Changes in life history and ecological characteristics of coral reef fish catch composition with increasing fishery management

Abstract Length, life history and ecological characteristics of landed fish communities were studied over a 10‐year period to test theories of fishing disturbance during a time of increased gear and closure management in heavily utilised fisheries. It was predicted that with greater management restrictions: (1) the earliest and fastest responses in the fishery will be seen in those species with faster turnovers, or relatively lower vulnerabilities to fishing; (2) the fishery would transition to a landed catch with higher mean trophic levels, and greater mean body lengths. In addition, the removal of a non‐selective, small‐mesh seine nets should benefit the catch of gears that previously had the greatest species selectivity overlap with the seine net. Many predictions were supported, although maximum lengths and lengths at maturity responded more rapidly than anticipated. The response to eliminating the non‐selective seine net was a more rapid increase in sizes caught by gears with a larger overlap in size (hook and lines) than species selectivity (gill nets). The simultaneous comparison of management systems over time indicates that open‐access fishing grounds can benefit from restrictions imposed in adjacent fishing grounds. The study indicated that multi‐species coral reef fisheries management objectives of maximising yields, as well as maintaining the fish community’s life‐history diversity, require management trade‐offs that balance local socio‐economic and biodiversity needs.     

Phenotypic plasticity for life history traits in a stream population of the threespine stickleback, Gasterosteus aculeatus L.

Abstract – The life history traits of breeding size, clutch size, egg size and relative clutch mass were examined for evidence of plasticity within a set of six annual samples of threespine stickleback, Gasterosteus aculeatus L., females from south-central Alaska, USA. Three samples (from 1992, 1996 and 1999) were of stickleback native to, and living within, a stream environment, while three (from 1995, 1996 and 1999) represented fish living within a pond environment recently colonized by the stream stickleback. Significant differences between stream and pond fish were found for all four traits. For most traits, pond-living females showed greater variation both across and within years than did stream-living females. Although extremely rapid evolution within the pond, or genetic drift caused by low founding population size, could not be completely ruled out, trait changes across years in both environments were interpreted as representing adaptive plasticity.     

Varying the timing of oyster transplant: implications for management from simulation studies

The transplanting of oysters from one ground to another is a common practice in the oyster industry. In Delaware Bay, for instance, oysters are typically transplanted from upper-bay low-salinity seed beds onto lower-bay leased grounds for growth and conditioning before market. The higher salinity on the leased grounds, however, also favours higher losses to predation and disease. A coupled oyster–Perkinsus marinus–predator model was used to investigate how varying the timing of transplant affects the ultimate yield of Eastern oysters, Crassostrea virginica, in Delaware Bay. Simulations were run in which oysters were moved from seed beds to leased grounds in November, January, March, April and May. The number of market-size (≥ 76 mm) adults available for harvest in the following July to November was compared for populations undergoing mortality from predation (crabs, oyster drills) and/or disease (Perkinsus marinus). In all simulations, the abundance of market-size oysters declined between July and November. However, transplanting oysters in November resulted in the largest yield of market-size oysters for all harvest times; transplanting in May resulted in the smallest yield. The autumn transplant allows oysters to benefit from the larger spring phytoplankton bloom over the leased grounds in the lower estuary. The effect of varying the season of transplant was most noticeable if oysters were harvested early (July or August). In all simulations, transplanting resulted in a higher abundance of market-size oysters than direct harvest from the seed beds. Direct harvest would rarely be advantageous if the cost of transplant were insignificant and the relative rates of mortality were as stipulated. However, a May transplant is only moderately better than a direct harvest and the economic benefits of either option are likely to be determined by the cost of transplanting and the mortality associated with the process. In the same vein, the decision as to when to harvest relies on balancing the increased price obtained for oysters in the autumn with the increased loss owing to predation and disease. Awaiting an autumn harvest is clearly much riskier if the principal source of mortality is disease rather than predation, because disease mortality is concentrated on the market-size oysters and is greatest in the autumn.     

