The fishery for black scabbardfish (Aphanopus carbo Lowe, 1839) in the Portuguese continental slope

The black scabbardfish is a deep-sea teleost species with high commercial interest in the NE Atlantic. While it is caught by large offshore trawlers in the North of Europe, in the south it is captured by artisanal longlines. On the Portuguese continental slope, in the south of ICES Division IXa, a longline fleet has been engaged in the capture of black scabbardfish for more than 20 years. This paper reviews and analyses the features of this fishery from a temporal perspective based on information from different data sources. The fishery is based on the port of Sesimbra, where a family type fishing community strives to keep catches profitable without altering the artisanal features that characterizes the fleet. Although the fleet has experienced some technical improvements through time, the fishing operations and strategy have changed very little. Fishing occurs at particular areas on the slope, where individual vessels have their own fishing grounds. Annual landings surpassed 4,000 tonnes in the early 1990’s, but decreased to nearly 3,000 tonnes and have remained at this level since 2000. The length structure of the landings was stable from 2000 to 2005, with a modal (total length) class of 1,090 mm. Monthly landings per unit effort estimated by a generalized linear model did not present any marked trend for the period 2000–2004. The landings reported in mainland Portugal were compared with the ones from other regions of the ICES area and the different characteristics of the fisheries operating in the north and south of Europe were analysed.     

A new direct method of stock assessment of the loliginid squid

Hydroacoustic research conducted on chokka squid (Loligo reynaudi d’Orbigny, 1845), off the east coast of South Africa from 1994–2005, has led to the development of an innovative stock assessment technique, perhaps applicable to all loliginids that migrate inshore to spawn. This technique combines hydroacoustic biomass estimates made on the spawning concentrations inshore, and minimum biomass estimates made both inshore and offshore using demersal surveys employing the swept-area method. The hydroacoustic estimate uses an improved method to obtain target strength measurements, and squid concentrations are individually mapped from a small boat with a towed transducer. This method may be used even during intense fishing operations because of the manoeuvrability of the small boat inside a tight cluster of fishing vessels. Biomasses of the individual concentrations are then summed. The inshore biomass, also includes dispersed, mature squid migrating between concentrations, this is assessed using a concentration stability factor. The biomass of dispersed squid offshore is again calculated using the swept-area method, a well known demersal survey methodology. The biomass of concentrated (spawning) squid offshore is calculated using the same proportions between concentrated and dispersed squid which were found inshore. All four components are then summed to calculate the total biomass. The result obtained is subject to the effect of complex temporal dynamics, as new animals are recruited to the adult pool and those recently assessed migrate to other sectors of the distribution area.     

Variability of Suitable Habitat of Western Winter-Spring Cohort for Neon Flying Squid in the Northwest Pacific under Anomalous Environments

We developed a habitat suitability index (HSI) model to evaluate the variability of suitable habitat for neon flying squid (Ommastrephes bartramii) under anomalous environments in the Northwest Pacific Ocean. Commercial fisheries data from the Chinese squid-jigging vessels on the traditional fishing ground bounded by 35°-45°N and 150°-175°E from July to November during 1998-2009 were used for analyses, as well as the environmental variables including sea surface temperature (SST), chlorophyll-a (Chl-a) concentration, sea surface height anomaly (SSHA) and sea surface salinity (SSS). Two empirical HSI models (arithmetic mean model, AMM; geometric mean model, GMM) were established according to the frequency distribution of fishing efforts. The AMM model was found to perform better than the GMM model. The AMM-based HSI model was further validated by the fishery and environmental data in 2010. The predicted HSI values in 1998 (high catch), 2008 (average catch) and 2009 (low catch) indicated that the squid habitat quality was strongly associated with the ENSO-induced variability in the oceanic conditions on the fishing ground. The La Niña events in 1998 tended to yield warm SST and favorable range of Chl-a concentration and SSHA, resulting in high-quality habitats for O. bartramii. While the fishing ground in the El Niño year of 2009 experienced anomalous cool waters and unfavorable range of Chl-a concentration and SSHA, leading to relatively low-quality squid habitats. Our findings suggest that the La Niña event in 1998 tended to result in more favorable habitats for O. bartramii in the Northwest Pacific with the gravity centers of fishing efforts falling within the defined suitable habitat and yielding high squid catch; whereas the El Niño event in 2009 yielded less favorable habitat areas with the fishing effort distribution mismatching the suitable habitat and a dramatic decline of the catch of O. bartramii. This study might provide some potentially valuable insights into exploring the relationship between the underlying squid habitat and the inter-annual environmental change.     

