Modelling fish trade liberalisation: Does fish trade liberalisation result in welfare gains or losses?

Recent research has on the basis of general equilibrium models warned that trade liberalisation in non-optimally managed renewable resources might cause over-exploitation and reduced steady-state welfare. Welfare effects of trade liberalisation in open access and optimal management are found case specific and dependent on factors such as the country's status as importer or exporter, the state of the fish stocks and the size of the countries on the world market. The present paper develops an alternative partial equilibrium framework capable of identifying welfare effects of fish trade liberalisation also in the presence of complex but realistic management schemes, such as regulated open access and regulated restricted access. The case dependency known from the general equilibrium analysis is confirmed, but the introduction of realistic fisheries management schemes in the partial equilibrium model extended this case dependency. The welfare effect of trade liberalisation in an exporter country is negative under open access, but was found positive under regulated restricted access in the present paper.     

Estimating population parameters in an ‘open’ fish population

A model for an ‘open’ fish population is described. Basically an expansion of the classical catch equation, it includes a ‘population change’ coefficient to allow for changes in population size induced by causes other than fishing. The model relates this coefficient to catch, fishing effort, initial population size, and catchability coefficient. With observed catch and fishing effort data incorporated, the remaining parameters are estimated by minimising sums of squares. This estimation process is applied to data from both real and simulated fisheries, and is shown to be effective if the basic assumptions of the model are met. If this is not so considerable errors occur, and these are investigated with respect to the examples.     

Predatory fish and their prey — an overview of trophic interactions in the fish communities of the west and south coasts of South Africa

Fish communities over continental shelves are of three types: pelagic, rocky reef and soft substrata. The pelagic community of the South African west coast is dominated by clupeiform fish, which are the principal prey of snoek, the dominant piscivorous teleost in the area, and other fish, including tuna and pelagic sharks. Keystone prey species are broadly similar on the South African south and west coasts, but predator composition differs. Studies of rocky reef fish suggest that the fauna of the South Coast is more diverse than that of the West, the West Coast having fewer species and only two reef fish species being taken in linefisheries. Feeding interactions of some of the dominant species have been established, but the status of commercially less important fish such as elasmobranchs and small species is poorly known. The community and feeding interactions of fish living over soft substrata are better known and part of this fauna is taken by demersal trawlers. The two species of Cape hake dominate the communities on both coasts, but the fauna is more diverse on the Cape south coast. Generally, much of the present ichthyological knowledge is derived from the ecologically narrow perspective of commercial fisheries. Nevertheless, the patterns of diversity appear to conform to previous work, which has indicated a lower species diversity in the Atlantic than in the Indian Ocean. Knowledge of commercially unimportant fish is fragmentary, and understanding of the ecological interactions on the South Coast generally lags that of the West.     

Have there been recent changes in climate? Ask the fish

It is generally accepted that a climate shift occurred about 1977 that affected the dynamics of North Pacific marine ecosystems. Agreement on the possibility of further climate shifts in 1989 and the late 1990s is yet to be achieved. However, there have been changes in the dynamics of key commercial fishes that indicate changes in their environment occurred in the early 1990s, and possibly around 1998. One method of measuring climate change is to observe the dynamics of species that could be affected.Several studies have described decadal-scale changes in North Pacific climate–ocean conditions. Generally, these studies focus on a single index. Using principal components analysis, we use a composite index based on three aspects of climate ocean conditions: the Aleutian Low Pressure Index, the Pacific Atmospheric Circulation Index and the Pacific Interdecadal Oscillation Index. We link this composite index (Atmospheric Forcing Index) to decadal-scale changes in British Columbia salmon and other fish populations. Around 1989 there was a change from intense Aleutian Lows (above average south-westerly and westerly circulation patterns and warming of coastal sea surface temperatures) to average Aleutian Lows (less frequent south-westerly and westerly circulation and slightly cooler coastal sea surface temperatures in winter). These climate–ocean changes were associated with changes in the abundance and ocean survival of salmon (Oncorhynchus spp.), distribution and spawning behaviour of hake (Merluccius productus) and sardines (Sardinops sagax) and in recruitment patterns of several groundfish species.     

The requirement to rebuild US fish stocks: Is it working?