The life history of Tenualosa macrura in Sarawak, further notes on protandry in the genus and management strategies

Abstract  The contraction of Tenualosa macrura (Bleeker) to the Sarawak coast and a small part of Sumatra, and the decline in its fishery mirror what has happened to three other species in the genus. Little was known of this species in its last stronghold in Sarawak where it is important for management and conservation reasons to understand its biology and life history. It forms part of a multispecies fishery where effort is uniform, but catches follow a lunar cycle. Tenualosa macrura is protandrous, but low numbers of small females suggest diandry. In Sumatra Tenualosa macrura spawn throughout the year, but in Sarawak have a seasonal peak in the NE monsoon (December). This has management implications because the Sarawak fishery ceases at this time because of adverse weather, hence reducing fishing pressure on spawning T. macrura . Management measures introduced in Sarawak for Tenualosa toli (Valenciennes) may therefore not be required for T. macrura .     

Searching for sensitivity in the life history of Atlantic menhaden: inferences from a matrix model

We used modified Leslie matrix models to explore the life history of Atlantic menhaden ( Brevoortia tyrannus ). By examining the sensitivity of long-term population growth rates to changes in vital rates, we identified those life history components which can cause large population level responses. Our models subdivide the first year of life into five stages (eggs, early larvae, late larvae, juveniles, and 'peanuts' or subadults), and population growth rate responds most strongly to changes in juvenile and late larval stages. The relative ranking between these stages is dependent on the magnitude of mortality during the prejuvenile stages relative to juvenile mortality. An examination of low-level model parameters indicates that the population growth rate is influenced by the growth and mortality rates during the time when young-of-the-year menhaden are gaining access to and residing in the estuaries. Sensitivity to changes in many adult metrics, such as fishing mortality, were relatively low. We conclude that a better understanding of biotic and abiotic factors that influence the late larval and juvenile stages will further our understanding of population dynamics in this species.     

Linking the biology and ecology of key herbivorous unicornfish to fisheries management in the Pacific

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Interlocked use of inland fish resources: a new management strategy under private property rights

Abstract  Interlocked use of multiple inland vendace, Coregonus albula (L.), stocks is a relatively new strategy to exploit asynchronous fluctuations in abundance of natural fish stocks between waterbodies. It combines vendace stocks from different lakes or parts of lakes into one interlocked stock to be managed across waterbody ownership boundaries. Management of interlocked stocks can be regarded as one form of portfolio management. Exploitation of interlocked stocks should reduce the interannual variation in yield, and thus ensuring fishers more constant income and the market more constant material flow. The strategy requires fishers to increase their mobility, to benefit from asynchronous fluctuations in abundance of vendace stocks between exploitable waters. A postal inquire addressed to Finnish commercial inland fishers examined whether existing property rights institutions' and fishers' harvesting policies were appropriate to establish interlocked use of multiple vendace stocks. Almost half of fishers had, to some extent, reaped benefit from a fishing strategy that included small-scale mobility, which is consistent with the proposed strategy. By harvesting three or four lakes and stocks, fishers increased their yield compared with exploiting one fishing ground and one vendace stock. Public ownership provided fishers access to stocks nearer their place of residence than other ownership types.     

Evolutionary assembly rules for fish life histories

We revisit the empirical equation of Gislason et al. (2010, Fish and Fisheries 11 :149–158) for predicting natural mortality (M, year^?1) of marine fish. We show it to be equivalent to , where L_∞ (cm) and K (year^?1) are the von Bertalanffy growth equation (VBGE) parameters, and L (cm) is fish length along the growth trajectory within the species. We then interpret K in terms of the VBGE in mass , and show that the previous equation is itself equivalent to a ?? power function rule between M and the mass at first reproduction (W_α); this new ?? power function emerges directly from the life history that maximizes Darwinian fitness in non‐growing populations. We merge this M, W_α power function with other power functions to produce general across‐species scaling rules for yearly reproductive allocation, reproductive effort and age at first reproduction in fish. We then suggest a new way to classify habitats (or lifestyles) as to the life histories they should contain, and we contrast our scheme with the widely used Winemiller–Rose fish lifestyle classification.     

