Recruitment of burbot (Lota lota L.) in Lake Erie: an empirical modelling approach

Stapanian MA, Witzel LD, Cook A. Recruitment of burbot (Lota lota L.) in Lake Erie: an empirical modelling approach.
Ecology of Freshwater Fish 2010: 19: 326–337. Published 2010. This article is a US Government work and is in the public domain in the USA Abstract – World‐wide, many burbot Lota lota (L.) populations have been extirpated or are otherwise in need of conservation measures. By contrast, burbot made a dramatic recovery in Lake Erie during 1993–2001 but declined during 2002–2007, due in part to a sharp decrease in recruitment. We used Akaike’s Information Criterion to evaluate 129 linear regression models that included all combinations of one to seven ecological indices as predictors of burbot recruitment. Two models were substantially supported by the data: (i) the number of days in which water temperatures were within optimal ranges for burbot spawning and development combined with biomass of yearling and older (YAO) yellow perch Perca flavescens (Mitchill); and (ii) biomass of YAO yellow perch. Warmer winter water temperatures and increases in yellow perch biomass were associated with decreases in burbot recruitment. Continued warm winter water temperatures could result in declines in burbot recruitment, particularly in the southern part of the species’ range.     

Burbot and large hydropower in North America: benefits,threats and research needs for mitigation

In North America, burbot Lota lota (L.), interactions with hydropower are common, southern burbot populations are endangered and hydropower has been implicated in the decline. Thus, the objectives of this review were to identify threats and benefits of hydropower to riverine and reservoir dwelling burbot, assess overall impacts and identify key research needs for mitigation. Review findings suggest that while winter hydropower discharge regimes threaten riverine burbot spawning, burbot often successfully exploit reservoir environments. Further, while turbine entrainment has been hypothesised as a factor in the decline of burbot populations, low adult vulnerability to passage and a high resilience to juvenile removals likely mean risk to populations is low. Identified research needs include better definitions of flow and temperature requirements for riverine burbot and a quantification of the potential for reservoirs to act as source populations for downstream impacted zones. This review highlights the Pacific watershed focus of existing work and calls for status assessments and ecological research of burbot in North American Arctic and Atlantic watersheds where large hydropower and burbot interactions are common yet rarely studied.     

Coastal river connectivity and the distribution of ascending juvenile European eel (Anguilla anguilla L.): Implications for conservation strategies regarding fish‐passage solutions

1. Many diadromous fish populations are declining and at risk of collapse. Lack of river connectivity is a major contributor to these declines, as free migration routes between marine and freshwater habitats are crucial for life‐history completion. For the conservation and ultimately recovery of such species, it is imperative that remedial measures aimed at increasing connectivity are effective.
2. This study investigated the distribution patterns of ascending juvenile European eel (Anguilla anguilla L.) in rivers in south‐western Sweden, with a focus on the effects of barriers and measures that aim to reduce the impact of barriers, i.e. fish‐passage solutions (FPSs).
3. Eel occurrence data were spatially and temporally integrated with the national databases of dams and FPSs in a Geographic Information System (GIS) environment to evaluate their effect on ascending eel distribution. The types of barriers assessed were: (i) dams with nature‐like fishways; (ii) dams with eel ramps; (iii) dams with technical fishways; and (iv) dams without FPSs.
4. Dams fitted with eel ramps or technical fishways, as well as dams without FPSs, produced a significant negative effect on the probability of eel occurrence upstream. This negative effect was not found for dams fitted with nature‐like fishways, indicating that these solutions may function better than the other FPS types in this study. The probability of eel occurrence decreased with distance from the sea and increased with area sampled, number of electrofishing runs, water temperature, and with the size of the bottom substrate.
5. We suggest that future conservation strategies for improving the natural immigration of juvenile eels should include optimizing FPS function (e.g. placement and design), the continued maintenance of FPSs, the construction of nature‐like fishways, and preferably the removal of dams, which will also benefit the downstream migration of maturing eels as well as restoring other ecosystem services.

