Kai Lorenzen

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University of Florida | UF · School of Forest Fisheries and Geomatics Sciences

Fisheries stock assessments are essential for science-based fisheries management. Inland fisheries pose challenges, but also provide opportunities for biological assessments that differ from those encountered in large marine fisheries for which many of our assessment methods have been developed. These include the number and diversity of fisheries,...

Fisheries management is increasingly turning to participatory approaches as a way to improve stakeholder satisfaction with management institutions and policies, reduce conflicts, enhance compliance, and achieve various other benefits. However, how these efforts are perceived by participants and their impact on actual stakeholder attitudes is rarely...

Fisheries enhancements are management approaches involving the use of aquaculture and habitat technologies (in the broadest sense) to enhance or restore fisheries. The technologies most commonly used include hatchery rearing and release of aquatic animals and provision of artificial structures such as artificial reefs. Both are associated with dist...

Fisheries stock assessments increasingly account for size-dependence in natural mortality rates, usually by modeling mortality as a power function of body length. Various empirical studies have indicated a scaling of mortality with length in the range of − 0.84 to − 1.11, but substantially different scaling exponents ranging from − 0.75 to − 1.5 ha...

Natural mortality rates (M) in fish populations vary with body size and age, often by orders of magnitude over the life cycle. Traditionally, fisheries models and stock assessment methods have treated M as constant in the recruited stock, but that axiom has been challenged on empirical and theoretical grounds, and by practical assessment needs. Rev...

Freshwater fishes are among the most biodiverse vertebrate groups and among the most threatened by anthropogenic activities. Many occur in small and geographically restricted populations that are increasingly subject to catastrophic events (hurricanes, wildfires, extreme floods and droughts), but it has rarely been possible to assess the impacts of...

Understanding stakeholder diversity can help natural resource managers tailor activities to achieve greater stakeholder satisfaction. Stakeholder diversity can be described by the concept of recreational specialization. Centrality-to-lifestyle, one subdimension of specialization that measures the psychological importance of a recreational activity...

Artificial reefs have been widely deployed with the intention of increasing fish habitat, enhancing recreational fishery opportunities and providing socio-economic benefits to surrounding communities. Substantial work has been done to understand the ecology of artificial reefs but the efficacy of artificial reefs as a management tool hinges on soci...

Blue foods are highly diverse and are supported by a wide range of ecosystems, production practices, and markets. This diversity influences resiliency of aquatic food systems, their capacity to contribute to global food security, and the spread of knowledge and adoption of innovations. Here, trends in diversity and determinants of diversity in capt...

The life history schedule of short-lived species compresses the temporal window available for harvest and exacerbates harvest timing decisions. For annual species whose populations are made up of a single year class, it is challenging yet essential to limit harvest to a level that will allow sufficient spawning escapement to sustain the population....

There is interest in stock enhancement to support fisheries for California halibut Paralichthys californicus, a regionally important yet depleted species in the Southern California Bight (SCB), U.S. A quantitative model was developed to assess the cost of increasing harvestable California halibut in the SCB via releases of cultured juveniles. Reduc...

Inland fisheries in South and Southeast Asia represent important sources of food, and many are extensively stocked. Stocking often catalyses wider changes in inland fisheries is considered in this context. Stocking can be beneficial, providing additional sources of food, incentives to manage, and income-generating opportunities. However, there are...

There is growing recognition that fisheries should be managed for all three pillars of sustainability: economic, social and environmental sustainability. Limited quantitative evidence exists on factors supporting social sustainability, much less factors that contribute to multiple dimensions of sustainability. To develop a broader understanding of...

Hydropower production is one of the greatest threats to fluvial ecosystems and freshwater biodiversity. Now that we have entered the Anthropocene, there is an opportunity to reflect on what might constitute a ‘sustainable’ Anthropocene in the context of hydropower and riverine fish populations. Considering elements of existing practices that promot...

This datasheet on Population dynamics covers Identity, Description, Further Information.

Marine recreational fishing is a popular activity enjoyed by more than 9 million Americans annually and is a driver of the American ocean-or blue-economy. To ensure that fish populations are not overexploited, the NOAA Fisheries' Marine Recreational Information Program (MRIP) monitors recreational catch through a variety of in-person, telephone, ma...

A good understanding of stock recruitment is essential for accurate stock assessment and good fisheries management. But recruitment and how it is used can be difficult to understand. This publication uses a recent Florida spotted seatrout stock assessment as an example to show how the stock-recruit relationship allows managers to determine whether...

Executive summary • Florida's diverse coastal marine fisheries are enjoyed by over a million participants and generate economic impacts of around 5 Billion US $ annually. Challenges to the sustainability of these fisheries and/or their ability to provide full benefits arise from anthropogenic habitat degradation, high and increasing fishing pressur...