Status and management of fish populations of Rawal Dam reservoir, Pakistan

Abstract Studies were conducted to determine the composition and relative abundance of commercially desirable and less desirable fish populations of Rawal Dam reservoir. Fifteen fish species belonging to 11 genera were identified. The less desirable species were abundant, constituting 62.3%, 84.8% and 78% of the total number of fish sampled on three occasions. Carnivores were represented by two species with very low percentage composition by number or weight. The ratio of total weight of forage fish to that of carnivorous fish indicated an unbalanced population in the lake. The proportion of the fish population at harvestable size suggests a balanced population, but this index may have been overestimated because of a minimum harvestable size.     

Optimising harvest strategies in a multi‐species bivalve fishery

Abstract Optimising harvests from fishery resources requires appropriate data. In this study, fishery‐independent survey and size‐at‐first maturity (L₅₀) data were used to assess the suitability of current minimum legal sizes (MLS) and total allowable commercial catches (TACC) in the South Australian, mixed‐species, mud‐cockle (Katelysia spp.) fishery. Estimates of L₅₀ suggested the MLS was conservative in one fishing zone (Coffin Bay), but appropriate elsewhere. Harvestable‐biomass estimates (HB) demonstrated that TACCs were excessive in the Port River (41% of HB), suitable in Coffin Bay (10% of HB) and precautionary in the West Coast (1.5% of HB) fishing zones. Consequently, the MLS was decreased by 5 mm shell length in Coffin Bay and the TACCs for the Port River (reduced by 80%) and West Coast (increased by 40%) amended. This study demonstrated that harvest strategies in mixed‐species fisheries can be optimised by explicitly considering data on species composition, abundance and population biology.     

刺激隐核虫生活史的观察

通过对刺激隐核虫的取样,在湿房中24℃下培养,在显微镜下连续观察其生长发育情况。其结果为离开鱼体的刺激隐核虫营养体约经8～10h发育成包囊,包囊壁厚;4～6d包囊内出现窜动的纤毛幼虫;5～8d纤毛幼虫冲撞包囊壁,出现一孔洞,由这一孔洞进入水体中;约5～9d完成营养体→包囊→纤毛幼虫的过程;整个生活史周期为8～13d。     

Using accessible watershed size to predict management parameters for Chinook salmon, Oncorhynchus tshawytscha, populations with little or no spawner-recruit data: a Bayesian hierarchical modelling approach

Abstract  Escapement goals for Chinook salmon, Oncorhynchus tshawytscha (Walbaum), populations tend to be highly uncertain due to variability in, and in some cases complete absence of, spawner-recruit data. A previous study of 25 populations from Oregon to Alaska demonstrated that watershed size is a good predictor of unfished equilibrium population size. Here this relationship is further developed by evaluating a series of Bayesian hierarchical models of increasing complexity. The model that performed best included a temporal random walk to account for patterns in the spawner-recruit residuals and life history-specific distributions for the productivity parameter.     

Metapopulations and salmonids: a synthesis of life history patterns and empirical observations

Abstract – Metapopulation theory has attracted considerable interest with reference to the salmonids. There has been little empirical evidence, however, to guide the evaluation or application of metapopulation concepts. From knowledge of salmonid life histories and our own work with bull trout ( Salvelinus confluentus ), Lahontan cutthroat trout ( Oncorhynchus clarki henshawi ) and westslope cutthroat trout ( Oncorhynchus clarki lewisi ), we suggest that simple generalizations of salmonid metapopulations are inappropriate. Although spatial structuring and dispersal mechanisms are evident, the relevance of extinction and colonization processes are likely to vary with life history, species, scale, and landscape. Understanding dispersal, the role of suitable but unoccupied habitats, and the potential for extinction debts in non-equilibrium metapopulations are key issues. With regard to conservation of salmonids, we suggest that efforts to understand and conserve key processes likely to influence the persistence of populations or metapopulations will be more successful than efforts to design minimal habitat reserves based on metapopulation theory. ^NOTE     

