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.     

The exploitation of living resources in the Dutch Wadden Sea: a historical overview

An overview, based on written sources and personal observations, is presented of exploitation of living resources in and around the Dutch Wadden Sea during the past few centuries. It is concluded that before about 1900 exploitation was almost unrestricted. Exploitation of plants has been documented for saltmarshes and eelgrass beds. Fisheries have occurred for two species of hydroids, two species of polychaetes, one echinoderm species, at least seven species of molluscs, three species of crustaceans, and tens of species of fish. Hunting and egg collecting targeted almost all species of birds. Finally, two species of seals were exploited: information on exploitation of cetaceans is not available. Hence, it is likely that overexploitation may have been involved in the extirpation of several species. This supports an earlier suggestion that overexploitation played a part in the disappearance of at least 17 species from the Dutch Wadden Sea. This conclusion is confirmed by the observation that several extirpated species have returned after protective measures were introduced for the Dutch Wadden Sea area.     

Adenokarzinom in der Harnblase einer männlichen Fischkatze (Prionailurus viverrinus Benett, 1833)

A 12-year-old male fishing cat (Prionailurus viverrinus) was presented with apathia, haematuria and dysuria-stranguria. The clinical examination revealed a firm mass in the caudal abdomen. Blood- and urinanalysis were performed as well as X-rays and sonography, which showed a mass in the bladder and free fluid in the abdominal cavity. Subsequent laparotomy revealed a tumor protruding from the wall of the bladder and a small perforation. Furthermore, firm nodules in the stomach wall, omentum and ileosacral lymphnodes were detected. Due to the age of the cat and invasiveness of the tumor euthanasia was elected. The histopathological diagnosis was: invasive adenocarcinoma of the bladder, stomach, omentum and metastases in the ileosacral lymphnodes. In contrast to the rare bladder tumors in domestic cats, there are several reports on transitional cell tumors in fishing cats. But to the authors knowledge there are no reports on adenocarcinomas of the bladder.     

Assessing effects of fishing prohibition on Posidonia oceanica seagrass meadows in the Marine Natural Reserve of Cerbère-Banyuls

The potential of alleviated fishing pressure measures established at the Marine Natural Reserve of Cerbère-Banyuls to affect phenological characters of P. oceanica, the main canopy-forming seagrass, was studied. Our results show differences in some leaf parameters between meadows under fishing prohibition measures compared to those without. In addition shallow P. oceanica meadows inside MPAs had lower non-structural carbohydrate content, yet are able to maintain themselves and, moreover, with an increased density. On the other hand, sexual reproduction was reduced inside protected areas.     

The political culture of poaching: a case study from northern Greece

Poaching has deep social and cultural roots and its meanings are multi-layered. This article explores the meanings attached to the practice of illegal hunting and fishing around Lake Kerkini in northern Greece. Here poaching must be considered in the context of a disordered ecosystem, where the dominance of locally maligned fish and bird species results from economic and environmental policy designed to benefit distant farmers. We conclude that poaching cannot be understood only as an individual action, but as one where collective and personal identities are defended in the face of seemingly irrevocable economic and social decline. The discussion shows that poachers identify different kinds of poaching. Some of the most apparent forms of poaching, done by local inhabitants, may be less damaging than other commercially oriented forms, including by outsiders. Poaching is motivated through a complex mix of factors. Our data lead us to discuss two manifestations of poaching (a) poaching as a form of collective resistance; and (b) poaching as a violation of culturally valued types of human-nature interaction. Some people who admit undertaking what they perceive as least detrimental forms of poaching are antagonistic towards what they construe to be truly harmful forms. Such people appear willing to act and to support actions against types of poaching they agree to be threatening. This is a message with potential importance for environmental management strategy.     

Modelling Cooperation between fishermen with a Cellular automaton. A framework for fishing effort spatial dynamics

In many fisheries sharing information between vessels is an important characteristic of fishermen's behaviour rarely modelled or analyzed. A Cellular Automaton is designed in an attempt to understand circumstances that favour group formation. The simulated world is toroidal with a static fishing resource distributed in patches. Movement decisions are random in the case of fishermen in a local scale. After a certain time interval, sharing information is possible between fishermen in a dynamic Moore's neighbourhood of cells at a broader scale and movement to adjacent areas may occur according to a set of rules. The dynamic neighbourhood is a novel concept defined in this work within the framework of Cellular Automata. Decision making by each fisherman is a function of the influence other fishermen (neighbours) exert on them as well as on personal knowledge, to form an opinion of the areas (cells) quality, and take action consequently.     