Hydroelectric dams often have significant impacts on freshwater fisheries. Major impacts are known to be driven by changes in river hydrology and fish ecology, but the role of governance arrangements in mitigating or exacerbating fisheries impacts from hydropower development is less understood. This study presents an analysis of stakeholder percept...

The COVID-19 global pandemic and resulting effects on the economy and society (e.g., sheltering-in-place, alterations in transportation, changes in consumer behaviour, loss of employment) have yielded some benefits and risks to biodiversity. Here, we considered the ways the COVID-19 pandemic has influenced (or may influence) freshwater fish biodive...

The potential value of protected areas for the conservation of cetaceans is widely recognized; however, few evaluation methods exist to assess their effectiveness. In this study, a modeling approach based on long-term mark-recapture/resight data was used to assess the effectiveness of a Brazilian reserve in protecting endangered Amazon River dolphi...

Concerns about forage fish taxa declines caused by fishing or environmental change and their impact on predator populations have become an important issue in fisheries management. However, it has proven difficult to identify critical forage taxa, and elusive to establish clear linkages between forage and predator dynamics. We provide a new avenue f...

Discussions about global aquaculture production and prospects for future growth largely focus on Asia, where most global production takes place. Countries in Asia accounted for about 89% of global production in 2016. Exclusive attention to Asian aquaculture, however, overlooks the fact that “the blue revolution” is occurring in most parts of the wo...

The Gulf of Mexico Red Snapper (Lutjanus campechanus) fishery is contentious. The fishery has been intensively managed over recent decades in state and federal waters using a range of management strategies (e.g., season lengths, bag limits, size/slot limits and barotrauma reduction). Declining federal fishery season lengths have resulted in frustra...

Florida researchers and fisheries management agencies have conducted years of research on stocking, a common and popular but intensive option for improving recreational fisheries, but determining how successful it has been in Florida has been challenging. This 7-page fact sheet written by Edward V. Camp, Rick Stout, Nick Trippel, Jon Fury, Stasey W...

Harvesting of pelagic fishery resources is facilitated by using fish aggregation devices (FADs). Moored FADs are manmade structures that attract pelagic fish, thereby aggregating this thinly distributed resource in a known location where it can be effectively targeted. Use of moored FADs has been actively promoted in artisanal fisheries, including...

In fisheries ecology and stock assessment, recruitment signifies the transition from early stages of the life cycle which are characterized by environmentally-driven variability and density-dependence in mortality rates, to a recruited phase when natural mortality is largely stable and density-independent. Age or size at recruitment is an important...

There is growing interest in, and need for, improving how we communicate our science with the public. Conversations about how to make our messages simple and understandable, how to harness social media and film to reach audiences (e.g., Shiffman 2018, Danylchuk 2018), and how to engage people using the power of story (e.g., Moore and Orth 2018) are...

Religion and spirituality have long played important roles in fishery systems around the world, and yet are often neglected in modern fisheries management and research. We review current literature and analyse the major small‐scale fishery on Lake Tanganyika, Africa, to highlight how religion may mediate fishing behaviours. Our study surveyed 154 f...

Restoring juvenile habitat remains a key fisheries management action, but a persistent challenge is identifying the areas likely to most efficiently improve fishery outcomes. A spatial simulation model is presented that estimates the anticipated improvement in harvest of the Eastern King Prawn fishery in New South Wales, Australia, following potent...

Stock enhancement is a practiced management strategy for sustaining and rebuilding largemouth bass fisheries in Florida and throughout their native and introduced range. However, quantitative assessment comparing efficacy of stocking to traditional management approaches are rare. We adapt an age-structured population model that explicitly represent...

Significance The United Nations proclaims that sustainable development comprises environmental, economic, and social sustainability. Fisheries contribute to livelihoods, food security, and human health worldwide; however, as the planet’s last major hunting and gathering industry, whether, and if so, how fishing can achieve all three pillars of sust...

If you catch a fish you are not going to keep, help it survive and get back to the deep! Throwing back your unwanted catch is good practice because healthy released fish can live to grow and reproduce, which benefits the fish population and the future of fisheries. But deepwater fish can have trouble getting back where they came from without a litt...

Volunteer angler data programs can help address challenges in collecting recreational fisheries data. However, recruiting and retaining participants is difficult. This study surveyed participants in the Angler Action Program to identify motivations and barriers to participation. Results showed participants were most motivated by the desire to impro...

Increasingly recreational fisheries are being managed as socioecological systems using spatially explicit and participatory place based approaches. Such approaches require considering the spatial dynamics of a resource (fish) as well as its users (anglers). While the former is comparatively well studied, very little empirical information exists reg...

