Evaluating effort regulation in mixed fisheries: a Monte Carlo approach

This paper evaluates whether effort regulation could achieve the goal of protecting low-abundance species in mixed fisheries. We construct a two-species bio-economic model and compare the stock abundance ratio in the end of the fishing season with the ratio prior to the fishing. Fishers’ profit maximization problem is governed by three key factors: (a) the overall efficiency of catching different species (catchability), (b) the price of different species, and (c) their ability to catch the favoured species separately from the less-favoured species (separability). Using a Monte Carlo sampling of feasible parameters space, we show that effort regulation has good chances (87% of the cases) of maintaining the end stock ratio near equal levels ( 1/2 < stock ratio < 2) when the initial stock ratio is equal. If the initial stock ratio is not equal, however, there is a high risk (about 50% of the cases) that effort control increases differences in the relative species abundances, rather than diminishing them. The effects depend on whether the key factors determining fishing profitability are counteracting or reinforcing each other, and their relative strength. Our results warn against placing too much faith on the ability of effort regulation to protect species at low abundances from excessive exploitation.submittedVersio

Is there a generational shift in preferences for forest carbon sequestration vs. preservation of agricultural landscapes?

Afforestation and reforestation are considered important measures for climate change mitigation. Because the land area available for tree planting may serve multiple purposes, striking the right balance between climate goals and other objectives is crucial. We conducted a survey of the Norwegian population to investigate potential land-use conflicts that may arise from executing a large-scale afforestation programme. Respondents were presented with three land-use alternatives to replace formerly grazed agricultural land. We used manipulated landscape photos to elicit their underlying value orientations. We combined multiple correspondence analysis with latent class regression models to reveal preference heterogeneity. Our models grouped respondents into three latent classes, with 24%, 24% and 52%, respectively, expressing a preference for forest carbon sequestration, recreation or agriculture as the most crucial land-use function to be retained. Birth year emerged as a strong predictor of class membership. Specifically, generations born before 1970 were more inclined to support the continuation of agricultural landscapes, while those born in 1980 and later showed a stronger inclination towards natural forest succession for carbon sequestration or recreational purposes. Quantitatively, every 10-year reduction in age increased the odds of a respondent belonging to the forestation or recreation class (relative to the agricultural class) by a factor of 2. Interestingly, even among respondents who were classified as most climate concerned, natural forests were 50% more likely to be preferred over monoculture spruce plantation as a policy option. This suggests that there may be public resistance to spruce planting for climate mitigation purposes in Norway.publishedVersio

At the Mercy of the Sea or Rational Profit-Speculators: Offshore Fishermen in Taiwan

We investigated the own- and cross-price elasticity of supply (PES) of 20 fish and shellfish species, caught in mixed fisheries off southwestern Taiwan and serving the local fresh seafood market. Because the licensed fishermen face little regulation constraining their behavior, we hypothesize that they adjust their catch profiles so as to maximize the expected value of their catch, instead of fishing indiscriminately at the mercy of the elements. However, because catches are auctioned after the landing, fishermen face uncertain price. Using daily data from 2001--2015, we found that price-taking fishermen are capable to respond to price changes of 17 of the 20 species by shifting the catch profile. The species with the highest PES are those corresponding to the highest revenues, and the fishermen are the most price elastic during the season when the catches are highest. Input substitution effect and by-catch effect offset each other, leading to weak and mostly insignificant cross-PES for most of the species. Weather conditions such as wave height, wind speed and wind direction do not appear to affect fishermen's targeting decisions for most of the 20 species, but they do affect fishermen's exit decision, i.e., going fishing or not

Gaussian mixture models reveal highly diverse targeting tactics in a coastal fishing fleet

Fishermen make repeated choices with respect to when, where, and how to catch their target species. While these targeting tactics—and the factors shaping them—are known to fishers and some experts, knowledge about them is largely informal and not well utilized for management purposes. To formalize information on targeting tactics, we propose a set of methods combining model-based classification of target species with generalized linear models. We apply these methods to Norwegian coastal fishing vessels that caught Atlantic cod (Gadus morhua) as a part of their catch portfolio in 2019. The data contains nearly 32000 fishing trips by 761 vessels. Gaussian mixture models identify eight latent targeting tactics. Cod contributes significantly to three of the tactics. The Herfindahl–Hirschman Index, a measure of vessel-level diversity of tactics, shows that one quarter of the vessels had a specialized strategy (targeting cod plus at most one additional tactic). While cod is often studied as a single-species fishery, we show that cod-catching vessels can be engaged in relatively pure fisheries during some fishing trips but switch to different, often more mixed targets during other trips. We term this as “sequential mixed fisheries”. This is both a challenge and an opportunity for the fisheries management.publishedVersio

Explaining landscape preference heterogeneity using machine learning-based survey analysis

We conducted a national survey on a high-quality internet panel to study landscape preferences in Norway, using photos as stimuli. We examined preference heterogeneity with respect to socio-demographic characteristics and latent topics brought up by the respondents, using ordinal logistic regression and structural topic modelling (STM), a machine learning-based analysis. We found that pasture landscapes are the most favoured (55%), while densely planted spruce forests are the least favoured (8%). The contrast was particularly strong between eastern and western Norway, between men and women, and between young and old. STM revealed that the choices were mainly driven by the preference for landscape openness, especially by women. Other important drivers were concerns regarding reforestation of former farmlands, aesthetic properties, forest management, biodiversity issues, and cultural values. Our results suggest that landscape policies may clash with socio-cultural preferences, and failure to account for these may undermine the success of a policy.publishedVersio

Global warming and international fishery management : does anticipation of the temperature change matter?