A fourteen-year overview of the fish assemblages and yield of the two oldest Algarve artificial reefs (southern Portugal)

Artificial reefs have been deployed worldwide for the last three decades in response to problems concerning coastal resources, ecosystems and fisheries. In many countries they have became important elements of integrated fisheries management plans. In Portugal two artificial reef systems (ARSs) were deployed by the Portuguese Institute of Marine Research (IPIMAR) in 1990, in the southern coast (Algarve). They were located off Faro and Olhão, over different sea-bottom types and located at different distances from the coastline. To analyse the effect of ARSs deployment on local fish assemblages and to evaluate their effectiveness in terms of mean fishing yields and mean number of species caught, fishing surveys have been conducted over 14 years (256 net sets) using a gillnet to sample the ARS of Faro and Olhão and respective control sites. The fishing yields from the ARs continually exceeded those from the control sites, in both the mean number of species caught and the mean CPUE in weight (1.8–2.6 times); both were higher at Faro. Moreover, the comparison between fish assemblages from the ARS and respective control sites showed that the deployment of the man-made structures did not change the composition of the fish assemblages caught by the gill nets, or the equilibrium of the community, since the relative proportion of the different functional groups of fish remained stable. The ARSs are a useful management tool on the Algarve coast, enhancing and diversifying the catches, thus contributing to improved local artisanal fisheries, which play a major role in this region.     

Habitat correlates of the distribution and biomass of Seychelles' reef fishes

Synopsis Relationships between quantitative measures of habitat type and the biomass of Chaetodon, Scarus and Parupeneus species were investigated across 35 reef sites in the Inner Seychelles Group. Multiple regression was used to determine the proportion of variance in biomass between sites which could be explained by depth, exposure, vertical relief, topographic complexity, live coral cover, coral rubble cover, rock cover, sand cover, underlying carbonate substrate, underlying sand substrate, underlying rock substrate and an index of fishing intensity. A significant proportion of the variance in biomass was explained by habitat variables and the index of fishing intensity for 7 of 12 Chaetodon species (23–52% of variance explained), 3 of 6 Parupeneus species (33–40%), and 10 of 13 Scarus species (14–46%). Within genera, different groups of habitat variables explained the variance in biomass for different species and, of the variables studied, only the proportion of underlying sand substrate failed to explain a significant proportion of the variance in biomass for any species. Quantitative relationships between the biomass of Chaetodon and habitat were often in accordance with those suggested by previous studies of their ecology, life-history and distribution at other Indo-Pacific locations. However, the habitat associations of the Parupeneus and some Scarus species have not been studied at other locations and clearly warrant further investigation. It was concluded that habitat was an important determinant of the distribution of many Seychelles reef fishes, but that the habitat variables examined were rarely the most important determinant of biomass. However, the inclusion of a procedure to collect habitat data provided a useful means by which to reduce the unexplained variance associated with visual census biomass estimates and therefore improves the possibility of elucidating the effects of other factors on the biomass of Seychelles reef fishes.     

Combining ecology,human demands,and philosophy into the management of northern pike in Michigan

Northern pike (Esox lucius Linnaeus) are a common sportfish native to most waters in Michigan. Early use of northern pike was unregulated consumptive harvest. Pike anglers today vary from those interested in intense harvest, to winter spear fisheries, to those interested in catching trophy fish. Michigan pike are now managed within three ecological groupings: 1. High density and slow growing populations, managed to increase harvest and reduce density (managed with a daily bag limit of 5 fish and no size limit). 2. Moderate density populations with normal growth (most populations, managed with a 61-cm (24-in) size limit and creel of 2 fish per day). 3. Low density and rapid growing populations (managed for trophy fisheries with a 76-cm (30-in) size limit and restricted take). Recent management challenges also include loss of wetland-spawning habitat, driving a need for stocking to supplement natural reproduction. Michigan has managed spawning marshes and other habitat to produce northern pike from natural waters, and recent demand has led to hatchery production of fry. Technology for hatchery production has moved from extensively growing pike and stocking at a small size to the current system using pelleted feed, growing fish to a larger size at a lower density. Future plans for pike management in Michigan are even more focused on using ecology as a means to manage lakes and streams, but will require much more research to be feasible. Guest editors: J. M. Farrell, C. Skov, M. Mingelbier, T. Margenau & J. E. Cooper International Pike Symposium: Merging Knowledge of Ecology, Biology, and Management for a Circumpolar Species