As the number of fish reproduction studies has proliferated, so has the number of gonadal classification schemes and terms. This has made it difficult for both scientists and resource managers to communicate and for comparisons to be made among studies. We propose the adoption of a simple, universal terminology for the phases in the reproductive cycle, which can be applied to all male and female elasmobranch and teleost fishes. These phases were chosen because they define key milestones in the reproductive cycle; the phases include immature, developing, spawning capable, regressing, and regenerating. Although the temporal sequence of events during gamete development in each phase may vary among species, each phase has specific histological and physiological markers and is conceptually universal. The immature phase can occur only once. The developing phase signals entry into the gonadotropin‐dependent stage of oogenesis and spermatogenesis and ultimately results in gonadal growth. The spawning capable phase includes (1) those fish with gamete development that is sufficiently advanced to allow for spawning within the current reproductive cycle and (2) batch‐spawning females that show signs of previous spawns (i.e., postovulatory follicle complex) and that are also capable of additional spawns during the current cycle. Within the spawning capable phase, an actively spawning subphase is defined that corresponds to hydration and ovulation in females and spermiation in males. The regressing phase indicates completion of the reproductive cycle and, for many fish, completion of the spawning season. Fish in the regenerating phase are sexually mature but reproductively inactive. Species‐specific histological criteria or classes can be incorporated within each of the universal phases, allowing for more specific divisions (subphases) while preserving the overall reproductive terminology for comparative purposes. This terminology can easily be modified for fishes with alternate reproductive strategies, such as hermaphrodites (addition of a transition phase) and livebearers (addition of a gestation phase).
Reproductive timing can be defined as the temporal pattern of reproduction over a lifetime. Although reproductive timing is highly variable in marine fishes, certain traits are universal, including sexual maturity, undergoing one or more reproductive cycles, participating in one or more spawning events within a reproductive cycle, release of eggs or offspring, aging, and death. These traits commonly occur at four temporal scales: lifetime, annual, intraseasonal, and diel. It has long been known that reproductive timing affects reproductive success, especially in terms of the onset of sexual maturity and the match or mismatch between seasonal spawning and offspring survival. However, a comprehensive understanding of variability in reproductive timing over species, populations, and temporal scales is lacking. In addition, there is a need to assess how variability in reproductive timing affects a population's resilience. Because natural selection occurs at the individual level, this necessitates an understanding of within-population (i.e., individual) variability in reproductive timing and how fishing may impact it through age truncation and size-specific selectivity or fisheries-induced evolution. In this paper, we review the temporal aspects of reproductive strategies and the four most-studied reproductive timing characteristics in fishes: sexual maturity, spawning seasonality, spawning frequency, and diel periodicity. For each characteristic, we synthesize how it has traditionally been measured, advances in understanding the underlying physiology, its role in equilibriumbased fish population dynamics, and its importance to reproductive success. We then provide a review of emerging methodology-with an emphasis on ovarian histology-to improve our ability to assess variability in reproductive timing both among populations and within populations.
This paper reviews the use of acoustic telemetry as a tool for addressing issues in fisheries management, and serves as the lead to the special Feature Issue of Ecological Applications titled Acoustic Telemetry and Fisheries Management. Specifically, we provide an overview of the ways in which acoustic telemetry can be used to inform issues central to the ecology, conservation, and management of exploited and/or imperiled fish species. Despite great strides in this area in recent years, there are comparatively few examples where data have been applied directly to influence fisheries management and policy. We review the literature on this issue, identify the strengths and weaknesses of work done to date, and highlight knowledge gaps and difficulties in applying empirical fish telemetry studies to fisheries policy and practice. We then highlight the key areas of management and policy addressed, as well as the challenges that needed to be overcome to do this. We conclude with a set of recommendations about how researchers can, in consultation with stock assessment scientists and managers, formulate testable scientific questions to address and design future studies to generate data that can be used in a meaningful way by fisheries management and conservation practitioners. We also urge the involvement of relevant stakeholders (managers, fishers, conservation societies, etc.) early on in the process (i.e., in the co-creation of research projects), so that all priority questions and issues can be addressed effectively.
Although incorporating detailed reproductive data into all stock assessments is not a practical goal, the need to understand how reproductive biology affects population productivity is being increasingly recognized. More research focused on reproductive biology—coupled with a shift towards a resilience perspective in fisheries science—is resulting in challenges to many long‐held assumptions; the emergence of important new issues; and identification of the need to improve data and methods used in reproductive studies. Typically, data for reproductive studies are based on an assessment of gonadal development, which is most accurately evaluated with histology. This special section of Marine and Coastal Fisheries contains contributions from a workshop on the gonadal histology of fishes that was held in Cadiz, Spain, during June 2009. These papers cover a wide range of species and reproductive topics while introducing improved and new histological techniques. In this introduction, we address the following needs: (1) to employ standardization, thereby improving our ability to conduct comparative studies; (2) to better understand patterns of gonadal development and spawning events over time; and (3) to move beyond the spawning stock biomass paradigm. We identify the contributions of special section papers to these topics and conclude by suggesting needs for future research and integration of reproductive data into both conceptual and quantitative models to better understand how reproductive performance affects population dynamics.