     

Angling for endangered fish: conservation problem or conservation action?

Recreational angling has been implicated in population declines of some marine and freshwater fish, but this activity is rarely considered as a threat or even halted when endangered species are targeted. Indeed, in some cases, anglers are drawn to fish for rare or endangered species. Conservation‐oriented behaviours such as catch‐and‐release are often practiced voluntarily due to the ethics of anglers, yet even in these cases, some fishing mortality occurs. Nonetheless, there are many indirect conservation benefits associated with recreational angling. Here, we present a series of case‐studies and consider whether catch‐and‐release angling for endangered fish is a conservation problem or a conservation action. If recreational angling activities contribute to population‐level consequences that are contrary to recovery strategies, then angling for endangered species would seem to be a poor option. However, as revealed by several case‐studies, there is much evidence that anglers are vocal and effective proponents of fish and habitat conservation, and for endangered species, they are often the only voice when other stakeholders are not engaged. Anglers may contribute directly to conservation actions via user fees (e.g. licences), philanthropic donations or by volunteering in research, education and restoration activities. However, it is important to quantify post‐release mortality as well as understand the full suite of factors influencing a given population or species to know the potential risks. A risk assessment approach outlined in the paper may be used by managers to determine when the benefits of angling for endangered species outweigh the risks.     

Sampling techniques for burbot in a western non‐wadeable river

Burbot, Lota lota (L.), populations are declining throughout much of their native distribution. Although numerous aspects of burbot ecology are well understood, less is known about effective sampling techniques for burbot in lotic systems. Occupancy models were used to estimate the probability of detection () for three gears (6.4‐ and 19‐mm bar mesh hoop nets, night electric fishing), within the context of various habitat characteristics. During the summer, night electric fishing had the highest estimated detection probability for both juvenile (, 95% C.I.; 0.35, 0.26–0.46) and adult (0.30, 0.20–0.41) burbot. However, small‐mesh hoop nets (6.4‐mm bar mesh) had similar detection probabilities to night electric fishing for both juvenile (0.26, 0.17–0.36) and adult (0.27, 0.18–0.39) burbot during the summer. In autumn, a similar overlap between detection probabilities was observed for juvenile and adult burbot. Small‐mesh hoop nets had the highest estimated probability of detection for both juvenile and adult burbot (0.46, 0.33–0.59), whereas night electric fishing had a detection probability of 0.39 (0.28–0.52) for juvenile and adult burbot. By using detection probabilities to compare gears, the most effective sampling technique can be identified, leading to increased species detections and more effective management of burbot.     

Trends in Chinook salmon spawner abundance and total run size highlight linkages between life history,geography and decline

Chinook salmon (Oncorhynchus tshawytscha, Salmonidae) are foundational to social-ecological systems of the Northeast Pacific Rim and exhibit a rich diversity of life histories including in their adult migration timing, age at critical life-history transitions and marine feeding distributions. In recent decades Chinook have experienced declines across much of their native range; however, changes in productivity and abundance have rarely been evaluated in relation to life-history variation. To understand trends in Chinook salmon production, and how they are related to life history, we compiled time series data from the Fraser River to the Sacramento River on total run size (pre-fishery abundance) and escapement (post-fishery spawner abundance) and fit time series models to estimate trends across this bioregion. Our analysis revealed that most Chinook populations are declining, with negative trends in escapement (57 of 79) and total run (16 of 23) size. Trends were most acutely negative for interior spring Chinook in the Fraser, Columbia and Snake Rivers and most populations in California. Summer and fall Chinook had mixed trends, with several summer and fall upriver bright populations in the interior Columbia and Fraser exhibiting increases in abundance from the 1990s to 2019. Our research reveals widespread declines of this important species, but local complexity in trends that are mediated by population-level life history, migratory behaviours and watershed-scale restoration actions. Understanding linkages between life histories and resilience should inform rebuilding efforts for Chinook salmon and highlight the need to conserve intraspecific biodiversity.     