The Magnuson–Stevens Fishery Conservation and Management Act (MSA) was amended in 1996 to require that overfished stocks be rebuilt in as short a time period as possible, not to exceed 10 years, with limited exceptions. This comment examines the basic but important question of whether the implementation of rebuilding plans under the 1996 amendments has in fact been associated with biomass recovery. Specifically, for each of the 44 stocks examined, this analysis compares the biomass trend before rebuilding plan implementation to the trend after rebuilding plan implementation using a linear trend-break model. The analysis demonstrates a statistically significant positive association between the implementation of rebuilding plans and standardized biomass in 19 of 44 stocks. None of the 44 stocks examined showed a statistically significant negative association. The analysis showed a strong temporal relationship between the implementation of the policy and rebounds in fish stocks.     

Can the United States have its fish and eat it too?

As domestic affluence increases, nations advocate for conservation policies to protect domestic biodiversity that often curtail natural resource production activities such as fishing. If concomitant consumption patterns remain unchanged, environmentally conscious nations with high consumption rates such as the U.S. may only be distancing themselves from the negative environmental impacts associated with consuming resources and commodities produced elsewhere. This unintended displacement of ecosystem impacts, or leakage, associated with conservation policies has not been studied extensively in marine fisheries. This paper examines this topic, drawing on case studies to illustrate the ways in which unilateral marine conservation actions can shift ecosystem impacts elsewhere, as has been documented in land use interventions. The authors argue that the U.S. should recognize these distant ecological consequences and move toward greater self-sufficiency to protect its seafood security and minimize leakage as well as undertake efforts to reduce ecosystem impacts of foreign fisheries on which it relies. Six solutions are suggested for broadening the marine conservation and seafood consumption discussion to address leakage induced by U.S. policy.     

Do agonistic behaviours bias baited remote underwater video surveys of fish?

Marine environments require monitoring to determine the effects of impacts such as climate change, coastal development and pollution and also to assess the effectiveness of conservation measures. Marine protected areas (MPAs) are being established globally and require periodic monitoring to determine whether their objectives are being met. Baited underwater video systems are becoming a popular method for monitoring change within protected fish populations, because they are less damaging to habitats than bottom trawling and allow for more statistical powerful comparisons to determine spatial and temporal patterns in the relative abundances, lengths and biomass of demersal and pelagic fishes. However, much remains uncertain about how interactions between the fish and bait and between the fish themselves affect the results obtained. Agonistic behaviours are frequently observed around the bait of the camera and potentially bias fish density estimates by altering the number and size classes seen at cameras. Here we counted the number of agonistic behaviours between pink snappers (Pagrus auratus), the size of fish involved and whether the fish left the field of view following such behaviours. The study consisted of 20 baited underwater video deployments inside a New Zealand marine reserve and 20 in adjacent open areas. We observed a significant relationship between the peak number of fish observed at the camera and the total number of agonistic behaviours, as well as the number of both aggressor and subordinate fish leaving the camera field of view following interactions. The slope of the latter relationship and thus the absolute numbers of fish leaving were higher for subordinate fish. As subordinates were significantly smaller than aggressors, the apparent size frequency distribution is likely skewed away from smaller size classes. The staying time of the fish and thus the maximum number of fish present at the camera will be reduced by agonistic behaviours and the absolute magnitude of this effect appears to be greater at high fish densities. Our results suggest that an overall effect of these phenomena is to underestimate the differences in abundance between MPAs and open areas, but also to overestimate differences in average size.     

Do Mediterranean fish assemblages associated with marine caves and rocky cliffs differ?

Fish assemblages associated with marine caves and rocky cliffs were investigated in the Salento Peninsula (SE Italy, Mediterranean Sea) by using visual census methods. Sampling was done at three sites, each of which included 4 habitat types: the external and the internal portions of caves, and shallow and deep rocky cliffs. 10 and 13 species were found exclusively inside cave habitats (e.g. Corcyrogobius lichtensteini, Thorogobius ephippiatus and Grammonus ater) or in rocky cliffs (e.g. Diplodus annularis, Sarpa salpa, Sparisoma cretense, Spondyliosoma cantharus), respectively. The four habitat types shared 10 species, and the external portions of the caves shared the most species (both with the internal cave portions and the external rocky cliffs). As a general rule, dissimilarity in the fish assemblage structure between habitats was far greater than dissimilarity between sites. Apogon imberbis (mostly associated with caves) and Chromis chromis (typifying rocky cliffs, mainly the deep ones) mostly contributed to dissimilarities between caves and rocky cliffs. Apogon imberbis (mostly associated with internal caves) and Coris julis (mainly associated to external cave portions) contributed strongly to dissimilarities between internal and external cave portions, while C. chromis, Symphodus mediterraneus and C. julis (associated with the deeper cliffs) and Thalassoma pavo (mostly present in shallow cliffs) differentiated deep and shallow cliffs. Diplodus vulgaris, Oblada melanura and Mullus surmuletus showed a marked increase in density during the cold season in the caves. These results show that fish assemblages associated with rocky reefs rich in marine caves (in terms of relative densities, species composition, species richness, exclusive species and presence of juveniles of some valuable species) may be affected by the peculiar ecological conditions within caves, which could provide additional resources for fishes (e.g. food availability, refuge against predators, sand patches within a rocky matrix) compared to rocky reefs without caves. These results suggest that stretches of rocky coasts rich in marine caves should be considered within management/conservation programs (e.g. when establishing Marine Protected Areas).     