Fishery biology of the seven star flying squid Martialia hyadesi at South Georgia during winter

A scientific research fishing expedition targeting the oceanic/slope ommastrephid squid Martialia hyadesi was undertaken by a Korean-registered squid jigger in CCAMLR area 48.3, near South Georgia, in June 1996, providing the first opportunity to collect data on the fishery biology of this species during the austral winter. Fishing took place over a period of 8 days; a series of eight drifts was undertaken along an approximately east/west transect of about 200 nautical miles to the north and west of South Georgia, over depths ranging from 1,700 to 2,713?m. All fishing was to the south of the Antarctic Polar Front. Data were collected on sea surface temperature, catch per unit of effort, size, sex, maturity status and stomach contents of the catch and a sample of squid was aged by counting putative, daily microgrowth increments in the sectioned statolith. All squid were caught by jigs operating at depths from 80 to 100?m to the surface. Catch per unit of effort per drift varied between 1.0 and 21.9?kg?min^?1 and there was no by-catch. Greatest numbers of squid were caught at dusk and dawn. Mantle length fell in the range 220–350?mm (males) and 212–370?mm (females). Most males were sexually mature (Lipinski's stages IV–V) and most females were immature (stage II). The absence of mature females suggests that no spawning takes place in this area during the austral winter. The squid were up to 1?year of age and had hatched during the previous winter. They were apparently from the same cohort as had been sampled at the Antarctic Polar Front in February 1996. Myctophids were the major prey in the stomach contents and the squid Gonatus antarcticus was also important; crustaceans were relatively unimportant. The results suggest that concentrations of Martialia hyadesi are present in the vicinity of South Georgia, south of the Antarctic Polar Front, during the austral winter. The squid are actively feeding during the austral winter and are susceptible to jigging gear.     

Effects of commercial fishing on the population structure of spawning southern calamary (Sepioteuthis australis)

This study explored population dynamics of Sepioteuthis australis on a fine temporal scale before, during, and after a 3-month commercial fishing closure on the summer inshore spawning grounds of Great Oyster Bay, Tasmania, Australia. An abrupt change in male size (mantle length) and population sex ratio after the re-opening of the commercial fishery suggests that fishing alters the population structure on the spawning beds from a ‘natural’ structure which is highly biased towards males, to a more even ratio of males to females. Although jigs are taking a representative sample of the squid population using the spawning beds at any one time, the fishery is apparently still effectively selective for males, potentially as a function of differential spawning movements of the two sexes. Increased fishing pressure over the past 5 years had been correlated with a change towards a highly male-biased sex ratio on the spawning beds; however the current study suggests that increased fishing pressure in recent years may not have reduced the proportion of females. Instead, the inter-annual change in sex ratio may reflect changes in the degree of protection from fishing, with progressively longer closures allowing time for more males to accumulate on the beds and therefore, for the proportion of males to increase (as opposed to a decrease of females). As fishing is selective for males, fishing throughout the spawning season could potentially modify the process of sexual selection and the mating behaviors of the individuals within the spawning population, highlighting the need for closures over this crucial period. Additionally, examinations and comparisons of squid population structure need to be interpreted in light of fishing pressure and broader movement patterns.     