A close relationship between adult abundance and stock productivity may not exist for many marine fish stocks, resulting in concern that the management goal of maximum sustainable yield is either inefficient or risky. Although reproductive success is tightly coupled with adult abundance and fecundity in many terrestrial animals, in exploited marine fish where and when fish spawn and consequent dispersal dynamics may have a greater impact. Here, we propose an eco‐evolutionary perspective, reproductive resilience, to understand connectivity and productivity in marine fish. Reproductive resilience is the capacity of a population to maintain the reproductive success needed to result in long‐term population stability despite disturbances. A stock's reproductive resilience is driven by the underlying traits in its spawner‐recruit system, selected for over evolutionary timescales, and the ecological context within which it is operating. Spawner‐recruit systems are species specific, have both density‐dependent and fitness feedback loops and are made up of fixed, behavioural and ecologically variable traits. They operate over multiple temporal, spatial and biological scales, with trait diversity affecting reproductive resilience at both the population and individual (i.e. portfolio) scales. Models of spawner‐recruit systems fall within three categories: (i) two‐dimensional models (i.e. spawner and recruit); (ii) process‐based biophysical dispersal models which integrate physical and environmental processes into understanding recruitment; and (iii) complex spatially explicit integrated life cycle models. We review these models and their underlying assumptions about reproductive success vs. our emerging mechanistic understanding. We conclude with practical guidelines for integrating reproductive resilience into assessments of population connectivity and stock productivity.
Migration is a widespread but highly diverse component of many animal life histories. Fish migrate throughout the world's oceans, within lakes and rivers, and between the two realms, transporting matter, energy, and other species (e.g., microbes) across boundaries. Migration is therefore a process responsible for myriad ecosystem services. Many human populations depend on the presence of predictable migrations of fish for their subsistence and livelihoods. Although much research has focused on fish migration, many questions remain in our rapidly changing world. We assembled a Lennox et al. Fish Migration Questions diverse team of fundamental and applied scientists who study fish migrations in marine and freshwater environments to identify pressing unanswered questions. Our exercise revealed questions within themes related to understanding the migrating individual's internal state, navigational mechanisms, locomotor capabilities, external drivers of migration, the threats confronting migratory fish including climate change, and the role of migration. In addition, we identified key requirements for aquatic animal management, restoration, policy, and governance. Lessons revealed included the difficulties in generalizing among species and populations, and in understanding the levels of connectivity facilitated by migrating fishes. We conclude by identifying priority research needed for assuring a sustainable future for migratory fishes.
The spatial distribution of spawning activity can affect the reproductive success of certain fishes, and locating the key areas is critical to accurately assessing and managing their populations. We determined estuarine spawning locations for spotted seatrout Cynoscion nebulosus during the 2004 summer spawning season in Tampa Bay, Florida, using a passive acoustic survey. Sound production was evaluated at each of 754 randomly selected stations for the number of individuals calling and ranged from 1‐2 individuals to large aggregations. Spawning was identified by large aggregation sounds and was detected at 8% of the selected stations. There was seasonal variability in spawning, as spawning areas were inconsistently used throughout the season. Spatially, spawning occurred in all regions of the bay except for the Hillsborough Bay region. Most spawning took place in lower Tampa Bay and the eastern portion of the middle bay. Spawning occurred most frequently near the shoreline in areas of relatively high dissolved oxygen and in association with submerged aquatic vegetation. The variability in spawning habitat, as exhibited by both the disproportionate distribution of spawning sites across Tampa Bay and the inconsistent use of spawning sites, may serve to increase the resilience of the stock. As management directives evolve to encompass habitat‐focused strategies, surveys such as this one can supply data necessary for the creation of meaningful ecosystem‐based management plans.
Despite its small size, the pearly razorfish Xyrichtys novacula (Linnaeus, 1758) supports important targeted recreational and commercial fisheries. Here, we present the first data on the movements of this species obtained using acoustic telemetry in a temperate marine protected area (MPA). The results demonstrate that acoustic telemetry is well suited for behavioural studies, even in species of small size. The results confirmed previous speculations regarding the behaviour of this species, demonstrating a clear diel pattern with maximum rates of activity during the day and fewer detections at night, when the fish bury themselves in the soft bottom. X. novacula exhibited a sedentary lifestyle with limited movement. The fish occurred in an accumulated averaged area of 0.32 ± 0.13 km 2 95% of the time (95% kernel utilisation distribution [KUD]) and in a core area (50% KUD) of 0.07 ± 0.02 km 2 . These small areas of habitat utilisation existed independent of sex and diel behaviour. No daily migration pattern or specific resting locations were detected. The linearity index (as a proxy of site fidelity) demonstrated that the movement of X. novacula was random within a specific home range area (sedentary behaviour) rather than directional (nomadic behaviour). The observed diel pattern of behaviour confirms that this species is not vulnerable to nighttime fishing, and the small spatial scale of habitat utilisation suggests that small MPAs can be an effective management tool. 460: 207-220, 2012 prey (Cardinale et al. 1997, Castriota et al. 2005a, occupying a mid-trophic level within the food web (Blanco et al. 2009, Box et al. 2010. KEY WORDS: Acoustic telemetry · Continuous wavelet transform · Control tag · Home range · MPA · Protogynous hermaphrodite · Xyrichtys novacula Resale or republication not permitted without written consent of the publisherMar Ecol Prog SerSome populations of this species have been subjected to overfishing, exhibiting clear decreases in abundance and their age and size distributions as well as the size at maturation, thereby decreasing the size at sex change and affecting reproductive output (Linde & Palmer 2008). In an effort to effectively manage this species, a number of management measures have been adopted, including seasonal closures, daily bag limits and minimum sizes of hooks (e.g. Morales-Nin et al. 2010).However, the usefulness of MPAs depends on the scale of fish movement in relation to the size of the MPA (Kramer & Chapman 1999). Thus, effective MPAs must include appropriate habitats and be sufficiently large to encompass the regular movements of adult fish (i.e. their home ranges). Then, the spillover of early life stages (eggs and larvae) and the movement of adults into areas outside the MPA can only be successful (in terms of sustainability) if a stable adult population is able to persist within the protected area (Kaplan et al. 2006).Unfortunately, most management measures continue to be based on the assumption that fish populations are spatially homogeneous (Botsfo...
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