The United Nations’ (UN) 2030 Agenda for Sustainable Development defines the formidable challenge of integrating historically separate economic, social, and environmental goals into a unified ‘plan of action for people, planet, and prosperity.’ We highlight the substantial contribution inland fisheries can make towards preventing increased poverty...

The dynamics underlying fisheries stock–recruitment relationships are often obscure, especially with relatively short-lived invertebrate species such as brown shrimp Farfantepenaeus aztecus. Nonetheless, disentangling these dynamics can help reveal optimal management strategies for long-term sustainability. Species like brown shrimp are often assum...

We used an integrated bio-economic model to explore the nature of tradeoffs between conservation of fisheries resources and their use for socioeconomic benefit, as realized through the stock enhancement of recreational fisheries. The model explicitly accounted for the dynamics of wild, stocked, and naturally recruited hatchery-type fish population...

Fisheries stock enhancement, the release of hatchery-reared fish into wild fish populations with the aim of improving fisheries, is a common management strategy of variable success that also involves substantial tradeoffs between fisheries management objectives. We conducted an internet-based survey to assess attitudes towards fisheries stock enhan...

Even with long-standing management and extensive science support, North American inland fish and fisheries still face many conservation and management challenges. We used a grand challenges approach to identify critical roadblocks that if removed would help solve important problems in the management and long-term conservation of North American inla...

At present, inland fisheries are not often a national or regional governance priority and as a result, inland capture fisheries are undervalued and largely overlooked. As such they are threatened in both developing and developed countries. Indeed, due to lack of reliable data, inland fisheries have never been part of any high profile global fisheri...

Reproductive strategies comprise the timing and frequency of reproductive events and the number of offspring per reproductive event, depending on factors such as climate conditions. Therefore, species that exhibit plasticity in the allocation of reproductive effort can alter their behavior in response to climate change. Studying how the reproductiv...

Recovery of the Caribbean long-spined sea urchin Diadema antillarum from the pathogen-induced mass mortality event of 1983 has been slow and variable. Multiple studies indicate that post-mortality population densities are greatest in sheltered lagoon and back reef habitats, and that recovery is limited on forereefs where pre-mortality densities wer...

Deliberate killing for use as bait in a regional catfish (Calophysus macropterus) fishery is the primary threat affecting the survival of the Amazon river dolphin, or boto (Inia geoffrensis). Establishing and improving freshwater protected areas has been suggested as a possible course of action to protect the species. However, the ecology of the bo...

Relationships between angling effort and fish abundance have critical implications for the resilience and management of recreational fisheries, but these relationships have rarely been assessed empirically. Here, angling effort was related to fish abundance in three marine recreational fisheries in Florida, USA, through a suite of regression and ti...

http://www.un.org/depts/los/global_reporting/WOA_RegProcess.htm

This chapter describes approaches to the management of habitat, people and fish stocks that make up freshwater fisheries. Habitat management is advisable whenever habitat bottlenecks limit the productivity of a fishery. Harvest regulations are a useful conservation strategy when fishing mortality is high or specific sizes of fish are to be protecte...

Fisheries enhancements are a set of management approaches involving the use of aquaculture technologies to enhance or restore fisheries in natural ecosystems. Enhancements are widely used in inland and coastal fisheries, but have received limited attention from fisheries scientists. This paper sets out 10 reasons why fisheries scientists should car...

An integrated socioecological model was developed to evaluate the potential for stock enhancement with hatchery fishes to achieve socioeconomic and conservation objectives in recreational fisheries. As a case study, this model was applied to the red drum Sciaenops ocellatus recreational fishery in the Tampa Bay estuary, Florida, U.S.A. The results...

We studied how emigration and seasonal dynamics affect apparent survival estimates in a nursery habitat, thereby altering habitat valuation. During a 3 yr study, we marked 1917 juvenile common snook Centropomus undecimalis and resighted 85.7% with a telemetry array in 4 mangrove creeks. We grouped individuals by size class, marking year, and creek,...

Negative interactions between fishers and the Amazon River dolphin (Inia geoffrensis), or boto, have increased substantially in the last few decades. Herein, we investigate these interactions with focus on assessing fisher perceptions, attitudes, and behaviors toward botos. Moreover, we evaluate the effect that the Mamiraua Sustainable Development...

This study examined the growth, activity, metabolism and post-release survival of three groups of Florida largemouth bass Micropterus floridanus: wild-caught fish, hatchery fish reared according to standard practice (hatchery standard) and hatchery fish reared under reduced and unpredictable food provisioning (hatchery manipulated). Hatchery-standa...