Determinants of temporal trends in size in vessel-based reporting in the USA Illex illecebrosus fishery

The Illex illecebrosus fishery in the northwestern Atlantic Ocean is a trawl‐based fishery. Illex illecebrosus normally lives <1 year, thus managing the fishery using a standard stock assessment approach is difficult. Real‐time management is an attractive option. The purpose of this study was to investigate the utility of data on size composition reported by commercial vessels for application in real‐time management in the I. illecebrosus fishery. Observations were collected from fish processors for 1996–98 and from fishing vessels directly reporting in 1999–2001. Mean size of I. illecebrosus increased more or less steadily through the fishing season in each year. Apparent growth rates, determined by evaluating the change in mean size in the catch, varied considerably between years. Apparent growth rates appear to be reasonable expressions of true growth rates because either the bulk of the squid entered the fishery at the beginning of the fishery and remained with the fishery for the duration of the season, or the squid on the outer shelf, available to the fishery, represented an emigrated portion of a larger coherent offshore population. Depth exerted only a minor influence on the size of squid caught, whereas the size–frequency varied significantly with latitude. Largest squid were caught at the southern and northern extremes of the study domain. Refrigerated seawater (RSW) trawlers consistently caught smaller squid than did freezer trawlers. The complexity of I. illecebrosus size structure revealed by this study indicates the necessity of obtaining a dispersed data set, in space, with a degree of temporal detail to elucidate trends. Such a data set is conceivably obtainable from fishing vessels reporting information as they fish providing that the sampling design addresses issues concerning the dispersion of vessels across latitude, the appropriate composition of the reporting fleet, and the collection of sufficient observations per tow to adequately resolve the range in size as well as the mean.     

The role of life history and behavior in explaining unionid mussel distributions

The São Paulo shelf ranges from ~23°S to 25°S, comprising nearly 622 km of shoreline. This region sustains historical landings of the tropical arrow squid Doryteuthis plei. As in other coleoid cephalopods, the broodstock dies following spawning and the continuance of the population relies exclusively upon the survival of the paralarvae, which are very sensitive to oceanographic conditions. As a first step towards the understanding of paralarval transport, the shelf area was evaluated in terms of retention/dispersion potential. A Lagrangian particle-tracking Individual-Based Model was set up using a 3D Princeton Ocean Model model forced with in situ data obtained from July 2009 to July 2011. Neutrally buoyant particles were released every first day of every month in the model, and tracked for 30 days. The retention potential was high for particles released from the bottom all over the study area from the coast to the shelf break (200 m isobath). Offshore losses showed a marked seasonality. Regarding inshore losses, the percentage of particles beached was constant year round and smaller than offshore losses, being higher south of 24°S. Simulation results seem to agree with present knowledge of the reproductive behaviour of the species in the region.     

Spatial patterns in the biology of the chokka squid, Loligo reynaudii on the Agulhas Bank, South Africa

Although migration patterns for various life history stages of the chokka squid (Loligo reynaudii) have been previously presented, there has been limited comparison of spatial variation in biological parameters. Based on data from research surveys; size ranges of juveniles, subadults and adults on the Agulhas Bank were estimated and presented spatially. The bulk of the results appear to largely support the current acceptance of the life cycle with an annual pattern of squid hatching in the east, migrating westwards to offshore feeding grounds on the Central and Western Agulhas Bank and the west coast and subsequent return migration to the eastern inshore areas to spawn. The number of adult animals in deeper water, particularly in autumn in the central study area probably represents squid spawning in deeper waters and over a greater area than is currently targeted by the fishery. The distribution of life history stages and different feeding areas does not rule out the possibility that discrete populations of L. reynaudii with different biological characteristics inhabit the western and eastern regions of the Agulhas Bank. In this hypothesis, some mixing of the populations does occur but generally squid from the western Agulhas Bank may occur in smaller numbers, grow more slowly and mature at a larger size. Spawning occurs on the western portion of the Agulhas Bank, and juveniles grow and mature on the west coast and the central Agulhas Bank. Future research requirements include the elucidation of the age structure of chokka squid both spatially and temporally, and a comparison of the statolith chemistry and genetic characterisation between adults from different spawning areas across the Agulhas Bank.     

