactions of these species towards conventional trawls and review the results of using different trawl modifications to increase selectivity of Nephrops trawls. The trawl modifications are categorised as separator grids, separator and guiding panels, square-mesh panels, capture avoidance designs and codend modification. Finally, the extent to which these developments have been legislated for is discussed including the conditions under which new gear regulations have been introduced. Haddock and whiting rise during the trawling process facilitating their separation from Nephrops and escape, however the behaviour of small fish of these species is less consistent. Cod and Nephrops remain on bottom of the trawl, so to separate these species requires some physical filtering process. Overall, there is currently sufficient technical ability to improve selectivity in Nephrops trawls. The design of choice is dependent on the objectives of managers; for reducing discards but retaining marketable fish, square-mesh panels offer the most useful tool; to eliminate all bycatch and create a single-species fishery, grids and traditional Nephrops trawls show most potential. Whatever the objectives of the new measures, it is likely that a short-term economic impact will follow, and some form of incentive may be required to implement effective measures. A voluntary uptake of new measures by industry is preferable, however, to date, restrictions on fishing opportunities have been necessary to introduce innovative gear designs.     

Sperm whale depredation of sablefish longline gear in the northeast Pacific Ocean

Interactions between marine mammals and fisheries include competition for prey (catch), marine mammal entanglement in fishing gear, and catch removal off fishing gear (depredation). We estimated the magnitude of sperm whale depredation on a major North Pacific longline fishery (sablefish) using data collected during annual longline surveys. Sperm whale depredation occurs while the longline gear is off‐bottom during retrieval. Sperm whales were observed on 16% of longline survey sampling days, mostly (95% of sightings) over the continental slope. Sightings were most common in the central and eastern Gulf of Alaska (98% of sightings), occasional in the western Gulf of Alaska and Aleutian Islands, and absent in the Bering Sea. Longline survey catches were commonly preyed upon when sperm whales were present (65% of sightings), as evidenced by damaged fish. Neither sperm whale presence (P = 0.71) nor depredation rate (P = 0.78) increased significantly from 1998 to 2004. Longline survey catch rates were about 2% less at locations where depredation was observed, but the effect was not significant (P = 0.34). Estimated sperm whale depredation was <1% of the annual sablefish longline fishery catch off Alaska during 1998 to 2004.     

Simulation of the entanglement of a North Atlantic right whale (Eubalaena glacialis) with fixed fishing gear

Population estimates of the critically endangered North Atlantic right whale (Eubalaena glacialis) put the number of individuals at 458 with the actual number likely being lower due to a recent unusual mortality event. Entanglement with fixed fishing gear is the most significant cause of mortality of North Atlantic right whales. There remains little documentation of how North Atlantic right whales become enwrapped during an encounter with fixed fishing gear. In order to gain a better understanding of how entanglements might occur, an interactive simulator was developed that allows the user to swim a virtual whale model using a standard game controller through a gear field in an attempt to re‐create an entanglement. The morphologically accurate right whale model produces realistic swimming motions and is capable of pectoral fin motions in response to user input. Using the simulator, gear entanglements involving the pectoral flippers including ropes wrapping around the body and entanglements involving the tailstock were re‐created. Entanglements involving the pectoral flippers with body wraps were more easily generated than entanglements involving the tailstock only. The simulator should aid scientists, fisheries experts, fishing gear designers, and bycatch reduction scientists in understanding entanglement dynamics and testing potential new gear configurations.     

Types and extent of fishing gear losses and their causes in the artisanal fisheries of Istanbul,Turkey

Fishing gear losses remain a serious problem for marine life; these losses are also the source of an invisible fishing mortality. This study is an analysis of this problem within the artisanal fisheries of Istanbul. From September 2009 through May 2010, face‐to‐face interviews were conducted in 27 fishing ports for a total of 282 questionnaires. Estimates of lost fishing gear were 229.48 km of set nets, 2700 m of longlines, and 14 fish traps. Turbot nets had the highest loss ratio (54.73%), followed by bonito nets (16%), red mullet nets (7.36%), and encircling trammel nets (4.83%). The four major causes of net loss were: conflicts with other gear types (trawl and purse seine), conflicts with cargo vessels, bottom structure hindrances, and bad weather conditions. Bottom structures were the single factor in net losses for longlines and fish traps. The study observed that large quantities of nets had been lost, and that each net type showed a positive relationship between the number of nets used and the number of nets lost. Separate zones for artisanal and industrial fisheries are recommended as a realistic approach to reduce the losses of fishing gear and the impact of ‘ghost fishing’.     

