Marine and Coastal Fisheries最新文献

Stock assessments are particularly resource-intensive processes. Demand for assessments typically exceeds capacity, stimulating interest in reducing stock assessment frequency for suitable species. Species with slow population growth rates, low economic importance, and low recruitment variability, like coastal sharks in the USA, have been identified as appropriate candidates for long-interim assessment periods. We conducted a Stock Synthesis–based management strategy evaluation with a threshold harvest rate control rule within the southeastern USA to assess the impact of stock assessment frequency for the slow-growing Sandbar Shark Carcharhinus plumbeus. Stock assessments for the Sandbar Shark in the southeastern USA have been conducted or updated every 4–6 years since 1998. The Sandbar Shark proved to be a particularly good candidate species for reduced assessment frequency, as noted by unaffected management procedure performance across interim periods of 1, 5, and 10 years. Management objectives, including probability of stock recovery, relative biomass level, cumulative U.S. commercial catch, and probability of overfishing, were minimally adversely impacted with interim periods equal to 15 years. Based on our findings, assessment frequency for large coastal shark species could reasonably be reduced in the future to once every 10 or more years without compromising management success.

Monitoring data is important in ecological research, but differences between and within areas or species in data collection methods could introduce bias in the analyses. Standardizing data collection is particularly important when monitoring migratory species that have a distribution that crosses several national borders. The European Eel Anguilla anguilla is an extreme example of such a species since it constitutes one stock across the entire distribution area. One important variable collected for the European Eel is maturation stage. This data is needed to monitor silver eel escapement to assess population trends. To determine maturation, data on length, weight, diameter of the eyes, and pectoral fin length are used to calculate Pankhurst eye index and Durif's silver index. In this study, we investigated effects of precision and interobserver variability on data collection relevant for maturation stage determination according to Pankhurst and Durif's indices. We found that eye diameter differed in size between the left and right eyes; however, the mean difference (0.19 mm) is probably an artifact of the large sample size (n = 16,977) and can be regarded as being within the measurement precision. Meanwhile, there was no significant difference in pectoral fin length. These results suggest that either side of the eel could be used without losing precision. Visually determined maturation stage classifications differed from those calculated with Pankhurst and Durif's indices but could still provide useful information; hence, it is recommended to collect this variable. Measurements performed using computer software generated greater precision than using calipers, which increased interobserver variability. Since the difference was relatively small and since computer analysis of images may not always be an option, measuring method can be decided based on the level of precision needed in each case. These suggested implementations can reduce observation bias and streamline the data collection used for stock assessments of the European Eel.

Meteorological disturbances, such as hurricanes, can cause wide distributional changes to fish populations, but studies documenting fish movement in response to these disturbances are rare and serendipitous. We opportunistically examined how a hurricane influenced behavior of Red Snapper Lutjanus campechanus at an artificial reef complex in the western Gulf of Mexico. Red Snapper had a variety of responses, with some fish emigrating and some remaining on site during Hurricane Harvey—a category 4 storm. Hurricane-induced destruction or alteration of habitat may alter space use behavior of fish. However, caution should be used when interpreting behavior without the inclusion of array performance, which may change due to environmental conditions. Importantly, when acoustic array efficiency was not accounted for in space use analyses, mean kernel utilization distribution (m³) was marginally different among the periods before, during, and after Hurricane Harvey. However, when mean daily array efficiency was included as a covariate, space use among the three periods was not significantly different. Hurricanes can affect the movement and residency of marine species and can be an important driver in the displacement of populations and degradation of habitats, but array efficiency should be incorporated to prevent misinterpreting the behaviors of tagged fish.

Biological parameters relating to the reproductive biology of Conguito Sea Catfish Cathorops liropus were investigated in 1979–1984 and 2015–2018 from an estuarine system on the northwestern Pacific coast of Mexico. In the first period, the spawning season occurred during the dry–warm season (April–June), according with the percentage of mature females and the highest gonadosomatic index (GSI) values. Mean TL was 12.3 cm, two cohorts were found, length at maturity was 18.6 cm, and fecundity was 24.47 oocytes/organism. In the second period, the spawning season extended to the rainy–warm season (July–November), as reflected by the percentage of mature females and the GSI values. Mean TL was 11.6 cm, length at maturity decreased to 17.1 cm, and fecundity decreased to 20.67 oocytes/organism, indicating a reduction in the size-based indicators and a change in the spawning period and reproductive effort as time passed. The number of fishing skiffs increased from 1,103 in 1980 to 2,434 in 2019, representing a 220% increase, and the landings increased from 400 to 3,432 metric tons in the same period. Temporal trends in surface water temperature, salinity, and the Oceanic Niño Index did not explain the observed changes between the study periods. These results suggest that the observed changes in the reproductive potential of Conguito Sea Catfish have been at least partially due to fishing.

