Fisheries provide countless benefits to human populations but face many threats ranging from climate change to overfishing. Despite these threats and an increase in fishing pressure globally, most stocks remain unassessed and data limited. An abundance of data-limited assessment methods exists, but each has different data requirements, caveats, and limitations. Furthermore, developing informative model priors can be difficult when little is known about the stock, and uncertain model parameters could create misleading results about stock status. Our research illustrates an approach for rapidly creating robust initial assessments of unregulated and data-limited fisheries without the need for additional data collection.
Our method uses stakeholder knowledge combined with a series of data-limited tools to identify an appropriate stock assessment method, conduct an assessment, and examine how model uncertainty influences the results. Our approach was applied to the unregulated and data-limited fishery for Crevalle Jack Caranx hippos in Florida.
Results suggested a steady increase in exploitation and a decline in stock biomass over time, with the stock currently overfished and undergoing overfishing. These findings highlight a need for management action to prevent continued stock depletion.
Our approach can help to streamline the initial assessment and management process for unregulated and data-limited stocks and serves as an additional tool for combating the many threats facing global fisheries.
Offshore wind development is expected to expand rapidly along the East Coast of the United States within the next 10 years and will impact the biology and ecology of the flora and fauna as well as human activities, such as commercial and recreational fishing. The Block Island Wind Farm is a five-turbine, 30-MW wind array located about 6 km off the coast of Rhode Island and has been in operation since 2016.
We conducted a 4-day acoustical and biological survey of the area during daylight hours to gain insight on the spatial distribution of fish species in and around the turbines. We utilized a hull-mounted, downward-looking Simrad 38-/200-kHz ES70 and a pole-mounted iXblue SeapiX steerable Mills Cross, 150-kHz, 1.6° resolution multibeam echosounder oriented downward to map the two- and three-dimensional distributions using spiral and straight-line transect patterns. We collected fish by using hook and line to verify the sources of acoustic backscatter and to measure length, sex, and diet.
Black Sea Bass Centropristis striata were the most commonly caught species and appeared to be the primary constituents of the fish aggregations that were mapped by the acoustic systems. We found increased levels of acoustic backscatter within 200 m of the turbine structures, suggesting that they were attractive structures.
These levels were not greater than backscatter levels in the surrounding area, suggesting that the proximate effect of the wind array was spatially limited.
Atlantic Menhaden Brevoortia tyrannus support fisheries that yield the largest landings by volume on the U.S. East Coast and fulfill a critical ecological role as a forage species. The spawning reference point of the stock assessment model that is routinely applied to this species requires information on total annual fecundity. The goal of this study was to generate a contemporary, histology-based evaluation of the reproductive biology and fecundity of female Atlantic Menhaden.
Female Atlantic Menhaden (n = 559) were collected between Cape Cod, Massachusetts, and Cape Hatteras, North Carolina, from 2013 to 2019. Ovarian tissues were prepared using standard histological techniques which, when coupled with oocyte size-frequency and count data, were used to classify reproductive mode and estimate batch fecundity, spawning frequency, and maturity. Monthly gonosomatic indices were combined with published female reproductive information and spatiotemporal patterns in larval and juvenile abundance to designate spawning seasonality.
Histological preparations and oocyte size-frequency patterns of female Atlantic Menhaden ovaries were consistent with indeterminate batch spawning. Batch fecundity increased with fork length, while spawning seasonality extended from September 15 to April 15 with a spawn every 7.5 ± 2.3 days. Female maturity probabilities transitioned from 0.2 to 0.8 over fork lengths of 214.8–226.5 mm (approximately ages 2.0–2.3 years). Estimated mean per capita female annual fecundity varied from 465,757 to 3,250,135 oocytes for fish ranging from 215.8 to 284.8 mm fork length (ages 2–6 years), which represented a 614–2267% (mean = 1656%) increase in annual female reproductive output relative to previous estimates.
Female Atlantic Menhaden exhibit indeterminant batch spawning while spawning seasonality and mean per capita female annual fecundity were appreciably greater than previously reported. This new reproductive information illuminates the robust reproductive productivity of this species and will aid routinely conducted stock assessments.
Along the Aleutian Islands, Light Dusky Rockfish Sebastes variabilis and Harlequin Rockfish S. variegatus are two of the more abundant species within the “Other Rockfish” management complex of this region. Many Sebastes spp. are assessed in multispecies complexes due to a lack of basic biological information to inform management. In an effort to address data gaps, we investigated age, growth, and natural mortality for both species. The larger abundance of Light Dusky Rockfish allowed for an examination of distribution across different areas of the Aleutian Islands.
Otoliths from Light Dusky Rockfish and Harlequin Rockfish were used for age determination to describe growth parameters and subsequent maximum ages used for calculating rates of natural mortality from a mean of updated age-based estimators. Generalized linear models were developed to describe the depth distribution of Light Dusky Rockfish.
Ages ranged from 3 to 79 years for Harlequin Rockfish and 3 to 70 years for Light Dusky Rockfish. Maximum ages were corroborated by multiple analyses providing estimates for natural mortality (Light Dusky Rockfish = 0.084; Harlequin Rockfish = 0.075). The von Bertalanffy growth model for Harlequin Rockfish indicated sex-specific differences, with females attaining larger maximum sizes and a lower growth coefficient. Light Dusky Rockfish showed no differences in growth by area or sex. Length distributions among areas for each species were different. Light Dusky Rockfish tended to occur in deeper water in the central and western areas of the Aleutian Islands. The presence of Light Dusky Rockfish in deeper water is influenced, through the effect in terms of odd ratios, by maturity status and area and is variable by year.