Biases in determining the diet of jumbo squid <Emphasis Type="Italic">Dosidicus gigas</Emphasis> (D’ Orbigny 1835) (Cephalopoda: Ommastrephidae) off southern-central Chile (34°S–40°S)

The diet of jumbo squid (Dosidicus gigas) off southern-central Chile is described to examine potential biases in the determination of their main prey. Specimens were collected from catches using different fishing gear (jigging, trawl and purse-seine), from July 2003 to January 2004, and from December 2005 to October 2006. The stomach contents were analyzed in terms of frequency of occurrence, number, and weight of prey items and the diet composition was analyzed using Detrended Correspondence Analysis. In the industrial purse-seine fleet for jack mackerel (Trachurus murphyi), the dominant prey of D. gigas was T. murphyi. In the industrial mid-trawl fishery for Patagonian grenadier (Macruronus magellanicus), the dominant species in the diet of D. gigas was M. magellanicus. Similarly, Chilean hake (Merluccius gayi) was the main prey in the diet of D. gigas obtained in the industrial trawl fishery for Chilean hake; and, in both artisanal fisheries (purse-seine for small pelagics and jigging), small pelagic fish and D. gigas were the main prey in the stomach contents of D. gigas. Cannibalism in D. gigas varied between different fleets and probably is related to stress behavior during fishing. The Detrended Correspondence Analysis ordination showed that the main prey in the diet of D. gigas is associated with the target species of the respective fishery. Consequently, biases are associated with fishing gear, leading to an overestimate in the occurrence of the target species in the diet. We recommend analyzing samples from jigging taken at the same time and place where the trawl and purse-seine fleets are operating to avoid this problem, and the application of new tools like stable isotope, heavy metal, and fatty acid signature analyses.     

Present status of the multi‐gear shrimp fishery off the west coast of Sri Lanka: gear‐based species diversity and selectivity

Catch statistics were monitored from well established small‐scale shrimp fisheries in Negombo lagoon and the adjacent coast in western Sri Lanka, in order to evaluate resource usage, gear selectivity, and spatio‐temporal dynamics of catches and CPUE. A total of 55 species, representing 35 families, including 13 shrimp species were recorded from 3546 samples obtained weekly during January 2009‐April 2010, for nine types of gear in six fishing grounds. Special emphasis was on shrimp catches: four main shrimp species, Metapenaeus dobsoni, Fenneropenaeus indicus, Parapenaeopsis coromandelica and Penaeus semisulcatus, represented 82% of the total shrimp landings. Catch per unit effort (CPUE) differed among fishing grounds, months and gear types. Species diversity differed among the gear chosen. Hierarchical cluster analysis based on presence‐absence of the species data of catches showed that clustering was based on habitat rather than on the fishing gear. Species composition analysed with a Detrended Correspondence Analyses over months and fishing grounds showed a distinction of trawl gear from the remainder of the gear operated in the lagoon. The information presented is of importance for evaluation of the present status of the shrimp fishery and for developing management strategies based on the types of gear.     

Recreational fishing depredation and associated behaviors involving common bottlenose dolphins (Tursiops truncatus) in Sarasota Bay,Florida

Odontocete depredation involves stealing or damaging bait or prey already captured by fishing gear. The increase in depredation is of concern for small stocks of cetaceans because interactions with fishing gear can lead to serious injury or mortality through entanglement or ingestion. Using long‐term data sets available for the bottlenose dolphin (Tursiops truncatus) community in Sarasota Bay, Florida, we investigated recreational fishing gear interactions by (1) examining temporal patterns in depredation and associated behaviors from 2000 to 2007; (2) quantifying the behavior of dolphins that depredate or engage in associated behaviors; and (3) identifying factors associated with the rise in depredation locally. The number of incidents of dolphins (primarily adult males) interacting with recreational anglers and boaters increased following 2004. Depredation and associated behaviors increased during red tide lags and tourist seasons during times of prey depletion and heightened angler and boater activity. Dolphins with a history of fishing gear interactions shifted away from natural activity patterns and were more likely to be within 50 m of fishing lines. Recreational fishing gear interactions were attributed to a two percent population decline in Sarasota Bay in 2006 and need to be considered along with other cumulative human impacts in the development of conservation measures for dolphins.     

The effects of seaweed harvesting on fishes: a response

References Rangeley (1994) has argued that sampling biases, errors in experimental design and low statistical power make the conclusion by Black & Miller (1991), that there was no large impact of an experimental harvest of the seaweedAscophyllum nodosum on fishes, unmerited and misleading. Our study was conducted mainly at two sites close to Lower Argyle, southern Nova Scotia, Canada where harvesting ofAscophyllum nodosum has been carried out continuously for 30 years along-side intense and productive shellfish and finfish fisheries. In southern Nova Scotia, on-going removal ofAscophyllum nodosum with mechanical harvesters is about 17% (Sharpe & Semple 1991); planned annual removal in New Brunswick where Rangeley has worked will be only about 5% (Anon. 1993). The context of our investigation was a small-scale (400 m²) but extreme, experimental removal (100%) of the seaweed. Our focus was on fishes that moved into the intertidal zone as the tide rose in the evening and early morning and were caught in trammel nets, and on the fishes that were retained in a fixed seine that was set at high tide in early morning and the fishes removed at the next low tide. Thus, subject to the constraint on the size of the fishes imposed by the nature of our fishing gear with its stretch mesh of 25 mm, we were concerned with the identity and abundance of fishes that moved in and out of the intertidal zone and their behavioural response to the 400 m² patches of habitat that formed our experimental units. The most striking result was the unexpected, low abundance of fishes caught in our gear.     