This paper investigates the effects of climate-induced rising of ocean temperature on the optimal fishing policies in a two players’ non-cooperative game setting. We compare reactive management, under which the manager does not believe in or know about temperature trend, with proactive management where the manager considers the future temperature change in his decisions. We assume that the fish stock is initially solely owned by country one. As temperature rises, the stock starts spilling over to the zone of the other country and eventually becomes under its sole ownership. A stochastic dynamic programming model is developed to identify Nash management strategies for the two players. The main findings are that anticipation of temperature trend induces notable strategic interactions between two players. Knowing that it is gradually loosing the stock, country one is often harvesting more aggressively, whereas the country that is increasing its ownership harvests more conservatively. Compared to reactive management, proactive management benefits both parties in terms of their cumulative pay-offs; the biological stock is also larger much of the time. In most cases, the difference between two management regimes is subtle, but when the stock is slow-growing and highly schooling, proactive management may save it from collapse

The Day-to-day Supply Responses of a Limited-entry Mixed Fishery

Under embargo until: 2021-12-4Small-scale fishers’ short-run supply decisions are understudied, often because of data limitations. We utilize a unique dataset of daily catches and prices from a mixed-species trawl fishery in Taiwan, characterized by targeting decisions made before prices are formed. To investigate the effect of expected prices on fishers’ supply decisions, we formulate a vector error correction model in a seemingly unrelated regression system of 11 fish species. We find a price-elastic short-run supply for several species: the maximum daily price elasticity of supply (PES) ranges from 0.4 to 1.1 and is statistically significant for all but one species. The long-run PES (approx. weekly) is >1 for eight species. In contrast, elasticity with respect to wave height is weak (the median short-run elasticity is −0.4). These findings are unexpected for trawl fisheries, which are believed to have low selectivity. Our results highlight the potential that auction markets have to incentivize fishing that emphasizes quality over quantity.acceptedVersio

Evaluating effort regulation in mixed fisheries: a Monte Carlo approach

This paper evaluates whether effort regulation could achieve the goal of protecting low-abundance species in mixed fisheries. We construct a two-species bio-economic model and compare the stock abundance ratio in the end of the fishing season with the ratio prior to the fishing. Fishers’ profit maximization problem is governed by three key factors: (a) the overall efficiency of catching different species (catchability), (b) the price of different species, and (c) their ability to catch the favoured species separately from the less-favoured species (separability). Using a Monte Carlo sampling of feasible parameters space, we show that effort regulation has good chances (87% of the cases) of maintaining the end stock ratio near equal levels ( 1/2 < stock ratio < 2) when the initial stock ratio is equal. If the initial stock ratio is not equal, however, there is a high risk (about 50% of the cases) that effort control increases differences in the relative species abundances, rather than diminishing them. The effects depend on whether the key factors determining fishing profitability are counteracting or reinforcing each other, and their relative strength. Our results warn against placing too much faith on the ability of effort regulation to protect species at low abundances from excessive exploitation

The Day-to-day Supply Responses of a Limited-entry Mixed Fishery

Small-scale fishers’ short-run supply decisions are understudied, often because of data limitations. We utilize a unique dataset of daily catches and prices from a mixed-species trawl fishery in Taiwan, characterized by targeting decisions made before prices are formed. To investigate the effect of expected prices on fishers’ supply decisions, we formulate a vector error correction model in a seemingly unrelated regression system of 11 fish species. We find a price-elastic short-run supply for several species: the maximum daily price elasticity of supply (PES) ranges from 0.4 to 1.1 and is statistically significant for all but one species. The long-run PES (approx. weekly) is >1 for eight species. In contrast, elasticity with respect to wave height is weak (the median short-run elasticity is −0.4). These findings are unexpected for trawl fisheries, which are believed to have low selectivity. Our results highlight the potential that auction markets have to incentivize fishing that emphasizes quality over quantity

A novel variant of SLC4A1 for hereditary spherocytosis in a Chinese family: a case report and systematic review

Abstract Background The incidence of hereditary spherocytosis (HS) is approximately 1:2000 in the western population, while it is much lower in the Chinese population. It is difficult to make a definite diagnosis due to the variable genotypic features and the lack of well-documented evidence for HS patients. Gene sequence examination is helpful for clear diagnosis. Case presentation: We presented the case of a 29-year-old male HS patient with skin yellowness, anorexia, and cholecystolithiasis as the first manifestations. Laboratory examination of the patient and his parents showed a mild reduction in hemoglobin and mean corpuscular hemoglobin concentration, increased reticulocytes, and promotion of indirect bilirubin in the patient and his father. Furthermore, small globular red blood cells with increased osmotic fragility were observed. In particular, the eosin-5’-maleimide binding test provided the strong evidence that band 3 protein was deleted in the erythrocyte membrane. Next-generation sequencing (NGS) and Sanger sequencing further demonstrated a heterozygous nonsense variant (exon16, c.G1985A: p.W662X) in SLC4A1, inherited from his father. Thus, the patient was diagnosed with HS, and then was effectively treated. After splenectomy, the anemia was relieved without any obvious unpleasant side effects. Conclusion We report an extremely rare case of HS in China that presented with hereditary hemolytic anemia with band 3 deletion resulting from a novel variant of SLC4A1, and systematically review a large number of related literatures. This study, therefore, significantly contributes to the literature on HS