As climate change accelerates and fisheries management continues to evolve, California's commercial fisheries are changing. To improve the understanding of recent California fisheries dynamics, we compiled and analyzed commercial landings receipts to characterize temporal and spatial variation in landing and value of key fisheries groups within the exclusive economic zone across the state from 2005 to 2019. We found that California fisheries continue a shift first observed in the 1980s from higher-biomass, lower-value species, such as coastal pelagic species and market squid, toward lower-biomass, higher-value species, such as Dungeness crab Cancer magister and groundfish. Over the 15-year time series analyzed, total landings declined by nearly two-thirds but total value remained relatively stable, likely due to a focus on higher value species and rising prices. The northern half of the state has become much more economically valuable, accounting for over 50% of total value across the state in 2019. A case study analysis found groundfish to be the dominant fisheries in the two areas that have been identified as priorities for potential offshore wind development in central and northern California. Our results elucidate the most recent status and trends of California's commercial fisheries, over time, across space, and among different fisheries groups, providing valuable information for informing fisheries management and marine spatial planning.

Sensitivity analyses have identified uncertainty regarding sex ratios within commercial landings of Pacific Halibut Hippoglossus stenolepis as an influential source of variance within annual stock assessments for this species in U.S. and Canadian waters. Sex composition of dockside landings cannot be directly observed because all retained fish must be eviscerated at sea, and sex cannot be visually determined in the absence of the gonads. In the current study, a marking program was evaluated in which sex-specific marks were applied by fishers to their retained catch, the mark was recorded during dockside monitoring, and the accuracy of the recorded sexes was validated using genetic techniques. The chosen marks (two vertical cuts in the dorsal fin for females and a single cut in the operculum of males) were considered by fishers to be easy to apply during at-sea processing and produced sex-ratio estimates that were equivalent to genetic results for 65% of sampled landings. However, vessel- and region-specific accuracy was variable. Additional incentives to encourage vessels to participate in the program, continued outreach, or potentially a regulatory requirement to mark fish would be required to produce sufficient data to satisfy stock assessment needs, and ongoing validation would likely need to accompany such a program to ensure consistent and acceptable data quality.

The reproductive biology of the heavily exploited Pacific Spadenose Shark Scoliodon macrorhynchos was studied by examining 246 males and 197 females, including 64 gestational individuals, caught by semi-industrial fisheries using demersal trawling in the southern Taiwan Strait. Total length (L_T) at 50% maturity (L₅₀) was estimated at 464 mm L_T for males and 429 mm L_T for females. The annual reproductive cycle was determined based on the percentage of pregnant mature females and the concurrent vitellogenesis with embryonic development. Mating occurred from August to December, as evidenced by the presence of females with fresh mating injuries on their body surface and spermatozoa in the cloaca and uteri. The monthly change of embryo size indicated that parturition occurred between June and August after 5–6 months of gestation, with an L_T of 190–218 mm at birth. The litter size, which ranged from 1 to 20 pups with a mean ± SD of 9.4 ± 3.9 pups (n = 64), was positively correlated with the maternal L_T. Altogether, these findings provide valuable information that is needed for the adequate management and conservation of Pacific Spadenose Sharks in the southern Taiwan Strait and adjacent waters.

The Yangtze River Estuary (YRE) plays an important role in the conservation of fishery resources in the Yangtze River basin, and the Chinese government has established a special fishing ban management area at the YRE. To assess effects of the fishing ban, survey design and appropriate effort need to be determined and implemented. This study used long-term trawl survey data of the YRE (2004–2017) to explore the effects of survey effort (8–30 continuous survey stations selected by systematic and stratified sampling) on precision and accuracy of estimates of abundance of different fishery groups in the YRE. Estimated precision for a given number of survey stations varied by season and fishery group. Precision of systematic sampling fluctuated with the number of stations. Precision of stratified sampling with a proportional allocation scheme gradually increased with the number of survey stations. We suggest including 15–20 survey stations for all fishery groups sampled using the examined sampling methods.This study provides a research reference for selecting the survey effort (number of survey stations) for a fishery-independent survey in the YRE under the backgroud of conservation.

In 2006–2007, 110 Yellowfin Tuna Thunnus albacares were tagged with acoustic transmitters near deepwater oil platforms and one drillship in the northern Gulf of Mexico off the Mississippi River delta to determine the extent to which platforms act as fish aggregating devices (FADs). Vemco acoustic receivers were installed on six deepwater platforms to detect the presence of tagged individuals. Five of 12 Yellowfin Tuna captured in 2006 were detected in 2007, demonstrating multi-year presence in the region. Ninety Yellowfin Tuna were detected in 2007, resulting in 221 platform residencies and 32 single detections. Duration of residence at a platform was positively correlated with the platform's depth, and the number of transitions decreased with platform-to-platform distance. In total, 109 movements between platforms by 46 (51%) different individuals were detected, traveling distances of up to 98.2 km. Yellowfin Tuna displayed interactions with deepwater platforms in the northern Gulf of Mexico similar to their interactions with FADs and other studied geological features, by way of aggregating or using them as meeting points, landmarks, and stopovers within a movement corridor. The large number of oil and gas platforms located in the northern Gulf of Mexico may have a significant effect on distribution, retention, and migration of Yellowfin Tuna populations in this area of the gulf.