Strategies for Successful Scallops Spat Collection on Artificial Collectors in the Taranto Gulf (Mediterranean Sea)

The high variability in natural recruitment of Pectinidae is a common feature of many marine invertebrates with a pelagic larval stage, but may negatively affect aquaculture activities. Detailed information on settlement patterns and spat availability is required to reduce costs and labor. In this regard, we attempted to establish the precise immersion time and the deployment dates for spat collectors in the Taranto Gulf (Mediterranean Sea, Italy). The first experiment was carried out from June to October 2013, deploying collectors every 15 days and retrieving them after 4, 6, 8, and 10 weeks. Results from the first experiment allowed us to select 8 weeks as the best immersion time for spat collection. The second experiment was carried out from June 2013 to July 2014 when we deployed spat collectors every 15 days and recovered them after 8 weeks to detect the favorable periods to place the collectors in water to obtain the highest scallop spat harvest rate. Mimachlamys varia was the most abundant pectinid (greater than 90%), whose recruits were collected during most of the year studied, followed by Flexopecten glaber with the highest rates in July (87%) and Pecten jacobaeus, which never exceeded 17% of collected spat. M. varia had a long recruitment period (from October to early June), F. glaber showed a high number of spat during autumn months and from June to July while P. jacobaeus showed a restricted period of spawning. Our experiments provide useful insights into strategies for establishing scallop aquaculture in order to promote these mollusks as alternative candidates for aquaculture farming in the area.

Polish Regional Elite Career Paths and the Impact of a Multilevel System

This paper aims to investigate the multilevel careers of members of Polish regional executives from the first direct election to regional parliaments in 1998 until the end of 2014. Formation of self-government in regions is assumed to have started the process of formation of the multilevel system in Poland. Consequently, political career paths began to be diversified and to take place at more than one level. Among the factors with a critical impact on the specificity of Polish regional careers was the fact that regionalisation was preceded by local government reform (1990), and it was assumed that the local elite would become its natural recruitment base. On the one hand, the challenge to the development of the multilevel system has to be recognised. First, regional politics has undergone rather limited professionalisation (only positions in regional executives are full-time political jobs). Second, the legacy of communist centralisation resulted in lukewarm regional decentralisation in 1998. However, one can observe a certain increased prominence of self-government due to access to EU funds and increased financial autonomy. Positions in regional executive boards, especially as heads of regional boards [marszałkowie], have been seen as increasingly attractive career choices for professional politicians. Therefore, modification of the traditional career model is expected, e.g. some inflow of national politicians into regional boards (from positions in the legislature to executive posts).

Autotoxicity Hinders the Natural Regeneration of Cinnamomum migao H. W. Li in Southwest China

Autotoxicity is a widespread phenomenon in nature and is considered to be the main factor affecting new natural recruitment of plant populations, which was proven in many natural populations. Cinnamomum migao H. W. Li is an endemic medicinal woody plant species mainly distributed in Southwestern China and is defined as an endangered species by the Red Paper of Endangered Plants in China. The lack of seedlings is considered a key reason for population degeneration; however, no studies were conducted to explain its causes. C. migao contains substances with high allelopathic potential, such as terpenoids, phenolics, and flavonoids, and has strong allelopathic effects on other species. Therefore, we speculate that one of the reasons for C. migao seedling scarcity in the wild is that it exhibits autotoxic allelopathy. In this study, which was performed from the perspective of autotoxicity, we collected leaves, pericarp, seeds, and branches of the same population; we simulated the effects of decomposition and release of litter from these different anatomical parts of C. migao in the field; and we conducted 210-day control experiments on seedling growth, with different concentration gradients, using associated aqueous extracts. The results showed that the leaf aqueous extract (leafAE) significantly inhibited growth indicators and increased damage of the lipid structure of the cell membrane of seedlings, suggesting that autotoxicity from C. migao is a factor restraining seedling growth. The results of the analyses of soil properties showed that, compared with the other treatments, leafAE treatment inhibited soil enzyme activity and also had an impact on soil fungi. Although leafAE could promote soil fertility to some extent, it did not change the effect of autotoxic substances on seedling growth. We conclude that autotoxicity is the main obstacle inhibiting seedling growth and the factor restraining the natural regeneration of C. migao.