Population structure of the black seabream Spondyliosoma cantharus along the south-west Portuguese coast inferred from otolith chemistry

The chemistry of black seabream Spondyliosoma cantharus otoliths from three main fishery grounds (Olhão, Sagres and Sesimbra) located along c. 400 km of the Portuguese south and west coasts was examined. Element:Ca ratios were determined in whole otoliths and otolith cores of young adult specimens of 2–3 years of age. Using the data from whole otoliths, it was possible to discriminate among S. cantharus from the three fishing grounds with an average accuracy of 91%. Differences among fishing grounds were significant for all element:Ca ratios, and otoliths from Sagres had significantly higher levels of all ratios compared to the other fishing grounds. In contrast, the chemical composition of the otolith core, representative of the larval stage, showed limited variation among the fishing grounds, with an average discrimination accuracy of only 44%, although the Mg:Ca ratio of the otolith cores was also significantly higher for the Sagres samples. The data suggest that larval stages experienced a homogenous environment consistent with an offshore oceanic spawning. Juveniles appeared to display local residency on the inshore fishing grounds, areas probably characterized by greater environmental heterogeneity. Spondyliosoma cantharus population structure is consistent with distinct local population units that share a spawning ground providing recruits to different coastal fishery areas.     

西北太平洋柔鱼渔业生物经济模型及其管理策略

西北太平洋柔鱼是中国大陆、日本及中国台湾鱿钓船队共同开发的主要经济头足类之一,如何兼顾鱿钓船队的渔业利益,并综合考虑生态效益、经济效益和社会效益,科学制定渔业管理目标是确保柔鱼资源可持续利用的重要研究内容。根据中国大陆、日本及中国台湾鱿钓船队的渔获统计数据及相关经济参数,构建基于多船队的生物经济模型,模拟了50年内(1997—2047年)各捕捞船队开发柔鱼资源过程中的动态变化,并探讨了在10种不同的管理方案下各船队捕捞努力量、柔鱼资源量、渔获产量及其渔业利润随时间的动态变化。结果表明,在所有设计方案下,随着捕捞努力量的动态变化,资源量在前10a均呈急剧下降趋势,随后经长期波动后逐渐趋于稳定并维持在较低水平。从长期效益来看,方案9(提高中国台湾船队捕捞系数)的累计产量及累计利润中等,但能兼顾各国或地区船队间的经济利益和社会效益,可建议以方案9作为柔鱼渔业的参考管理目标;从柔鱼资源保护角度来看,方案4(提高中国大陆船队作业成本)的资源量保持最好,可以对方案4进行适当的优化作为参考管理目标,即提高中国大陆船队作业成本,同时适当降低日本船队的可捕系数,可确保柔鱼资源量保持在更高的水平上。     

Ecological Meltdown in the Firth of Clyde,Scotland: Two Centuries of Change in a Coastal Marine Ecosystem

Background

The Firth of Clyde is a large inlet of the sea that extends over 100 km into Scotland''s west coast.

Methods

We compiled detailed fisheries landings data for this area and combined them with historical accounts to build a picture of change due to fishing activity over the last 200 years.

Findings

In the early 19^th century, prior to the onset of industrial fishing, the Firth of Clyde supported diverse and productive fisheries for species such as herring (Clupea harengus, Clupeidae), cod (Gadus morhua, Gadidae), haddock (Melanogrammus aeglefinus, Gadidae), turbot (Psetta maxima, Scophthalmidae) and flounder (Platichthys flesus, Pleuronectidae). The 19^th century saw increased demand for fish, which encouraged more indiscriminate methods of fishing such as bottom trawling. During the 1880s, fish landings began to decline, and upon the recommendation of local fishers and scientists, the Firth of Clyde was closed to large trawling vessels in 1889. This closure remained in place until 1962 when bottom trawling for Norway lobster (Nephrops norvegicus, Nephropidae) was approved in areas more than three nautical miles from the coast. During the 1960s and 1970s, landings of bottomfish increased as trawling intensified. The trawl closure within three nautical miles of the coast was repealed in 1984 under pressure from the industry. Thereafter, bottomfish landings went into terminal decline, with all species collapsing to zero or near zero landings by the early 21^st century. Herring fisheries collapsed in the 1970s as more efficient mid-water trawls and fish finders were introduced, while a fishery for mid-water saithe (Pollachius virens, Gadidae) underwent a boom and bust shortly after discovery in the late 1960s. The only commercial fisheries that remain today are for Nephrops and scallops (Pecten maximus, Pectinidae).