Fishing gear losses in the Gökova Special Environmental Protection Area (SEPA), eastern Mediterranean,Turkey

This two‐stage study was designed to determine the types and quantities of lost fishing gear and their distribution in the Gökova Special Environmental Protection Area (SEPA), eastern Mediterranean Sea. The study was carried out in approx. 15% of the total Gökova SEPA (7000 hectares), where traditional fishing is intensive. In the first phase of the study, the owners of all fishing boats (about 67% of the local fishermen in Gökova SEPA, n = 56) were interviewed using a structured questionnaire. In the second phase, diving surveys were conducted at 14 locations to locate and identify lost fishing gear, estimate the extent of the loss, and deduce the coherence between the diving survey and the questionnaire data. The questionnaire results showed that 0.84% of gillnets, 3.41% of trammel nets, and 79.2% of longlines were lost during 2007 and that the major cause of gear loss was snagging on bottom structures. In the diving surveys, 22 600 m² (2.26 hectares) of the bottom area were scanned, and an estimated 157 m of gill and trammel nets and 36 280 m of longline nets were located per hectare in the observed area. Moreover, at diving locations D1 and D2, lost trammel and gill nets were ‘ghost fishing’, suggesting that these lost gear should be removed from the ecosystem. A retrieval project coordinated by universities, fishery cooperatives, and NGOs might help accelerate efforts towards the removal of this lost gear.     

Comparative growth and survival of juvenile hard clams,Mercenaria mercenaria,fed commercially available diets

Hobbyist and researchers often use commercially available phytoplankton concentrates to maintain filter feeding organisms held in their ornamental or experimental tanks. This study investigated the nutritional value of 10 products available commercially for juvenile hard clams, Mercenaria mercenaria. Growth and mortality rates in clams fed these products were compared with those found in clams fed fresh cultures of the microalgae Isochrysis galbana, which is considered an industry standard for supporting growth of juvenile bivalves. Our results show a clear difference in feed nutritional value between non‐living and living commercial diets, and among commercial diets advertised as containing live algae. Overall, results showed that juvenile hard clams fed fresh cultures of I. galbana displayed the best growth and lowest mortality rates, followed by those fed the commercial diet DT's Live Marine Phytoplankton. Growth and mortality rates in unfed controls were similar to those found in clams fed commercial non‐living algae mixes or diets advertised as containing live algae (Phyto‐Feast Live product). Results also showed that the nutritional value of fresh algae (I. galbana) cultures is lost rapidly when cultures are maintained at 4°C, suggesting that algae present in some commercial diets may lose their nutritional value during processing or refrigerated storage. The commercial blend, DT's Live Marine Phytoplankton, seems to represent a good substitute to lab grown algae for clams held in ornamental or experimental aquariums. Zoo Biol 0:1–13, 2006. © 2006 Wiley‐Liss, Inc.     

The Substantial First Impact of Bottom Fishing on Rare Biodiversity Hotspots: A Dilemma for Evidence-Based Conservation

This study describes the impact of the first passage of two types of bottom-towed fishing gear on rare protected shellfish-reefs formed by the horse mussel Modiolus modiolus (L.). One of the study sites was trawled and the other was scallop-dredged. Divers collected HD video imagery of epifauna from quadrats at the two study sites and directed infaunal samples from one site.The total number of epifaunal organisms was significantly reduced following a single pass of a trawl (90%) or scallop dredge (59%), as was the diversity of the associated community and the total number of M. modiolus at the trawled site. At both sites declines in anthozoans, hydrozoans, bivalves, echinoderms and ascidians accounted for most of the change. A year later, no recovery was evident at the trawled site and significantly fewer infaunal taxa (polychaetes, malacostracans, bivalves and ophuroids) were recorded in the trawl track.The severity of the two types of impact reflected the undisturbed status of the habitats compared to previous studies. As a ‘priority habitat’ the nature of the impacts described on M. modiolus communities are important to the development of conservation management policy and indicators of condition in Marine Protected Areas (EU Habitats Directive) as well as indicators of ‘Good Environmental Status’ under the European Union Marine Strategy Framework Directive.Conservation managers are under pressure to support decisions with good quality evidence. Elsewhere, indirect studies have shown declines of M. modiolus biogenic communities in fishing grounds. However, given the protected status of the rare habitat, premeditated demonstration of direct impact is unethical or illegal in Marine Protected Areas. This study therefore provides a unique opportunity to investigate the impact from fishing gear whilst at the same time reflecting on the dilemma of evidence-based conservation management.