Evidence of Limited Recruitment of Pallid Sturgeon in the Lower Missouri River

Pallid Sturgeon Scaphirhynchus albus are endemic to the Missouri and Mississippi river basins and are rare throughout their range. The species was listed as federally endangered with little to no evidence of natural recruitment. Since population augmentation was initiated as a recovery objective in the early 1990s, thousands of hatchery-origin Pallid Sturgeon have been stocked in the lower Missouri River (Gavins Point Dam [river kilometer 1,305.1] to the confluence of the Mississippi River [river kilometer 0.0]). Efforts to discriminate natural reproduction and recruitment of wild-origin Pallid Sturgeon from hatchery-origin fish has been hampered by tag loss in hatchery-origin sturgeon, inconsistent documentation of hatchery parental crosses, and the failure to collect tissue samples for genotyping all broodstock. However, the recent reconstruction of missing parental genotypes from known hatchery-origin progeny and from cryopreserved milt made it possible to examine Pallid Sturgeon recruitment. Therefore, our objectives were to 1) determine the likelihood that unmarked Pallid Sturgeon captured from the lower Missouri River were the result of natural recruitment and 2) examine the length distribution of wild- and hatchery-origin fish to determine if a difference exists by origin and examine the life-stage distribution. Genetic analysis showed that from 2003 to 2015, 358 “presumptive wild-origin” Pallid Sturgeon were captured in the lower Missouri River and the comparison between the length distributions of wild- and hatchery-origin fish did not provide any additional clarification into potential wild-origin fish. Low recruitment may be due to a small breeding population, high mortality of early life stages, hybridization with Shovelnose Sturgeon Scaphirhynchus platorynchus, or transport of drifting free embryos or larvae into inhospitable habitats. Determining what factors are limiting recruitment is the important next step for the recovery of Pallid Sturgeon in the lower Missouri River.

Eroding productivity of walleye populations in northern Wisconsin lakes

Managing fisheries through rapid environmental change requires diverse approaches for identifying and adapting to novel ecological conditions. For the Wisconsin Ceded Territory, we calculated 473 adult walleye (Sander vitreus) production (P), biomass (B), and P/B estimates for 1990–2012. Frequency distributions for production statistics were right-skewed, indicating the fishery is generally dominated by low production populations. Mean P, B, and P/B were significantly elevated in natural recruitment (NR) lakes compared with combination (NR + stocking) and stocked-only lakes. Furthermore, combination populations had significantly higher production compared with stocked-only lakes. In NR lakes, walleye productivity changed little over time; however, the proportion of NR populations has declined over time. In combination and stocked-only populations, there were significant temporal declines in P, B, and P/B, and the proportion of these lakes has increased through time. This study reveals the crucial link between fish recruitment potential and fish production, helping to explain why the regional walleye fishery is struggling. Causes for walleye recruitment and production declines remain unclear, but long-term shifts in fish habitats are likely involved (e.g., from climate change and indirect food web effects). Decreasing walleye production is an important and emerging fishery management challenge in the region and portends a need to adapt fisheries management systems collaboratively for future sustainability.

Maternal effects better predict walleye recruitment in Escanaba Lake, Wisconsin, 1957–2015: implications for regulations

Maternal influences on age-0 walleye (Sander vitreus (Mitchill, 1818)) recruit abundance and survival from egg to fall were observed in Escanaba Lake, Wisconsin, in 1957–2015. Annual egg production best explained variation in age-0 recruitment, compared with female relative abundance, and adult abundance (sexes combined). Age-0 recruitment was not significantly correlated with any temperature metric tested or our index of yellow perch (Perca flavescens (Mitchill, 1814)) abundance. Survival of walleye from egg to fall age-0 was positively correlated with the percent contribution of large females (>55.9 cm) to annual egg production. Mean size diversity of females by length class did not influence age-0 recruit abundance or survival over time. Evidence for maternal effects via size- and age-specific influences on fecundity and age-0 walleye survival suggest that exploitation may influence natural recruitment by altering adult female size structure. Given recent declines observed in walleye natural recruitment in the upper Midwestern USA, understanding the roles of maternal drivers and exploitation on recruitment is critical for sustainable walleye management.