Significance

The Firth of Clyde is a marine ecosystem nearing the endpoint of overfishing, a time when no species remain that are capable of sustaining commercial catches. The evidence suggests that trawl closures helped maintain productive fisheries through the mid-20^th century, and their reopening precipitated collapse of bottomfish stocks. We argue that continued intensive bottom trawling for Nephrops with fine mesh nets will prevent the recovery of other species. This once diverse and highly productive environment will only be restored if trawl closures or other protected areas are re-introduced. The Firth of Clyde represents at a small scale a process that is occurring ocean-wide today, and its experience serves as a warning to others.     

The feeding habits of six pelagic and predatory teleosts in eastern Cape coastal waters (South Africa)

A four-year study of the feeding habits of six pelagic teleost species in eastern Cape coastal waters of South Africa is analysed. These predators are Lichia amia, Pomatomus sallatrix, Seriola lalandi, Atractoscion aequidens, Katsuwonus pelamis and Thunnus albacares. All species occur in inshore coastal water (< 1 -8 km from shore) for at least part of the year. The tunas were also sampled from the edge of the continental shelf (40–50 km from shore). The use of squid 'beaks' and fish otoliths allowed accurate prey identification and size estimates. Variations in prey taken are attributed to differences in locality, predator species and size. Three pelagic fish species are important to all the predators: Sardinops ocettata, Etrumeus teres and Engraulis capensis. The inshore squid, Loligo reynaudi, is another major prey item. Offshore tuna samples revealed a different prey spectrum, viz. oceanic squid and saury, Scomberesox saurus, being taken frequently.     

Isotopic niche width differentiation between common bottlenose dolphin ecotypes and sperm whales in the Gulf of California

World populations or stock distinction of Tursiops truncatus has been difficult to assess, because of large variations in morphology, habitat, feeding habits, and social structure among areas, which may reflect phylogenetic segregation or ecological plasticity. In the Gulf of California, Mexico, two common bottlenose dolphin ecotypes (inshore and offshore) have been reported. The offshore ecotype is frequently observed in association with sperm whales (Physeter macrocephalus) but the reason for this is still unknown. To explore the degree of resource partitioning/overlap between these species and stocks, we used skin stable isotope values (δ¹³C, δ¹⁵N) to estimate quantitative metrics of isotopic niche width (Bayesian standard ellipse areas, SEA_B) and estimated their diet composition using Bayesian isotopic mixing models. The inshore ecotype in different regions (north, central, and south) of the Gulf of California exhibited distinct δ¹⁵N values and SEA_B, suggesting a latitudinal gradient in nitrogen sources of coastal localities. The SEA_B of inshore and offshore bottlenose dolphin ecotypes was completely distinct, indicating resource partitioning. Associated offshore ecotype and sperm whales had overlapping SEA_B. The isotopic mixing model indicates that a considerable proportion of both species’ diet is large Humbolt squid. Our results suggest that resource partitioning and species association are two strategies that bottlenose dolphin ecotypes use in this zone.     

Abundance and distribution of inshore fish in fished and protected areas in Lake Kariba,Zimbabwe

Abundance and size distribution of inshore fish populations was assessed by fishing with standard Lundgren survey gill-nets in areas open to fishing and reserved areas that are protected from fishing activities.The direct gradient analysis technique — Detrended Canonical Correspondence Analysis — revealed that fish abundance and their composition in Lake Kariba are strongly structured by lake morphometry.The comparison between fished and reserve areas showed that there was a significant reduction in mean length of commercially fished species in the fished areas and the size distribution curves were skewed, lacking small and large length classes. There was a higher abundance of non-commercial species in the fished areas. It was also revealed that the mochokid Synodontis zambezensis Peters 1852, was the most abundant species and was present at all depths sampled in all the stations.There were indications that non-commercial species were important in terms of abundance in the fished areas. These included S. zambezenzis, Schilbe intermedius (Ruppell, 1832) and other smaller species. This was attributed to them being selected against in the gill-nets.     