An estimate of fish biomass at the bottom layer of the Bohai Sea

The biomasses of fishes at the bottom layer of the Bohai Sea are extimated by analysing the data on samples (447 hauls,more than 0.2 million in number or 20 t in weight of fishes) collected monthly by our institute from April, 1982 to May, 1983 by a pair of bottom trawls through the Bohai Sea. The exploitation problems are also discussed in this paper.     

Relationship between deep-sea fish distributions and oceanic conditions of the East China Sea

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SoFISHticated policy – social perspectives on the fish conflict in the Northeast Atlantic

Ecosystem changes currently question the traditional allocation of fishing rights and quotas in the fishery of Northeast Atlantic mackerel and Norwegian spring-spawning herring in the Northeast Atlantic. Variability in the distribution of these highly migratory species escalated in a political conflict between member states of the European Union, Iceland, the Faroe Islands and Norway, which is a driving force for unsustainable fishery. The aim of this paper is to investigate this conflict by outlining the social understandings of diverse stakeholders by using the Q methodology. The method reduced the complexity of numerous opinions, detected four distinct perspectives and simultaneously categorised the participating stakeholders. Although the perspectives differ in various elements, the protection of economic interests seems to dominate over the quest for sustainability. The call of all stakeholders in this study to clarify the fishing rights in the Northeast Atlantic reveals a clear deficiency of the current international fishery management in handling abrupt ecological changes and the necessity to acknowledge this as a complex adaptive system.     

Estuarine production of resident and nursery fish species: Conditioning by drought events?

The production of resident (Pomatoschistus minutus and Pomatoschistus microps) and marine juvenile fish species using the Mondego estuary (central Portugal) as nursery grounds (Dicentrarchus labrax, Platichthys flesus, Solea solea), was assessed in order to: (1) understand the potential of the estuary for fish production; (2) know the production of nursery fish species likely to be exported to the coastal stocks; and (3) how anthropogenic and natural stress could influence the estimated production. Sampling occurred from June 2003 to May 2006 and together the 5 species in study comprised around 70% of the whole fish community numbers and biomass. Increasing drought conditions were observed, starting with a normal hydrological year in 2003 until attaining a severe drought in 2005, which resulted in low river discharges (1/3 of the mean river discharges in 2003). Additionally, high water temperatures were observed in 2003 and 2005 (24 and 26 °C, night temperatures). The secondary production was estimated using the increment summation method, after recognition of the cohorts. Production was in general lower in the Mondego estuary when compared to other systems, which was associated to the estuary's small area (only 3.4 km², less than 1/4 of area compared to other studied systems). Dicentrarchus labrax was among the most productive species. Production decreased in the drought year for all species, especially evident for D. labrax, P. minutus and P. flesus. No direct effects could be attributable to the salinity and temperature variations and to the low freshwater discharges (resulting from the drought and high temperatures), yet these were pointed as probable major reasons for the decreased production. A significant reduction (15–45% reduction in the estuarine production) was also concluded for the potential production to be exported for coastal areas by the nursery species in the drought conditions.     