The behavioural dynamics of fishers: management implications

In pursuing their livelihood, fishers develop strategies when faced with changes in regulations and other fishery conditions. Changes involve each individual in a decision‐making process governed by his/her own goals or constraints. Despite this reality, the complex dynamics of fishing has usually been ignored in designing management initiatives, which has contributed to management failures in many parts of the world. Fishers have generally been treated as fixed elements, with no consideration of individual attitudes based on their operating scales (geographical, ecological, social and economic) and personal goals. We review existing research on the social, economic and behavioural dynamics of fishing to provide insight into fisher behaviour and its implications for fisheries management. Emphasis is placed on fisher perception, and how fishers develop dynamic fishing tactics and strategies as an adaptive response to changes in resource abundance, environmental conditions and market or regulatory constraints. We conclude that knowledge of these dynamics is essential for effective management, and we discuss how such information can be collected, analysed and integrated into fisheries assessment and management. Particular emphasis is placed on small‐scale fisheries, but some examples from industrial fleets are provided to highlight similar issues in different types of fisheries.     

Early life history and recruitment of black crappie (Pomoxis nigromaculatus) in two South Dakota waters

Abstract— We compared the early life history of black crappie ( Pomoxis nigromaculatus ) in Richmond (an impoundment) and Brant (a natural lake) lakes during 1994-1996. We expected variable recruitment (i. e., missing year classes) in the natural lake and more consistent recruitment in the impoundment. Larval black crappie abundance was always higher in Richmond Lake than Brant Lake. Peak abundance of larval black crappie was highest during 1994 in both waters. However, peak larval abundance did not correspond with fall trap-net catch per unit effort (CPUE) of age-0 black crappie, which was highest during 1995. Thus, recruitment of black crappie was not simply a function of the number of larvae hatched. Similar trends in catches of age-0 black crappie with the ichthyoplankton trawl and trap nets for both water bodies during 1994-1996 suggest that broad environmental factors similarly affected reproduction and recruitment in Richmond and Brant lakes.     

Pan‐continental invasion of Pseudorasbora parva: towards a better understanding of freshwater fish invasions

In recent years, policy‐makers have sought the development of appropriate tools to prevent and manage introductions of invasive species. However, these tools are not well suited for introductions of non‐target species that are unknowingly released alongside intentionally‐introduced species. The most compelling example of such invasion is arguably the topmouth gudgeon Pseudorasbora parva, a small cyprinid species originating from East Asia. A combination of sociological, economical and biological factors has fuelled their rapid invasion since the 1960s; 32 countries (from Central Asia to North Africa) have been invaded in less than 50 years. Based on a combination of monitoring surveys (2535 populations sampled) and literature reviews, this paper aims to quantify and characterise important invasion parameters, such as pathways of introduction, time between introduction and detection, lag phase and plasticity of life history traits. Every decade, five new countries have reported P. parva introduction, mainly resulting from the movement of Chinese carps for fish farming. The mean detection period after first introduction was 4 years, a duration insufficient to prevent their pan‐continental invasion. High phenotypic plasticity in fitness related traits such as growth, early maturity, fecundity, reproductive behaviour and the ability to cope with novel pathogens has predisposed P. parva to being a strong invader. The Pseudorasbora parva invasion has provided quantitative data for the development of 1) early warning systems across different spatial scales; 2) rapid eradication programmes prior to natural spread in open systems and 3) sound risk assessments with emphasis on plasticity of life history traits.