Spatiotemporal patterns of marine mammal distribution in coastal waters of Galicia, NW Spain

The spatial and seasonal distribution of cetaceans and possible links with environmental conditions were studied at the Galician continental shelf. Data were collected between February–August 2001 and June–September 2003 during opportunistic surveys onboard fishing boats. Seven species of cetaceans were identified from 250 sightings of 6,846 individuals. The common dolphin (Delphinus delphis) was by far the most frequently sighted and the most widely distributed species. Spatiotemporal trends in cetacean distribution and abundance, and their relationships with environmental parameters (sea depth, SST and chlorophyll-a) were quantified using generalised additive models (GAMs). Results for all cetaceans were essentially the same as for common dolphins alone. Modelling results indicated that the number of common dolphin sightings per unit effort was higher further south. The number of individual common dolphins seen per sighting of this species (i.e. group size) was however higher in the north and west of the study area, higher later in the year and higher in 2001 than in 2003. In contrast, the number of common dolphin calves seen (per sighting of this species) was higher in the south. Models including environmental variables indicated larger common dolphin group sizes in deeper waters and at higher chlorophyll concentrations (i.e. in more productive areas). There was also a positive relationship between survey effort and group size, which is probably an artefact of the tendency of the survey platforms (fishing boats) to spend most time in areas of high fish abundance. Numbers of common dolphin calves per sighting were found to be higher in shallower waters. The results are consistent with common dolphins foraging mainly in deeper waters of the Galician continental shelf, while more southern inshore waters may represent a nursery area.     

Comparing Trawl and Creel Fishing for Norway Lobster (Nephrops norvegicus): Biological and Economic Considerations

This study compares the fishing activity and landings of the trawl and creel fisheries for Norway lobster (Nephrops norvegicus (L.)) off the Portuguese coast, and evaluates the financial viability of two vessels typical of each fleet. Crustacean trawlers are part of an industrial fleet that, besides Nephrops, targets deep water shrimps. Creels are used by a multi-gear, multi-target artisanal fleet, fishing only in areas unavailable to trawlers and, when catching Nephrops, set specifically to target this species. Trawlers have in recent years contributed with 85% of the landings in weight, but only 74% in value (2005-2009 average). Despite smaller landings, the Nephrops creel fishery provides individuals of larger size and in better condition, thereby obtaining higher unit prices. Economic viability was also higher for the creel vessel, with trawling being only viable if major costs (such as labor and fuel) are covered by the revenue from other target species (e.g., the rose shrimp). At present, Nephrops populations on the South and SW coast are subject to intense fishing and to a recovery plan. The possibility of reallocation of some of the fishing effort directed at Nephrops from trawlers to creels is discussed in terms of the conservation of the resource and economic return.     

Combining Telephone Surveys and Fishing Catches Self-Report: The French Sea Bass Recreational Fishery Assessment

Fisheries statistics are known to be underestimated, since they are mainly based on information about commercial fisheries. However, various types of fishing activities exist and evaluating them is necessary for implementing effective management plans. This paper assesses the characteristics and catches of the French European sea bass recreational fishery along the Atlantic coasts, through the combination of large-scale telephone surveys and fishing diaries study. Our results demonstrated that half of the total catches (mainly small fish) were released at sea and that the mean length of a kept sea bass was 46.6 cm. We highlighted different patterns of fishing methods and type of gear used. Catches from boats were greater than from the shore, both in abundance and biomass, considering mean values per fishing trip as well as CPUE. Spearfishers caught the highest biomass of sea bass per fishing trip, but the fishing rod with lure was the most effective type of gear in terms of CPUE. Longlines had the highest CPUE value in abundance but not in biomass: they caught numerous but small sea bass. Handlines were less effective, catching few sea bass in both abundance and biomass. We estimated that the annual total recreational sea bass catches was 3,173 tonnes of which 2,345 tonnes were kept. Since the annual commercial catches landings were evaluated at 5,160 tonnes, recreational landings represent 30% of the total fishing catches on the Atlantic coasts of France. Using fishers'' self-reports was a valuable way to obtain new information on data-poor fisheries. Our results underline the importance of evaluating recreational fishing as a part of the total amount of fisheries catches. More studies are critically needed to assess overall fish resources caught in order to develop effective fishery management tools.     