Market-oriented regional fisheries management—an analysis of four fish regions in the North Atlantic

What influence do exchange methods have on ex-vessel prices and what are the potential implications for the regional management of the fisheries? This paper undertakes an empirical analysis of exchange methods and ex-vessel prices for specific demersal fish controlled for fish size and quantity in four North Atlantic regions, including Iceland, North-Norway and Scotland. The methodology consists of a comparative analysis of total average price (TAP) and Anova analysis of monthly average prices of cod and plaice landed fresh during the period 1990–1999. Scotland's auctions have the highest TAPs for the species analysed whilst the lowest TAPs are returned from contract sales in Iceland and North-Norway. Icelandic auctions and Møre–Romsdal auctions adopt intermediate positions in this price hierarchy. Price differences are still present even when correcting for factors such as legal barriers, transport costs from different geographical locations, exchange fees and seasonal variations in supplies. The implications of these findings for current and prospective systems of regional resource and coastal management are then considered and the scope and need for further study is established.     

Do environmental factors influence the movement of estuarine fish? A case study using acoustic telemetry

Telemetry methods were used to investigate the influence of selected environmental variables on the position and movement of an estuarine-dependent haemulid, the spotted grunter Pomadasys commersonnii (Lacepède 1801), in the Great Fish Estuary, South Africa. Forty individuals (263–698 mm TL) were surgically implanted with acoustic coded transmitters and manually tracked during two periods (7 February to 24 March 2003; n = 20 and 29 September to 15 November 2003; n = 20). Real-time data revealed that spotted grunter are euryhaline (0–37) and are able to tolerate large variations in turbidity (4–356 FTU) and temperature (16–30 °C). However, the fish altered their position in response to large fluctuations in salinity, temperature and turbidity, which are characteristic of tidal estuarine environments. Furthermore, tidal phase had a strong influence on the position of spotted grunter in the estuary.     

Theory and practice of why auctions differ—a study of two fish auctions in Norway

In this paper we will study two auctions for fish found in Norway, and compare them applying auction theoretical assumptions. We will use the Revenue Equivalence Theorem (RET) as a basis to explain why these two different auction mechanisms are chosen for the sale of fish. It is shown that the issues of risk aversion, common values and inclusion of travel costs may explain the choice of auction institution.     

Aquaculture and the poor-Is the culture of high-value fish a viable livelihood option for the poor?

This study evaluates the role of high-value fish culture in the livelihoods of coastal households in southern Thailand. The study shows that grouper culture, promoted as an alternative to destructive fishing practices, can make a substantial contribution to household incomes. However, fishing and aquaculture play contrasting roles in the livelihoods of coastal fishers and should be considered as complementary rather than alternative occupations. The study found that poorer households can benefit significantly from raising grouper in cages if certain conditions are met, including access to credit and the substitution of financial for natural capital.     

Occurrence of gravel in the stomachs of two New Zealand stream‐dwelling fish (note)

Gravel occurred in. the stomachs of 17.8% of 924 Galaxias vulgaris and 2.8% of 430 Philypnodon breviceps taken from the Glentui River, Canterbury, between June 1970 and November 1971. It is suggested that differences in feeding habits and feeding locality are responsible for the difference in occurrence of gravel in the stomachs of the two fish species. Galaxias vulgaris feeds in the water column in riffles and, being a drift feeder, is more likely to ingest inedible material by accident than is P. breviceps, which feeds on the bottom in sheltered or quiet stretches of the river.     

Are assemblages of the fireworm Hermodice carunculata enhanced in sediments beneath offshore fish cages?

Abundances of the fireworm Hermodice carunculata were counted through a monitoring assessment study of fish cages in Barranco Hondo（NE Tenerife）. Seven campaigns were conducted from November 2007 to June 2010 and temporal variations were found, as well as differences among sampling stations. The polychaete H. carunculata obtained its highest abundance in sediments beneath fish cages throughout the study period. Thus, the assemblages of this omnivorous species were favoured by the presence of fish cages.     

Do predatory fish of benthic crustaceans vary between kelp and barren reef habitats in northeastern New Zealand?

Fish assemblages that included known predators of benthic crustaceans were compared between kelp and barren habitats in northeastern New Zealand using baited underwater video census methods. The benthic-feeding fish were observed in winter, spring/summer and autumn, as well as during night-time in spring/summer. Overall, the fish assemblages varied between barren and kelp habitat, being most marked in winter. Individual benthic-feeding species, such as grey mao mao (Scorpis lineolatus) and leatherjacket (Meuschenia scaber) were associated with barren habitat, while the spotted wrasse (Notolabrus celidotus) was more strongly associated with kelp habitat. The results suggest that changes in habitats on coastal reefs affect populations of species that are benthic predators, which may in turn influence the distribution and abundance of their prey species, such as juvenile spiny lobsters.