At the core of fisheries management lie short term trade-offs between conserving fish populations and maximizing socioeconomic benefit, but systematic assessment of such tradeoffs is not common. We evaluated how trade-offs between wild fish conservation and the generation of socioeconomic benefits in recreational fisheries might be affected by stoc...

An important goal of recreational fisheries management is to maintain and improve angler satisfaction. This task can become increasingly complicated by angler diversity in terms of social and economic characteristics, experience, expectations and motivations. A thorough understanding of angler diversity and the relationship between angler character...

Stakeholder engagement is important in natural resource management, and research has shown that involving stakeholders often leads to better management outcomes. As such, stakeholder inclusion has been central in an initiative exploring spatially-explicit management of Florida’s snook fishery. To begin, pilot information was gathered using qualitat...

Acoustic telemetry technology has been widely used to describe temporal movement patterns and spatial distributions of aquatic organisms. Long-term acoustic monitoring studies provide continuous recording of animal movement patterns generating large and complex databases that require high demands for data visualization and summaries on different ti...

To improve understanding of uni- versus multidirectional movement, seasonal dynamics, and the role of body size in tropical and sub-tropical nursery habitat, we conducted a 4 yr study on 1917 tagged juvenile common snook Centropomus undecimalis in 4 mangrove creeks. We detected 86% of individuals marked with autonomous passive integrated transponde...

Over 1.3 billion people live on tropical coasts, primarily in developing countries. Many depend on adjacent coastal seas for food, and livelihoods. We show how trends in demography and in several local and global anthropogenic stressors are progressively degrading capacity of coastal waters to sustain these people. Far more effective approaches to...

Common snook (Centropomus undecimalis) is a popular gamefish in Florida. Much effort has been made to manage and understand the life history, population dynamics, and ecology of common snook stocks in Florida. Since the mid 1950’s, the Florida Legislature and State resource agencies have designed and implemented regulations and restrictions on gear...

Acoustic telemetry studies are used to elucidate movement patterns and habitat utilization of aquatic species. A complex acoustic telemetry study was conducted to measure fine scale and long-term movements of two species frequently found together in Florida coastal rivers: Largemouth Bass (LMB, Micropterus salmoides) and Common Snook (CS, Centropom...

Aquaculture-based enhancement of marine fisheries includes sea ranching, stock enhancement, and restocking. A rapidly evolving context and maturing science base have effectively put these approaches into the fisheries management toolbox. Among the contextual factors are (1) a rapid expansion of captive breeding and domestication to new marine speci...

In this study, an integrative review of the potential for stock enhancement is conducted to support desirable management outcomes in marine recreational fisheries, focusing on the Florida, USA, red drum fishery as a case study. Here, stock enhancement is implicitly seen as a way of simultaneously achieving both ecological objectives of sustained wi...

Rigorous assessment of species and ecosystem biology underpins responsible marine stock enhancement. Estimation of limits to stocking density, based on ecosystem productivity and energetic requirements of stocked species, can be used to gauge the appropriate magnitude of release densities, minimizing waste of resources, and the possibility for adve...

The relationship between fishing, livelihood diversification and poverty was investigated in the lower Mekong basin, in Laos, where fishing forms an important, but usually secondary part of rural livelihoods. Results from a household survey show that participation in fishing is common and positively associated with higher occupational diversity and...

Stock enhancement is increasingly considered as a management strategy to improve outcomes of commercial and recreational fisheries. Assessing enhancement outcomes requires evaluating the entire system, including socioeconomic attributes (e.g., governance, economic dynamics, and stakeholder opinions and values). We synthesized information from studi...

The state of Florida is seeking to expand its marine hatchery program for fisheries enhancement and conservation purposes. As part of this effort, a systematic process is being designed and implemented to prioritize candidate stocks for hatchery production and fisheries enhancement. The aim of this process is to identify stocks in which release of...

Hatchery rearing results in domesticated phenotypes that can affect the organism’s physiology and behavior in ways that are detrimental to fitness in the wild. Understanding how domestication effects arise and how these phenotypic changes influence survival after release are of great importance to enhancement programs. We tested whether the provisi...

Quantitative assessment of the contribution a hatchery program can make to fisheries management goals, including synergies and tradeoffs with fishing regulations and habitat management, is a key requirement if enhancements are to be effective and sustainable. Over the past decade, population dynamics models commonly used in fisheries assessments ha...

Hatchery-based enhancement and restoration programs may be developed in a variety of fisheries situations and with a view to achieving different goals. Different situations and goals may call for very different combinations of hatchery practices, release and fishing regimes. For example, ranching systems operate for species that do not recruit natu...