The Species and Origin of Shark Fins in Taiwan’s Fishing Ports,Markets, and Customs Detention: A DNA Barcoding Analysis

The increasing consumption of shark products, along with the shark’s fishing vulnerabilities, has led to the decrease in certain shark populations. In this study we used a DNA barcoding method to identify the species of shark landings at fishing ports, shark fin products in retail stores, and shark fins detained by Taiwan customs. In total we identified 23, 24, and 14 species from 231 fishing landings, 316 fin products, and 113 detained shark fins, respectively. All the three sample sources were dominated by Prionace glauca, which accounted for more than 30% of the collected samples. Over 60% of the species identified in the fin products also appeared in the port landings, suggesting the domestic-dominance of shark fin products in Taiwan. However, international trade also contributes a certain proportion of the fin product markets, as four species identified from the shark fin products are not found in Taiwan’s waters, and some domestic-available species were also found in the customs-detained sample. In addition to the species identification, we also found geographical differentiation in the cox1 gene of the common thresher sharks (Alopias vulpinus), the pelagic thresher shark (A. pelagicus), the smooth hammerhead shark (Sphyrna zygaena), and the scalloped hammerhead shark (S. lewini). This result might allow fishing authorities to more effectively trace the origins as well as enforce the management and conservation of these sharks.     

The potential impacts of climate change on inshore squid: biology, ecology and fisheries

Squid are important components of many marine ecosystems from the poles to the equator, serving as both important predators and prey. Novel aspects of their growth and reproduction mean that they are likely to play an important role in the changing oceans due to climate change. Virtually every facet of squid life-history examined thus far has revealed an incredible capacity in this group for life-history plasticity. The extremely fast growth rates of individuals and rapid rates of turnover at the population level mean that squid can respond quickly to environmental or ecosystem change. Their ‘life-in-the-fast-lane’ life-style allows them to rapidly exploit ‘vacuums’ created in the ecosystem when predators or competitors are removed. In this way, they function as ‘weeds of the sea’. Elevated temperatures accelerate the life-histories of squid, increasing their growth rates and shortening their life-spans. At first glance, it would be logical to suggest that rising water temperatures associated with climate change (if food supply remains adequate) would be beneficial to inshore squid populations and fisheries—growth rates would increase, life spans would shorten and population turnover would accelerate. However, the response of inshore squid populations to climate change is likely to be extremely complex. The size of hatchlings emerging from the eggs becomes smaller as temperatures increase and hatchling size may have a critical influence on the size-at-age that may be achieved as adults and subsequently, population structure. The influence of higher temperatures on the egg and adult stages may thus be opposing forces on the life-history. The process of climate change will likely result in squids that hatch out smaller and earlier, undergo faster growth over shorter life-spans and mature younger and at a smaller size. Individual squid will require more food per unit body size, require more oxygen for faster metabolisms and have a reduced capacity to cope without food. It is therefore likely that biological, physiological and behavioural changes in squid due to climate change will have far reaching effects.     

Squid stock fluctuations and water temperature: temporal analysis of English Channel Loliginidae

1. Monthly series of abundance indexes for the English Channel squid stock, based on fishery statistics of the United Kingdom (1980–93) and France (1986–96), were compared with water temperature data. The two objectives of the study were to test empirical predictive models and to analyse the stock–environment relationship at various time scales; both correlation and time-series statistical techniques were applied. Sea surface temperature (SST) showed inter-annual fluctuations and month-to-month auto-correlation in addition to the annual cycle.
2. Trends in squid landings and temperature at the annual scale were found to be related, whatever the statistical method used (moving averages, cumulative functions or regression using averaged data).
3. Variable selection applied in a 'multi-month' model suggested that fishing season indexes could be predicted from temperatures observed in the previous winter. The link between mild winter conditions and cohort success in winter/spring spawning species suggested that early life survival (and/or growth) was involved. This empirical model is a first step in the development of environment-predicted recruitment indexes useful for management advice.
4. Seasonal decomposition was performed on both the squid resource data and SST data in search of short-term relationships. In spite of the flexibility of the loliginid life-cycle, no significant relationship was found between squid seasonally adjusted indexes and temperature anomalies in the previous months. This underlined the conclusion that temperature effect on cohort success was not constant throughout the year.