Shining a light on the loss of rheophilic fish habitat in lowland rivers as a forgotten consequence of barriers,and its implications for management

1. The majority of rivers around Europe have been modified in one way or another, and no longer have an original, continuous flow from source to outlet. The presence of weirs and dams has altered habitats, thus affecting the wildlife that lives within them. This is especially true for migrating rheophilic fish species, which, in addition to safe passage, depend on gradient and fast‐flowing waters for reproductive success and early development.
2. Thus far, research has focused on investigating the impacts of weirs and dams on fish passage, with less attention paid to the loss of habitat entrained by such infrastructure. The loss of rheophilic habitat is particularly important in lowland streams, where gradient is limited, and dams and weirs can be constructed with less effort.
3. Denmark is considered a typical lowland country, where the landscape around streams and rivers has been modified by agriculture and other human activities for centuries, leaving management practitioners wondering how much change is acceptable to maintain sustainable fish populations and fisheries practices.
4. With examples from Denmark, this paper attempts to conceptualize the loss in habitat as a result of barriers in lowland streams and rivers, and the repercussions that such alterations may have on rheophilic fish populations. Furthermore, the need for management to address habitat loss and its related consequences concurrently with the improvement of fish passage is emphasized.

     

The Achilles heel for spiny lobsters: the energetics of the non‐feeding post‐larval stage

Spiny lobsters are highly valuable seafood species that are captured and marketed in more than 90 countries. After more than 30 years of stable catches, spiny lobster fisheries in many parts of the world are declining due to decreased recruitment. The planktonic larvae spend up to 2 years in offshore waters, accumulating energy stores to fuel the non‐feeding post‐larva, or puerulus, to actively migrate onshore and settle. The total energy required by spiny lobster pueruli for cross‐shelf migration has not been accurately determined. Recent advances in larval culture have provided the opportunity for the first detailed examination of the swimming performance, respiratory metabolism and nitrogen excretion of spiny lobster (Sagmariasus verreauxi) throughout the puerulus stage. The routine and active metabolic rates of pueruli were lower than for most other decapod larvae, probably to provide greater energy efficiency. However, pueruli were found to have limited time, swimming ability and fuel for active cross‐shelf migration. It is estimated that S. verreauxi pueruli require at least 13.8 mg of stored lipid to provide sufficient energy (18.4% DW) to complete the puerulus stage and recruit to coastal habitats. The ability of the preceding phyllosoma larvae to accumulate these reserves, and the presence of favourable oceanographic conditions during the limited time available to the migrating puerulus, are both crucial to subsequent successful recruitment. Spiny lobster recruitment processes appear to be particularly vulnerable to changes in oceanic climate which is likely to contribute to the recent large‐scale declines in recruitment to valuable fished populations.     

Endangered farm animal breeds in German-speaking countries. II. Cattle

The development of farm animals since the beginning of domestication is described. Modern breeds have existed since the end of the 18th century. Different efficiency with regard to what were topical breeding aims as well as manipulations by the government led to a decrease in the variety of breeds. The reasons of preserving endangered breeds are both genetic and cultural. There are some examples of breeds that once had little attention payed to and which now have obtained economic importance again. In recent years several institutions in West Germany have tried by financial advancement and other measures for a variety of breeds to avoid further curtailment of them.     

Endangered domestic animal species in German speaking countries. I: General aspects

The development of farm animals since the beginning of domestication is described. Modern breeds have existed since the end of the 18th century. Different efficiency with regard to what were topical breeding aims as well as manipulations by the government led to a decrease in the variety of breeds. The reasons of preserving endangered breeds are both genetic and cultural. There are some examples of breeds that once had little attention payed to and which now have obtained economic importance again. In recent years several institutions in West Germany have tried by financial advancement and other measures for a variety of breeds to avoid further curtailment of them.