These results contribute to our understanding of the management and biology of Sebastes spp. within their complex, but additional investigations are needed, especially with how traits may differ within and between regions.
Large-scale offshore windfarms are proposed along the U.S. Northeast coast; the first is the Vineyard Wind lease area, which is planned for construction in 2023. During the fall of 2018, an experimental bottom trawl survey in the Vineyard Wind lease area and adjacent control area was conducted to collect preliminary estimates of fish assemblage composition, density, and size distribution.
Initially, a new open cod end design was tested, but poor visibility due to fine substrate rendered the gear inefficient. The survey was completed using the traditional closed-tow method.
The estimates of density and variance enabled a power analysis, which recommended a minimum of 20 tows in the development area and 20 tows in the control area to achieve a 25% chance of detecting a shift in the density of the four most abundant species.
These results led to the development of a seasonal bottom trawl survey beginning in 2019 using protocols that align with other shelfwide bottom trawl surveys.
To determine the spawning seasonality of two highly targeted jacks (Carangidae; Giant Trevally [known in Hawai’i as ulua aukea] Caranx ignobilis and Bluefin Trevally [known in Hawai’i as ‘ōmilu] Caranx melampygus) within Hawai’i through a collaborative effort with local fishers.
By working with volunteer fishers, we collected gonad samples for Giant and Bluefin trevally throughout a 15-month period on four of the main Hawaiian Islands. Spawning seasonality was assessed using histological gonad samples as well as mean monthly gonadosomatic index (GSI).
Fishery involvement proved successful in collecting biological samples needed to understand the spawning seasonality of these species. Participants were able to macroscopically identify when females were spawning versus undeveloped following initial instruction from the researchers. Mature female GSI resulted in similar conclusions as histological analyses. Both species had a spawning season between February and September, with peak spawning occurring from May to July. During the spawning months, a semilunar spawning pattern was observed for Giant Trevally with peak GSI occurring shortly before the full moon. Bluefin Trevally had higher variability, with no distinct lunar periodicity.
Training fishers to be a part of the scientific process and collect gonad samples created trust in science and interest in learning more about the biology of their catch. By consistently sharing our progress and results through social media we were able to engage and build trust with the greater fishing community.
The diamondback terrapin Malaclemys terrapin is frequently caught as bycatch in both commercial and recreational blue crab Callinectes sapidus fisheries throughout its range along the Atlantic and Gulf coasts of North America. Bycatch reduction devices (BRDs) are plastic or wire rectangles mounted in the entrance funnels of crab traps, designed to exclude terrapins while still allowing crabs to enter. In this study conducted in two tidal creeks in Virginia, USA, we assessed the effectiveness of four BRD designs, including two novel oval designs, against control traps with no BRDs.
We tested four replicates of each of the five trap treatments (1.75-inch oval BRD, 2-inch oval BRD, 1.75-inch rectangular BRD, 2-inch rectangular BRD, and a control trap without a BRD) in each tidal creek, for a total of 20 traps per creek and 40 traps total. We fitted traps with wire chimneys that extended above the high tide water line to allow trapped terrapins to surface for air. For eight weeks during summer 2021, we baited traps with Atlantic Menhaden Brevoortia tyrannus each day, beginning on Monday. Tuesday–Friday, we emptied traps of any animals inside, and recorded terrapin sex, terrapin carapace length, terrapin carapace width, and terrapin shell height, as well as blue crab carapace length.
We found that all four BRD designs were highly effective at excluding terrapins and maintaining crab catch when compared to control traps. We found a significant difference (p = 0.003) in catch per unit effort (CPUE) of diamondback terrapins among treatments, with the control group (those without BRDs) having the highest CPUE (0.97 ± 0.18). All traps fitted with BRDs decreased terrapin capture significantly compared to the control group. Oval BRDs excluded more terrapins than their rectangular counterparts with the same height dimension, although these differences were not significant. We found no significant difference in CPUE of blue crabs among treatments (p = 0.392), or in the size of legal crabs caught in each treatment (p = 0.216).
This study provides evidence of the effectiveness of both rectangular and oval-shaped BRDs to exclude terrapins and maintain crab catch in Virginia waters, where BRDs are not currently required.
Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis, collectively referred to as river herring, are anadromous clupeids inhabiting the North American Atlantic coast. Although the seasonal patterns of their spawning migration are well studied and predictable, the fine-scale movements are still poorly resolved.
This study used high-resolution acoustic imaging to study the fine-scale behavior of river herring during their spring spawning migration in two coastal rivers in Massachusetts, United States.
Observations suggest that seasonal patterns of migration appear to be influenced by temperature, while fine-scale patterns in migration were associated with the time of day, tidal state, and their interaction. River herring were consistently observed during both day and night, with elevated peaks of activity in the early morning and late afternoon. Daytime movement consisted of the intermittent passage of large, dense schools, while nighttime movement consisted of the frequent passage of individuals or small groups. The highest numbers of herring observations were associated with flood and high tides. Additionally, the interactions between time of day and tidal state resulted in synergistic positive effects during crepuscular incoming tides, which were favorable to movement, and synergistic negative effects during midday low tides, which inhibited fish movement.
The changing relationship between the time of day and tidal state within the season manifested in changing periodicity in fish movement to correlate with favorable movement conditions. Since movements may be related to both time of day and tide, previous run size estimates from visual counts made only during the day may be too low. Sampling methodologies that collect information during all 24 h would likely produce the most accurate run size estimates. This study highlights the need to view river herring migration in a holistic context predicated by multiple environmental and biological factors that vary at several temporal scales (i.e., seasonally, daily, and hourly).
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：