Spermatophore dimorphism in the chokka squid <i>Loligo reynaudii</i> associated with alternative mating tactics

Chokka squid (Loligo reynaudii) have characteristic alternative mating tactics: ‘consort’ males temporarily pair with and guard a female and transfer spermatophores onto her oviduct opening inside the mantle cavity, whereas ‘sneaker’ males rush towards a mating pair and transfer spermatophores onto the female’s buccal membrane near her sperm storage organ. Differences in mating behaviours and their related sperm-storage sites clearly constrain the fertilization process and can drive dimorphism between consort and sneaker males. The presence and character of male dimorphism has not yet been fully examined in this species, but consort males are commonly much larger than sneaker males. We observed clear dimorphism in spermatangia (the sperm mass ejaculated from the spermatophore), consistently associated with the two alternative sperm storage sites on the female’s body. Observations of spermatophores stored in the Needham’s sac of mature males confirmed that small males produce ‘sneaker-type’ spermatangia whereas larger males produce ‘consort-type’ spermatangia, and no individuals possessed both types. Therefore, by association, the mating tactic adopted (including the sperm deposition site used) by individual males can be determined from observation of their spermatangial type, without requiring direct behavioural observation of mating. This ability to infer information about mating tactic will improve our understanding of the reproductive system and mating dynamics in this species

A change of the seaward boundary of Goukamma Marine Protected Area could increase conservation and fishery benefits

Goukamma Marine Protected Area (MPA) on the South African temperate South Coast has been shown to be effective in maintaining a spawning stock of roman, Chrysoblephus laticeps (Sparidae). The larval ecology and the oceanographic conditions in the area suggest a good potential for the enhancement of roman stocks outside the reserve through larval dispersal. A high rate of illegal fishing just inside the seaward boundary of the MPA could severely compromise its function.We suggest that a change of the seaward boundary of the reserve to coincide with a latitudinal line could increase its function as a harvest refuge for resident reef fishes such as roman, facilitate voluntary compliance and monitoring and prosecution of illegal fishing without a significant negative impact on the commercial linefishing fleet in the area. Simple adjustments such as the one proposed here could be attempted at a number of South African MPAs as they would be beneficial to achieve fishery and conservation goals alike

Socio-Economic and Environmental Challenges of Small-Scale Fisheries: Prognosis for Sustainable Fisheries Management in Lake Kariba, Zambia

The Lake Kariba fishery is of regional importance; it accounts for 35% of the total Zambian fish production. However, emerging evidence in the recent decades suggests that the fishery is facing socio-economic and environmental challenges. Using Ostrom’s framework for analysing socio-ecological systems, we examined the social, economic, and environmental problems faced by the fishing communities in Lake Kariba. The framework links various social, economic, and ecological factors to devise a sustainable fisheries management plan. A combination of survey questionnaires, focus group discussions, observations, and key informant interviews were used to assess this sustainability challenge. The data collected were subjected to bivariate and descriptive analysis. The results obtained did not show a significant decline in fish production over the past 13 years (R2 Linear = 0.119, p = 0.248). However, the experts and the fishers have reported declining trends in valuable fish species such as Oreochromis mortimeri, compounded by the increased fishing efforts (X2 = 180.14, p value = ˂ 0.00001). The key threats identified include: overfishing, weak institutions, and the introduction of invasive fish species such as Oreochromis niloticus. This situation has raised fears of fish depletion among the stakeholders. Based on these results, we recommend stronger institutional collaboration among the stakeholders in the riparian states and education that illustrates the global value of fisheries for food security and biodiversity conservation in pursuing the United Nations Sustainable Development Goals

A change of the seaward boundary of Goukamma Marine Protected Area could increase conservation and fishery benefits

Goukamma Marine Protected Area (MPA) on the South African temperate South Coast has been shown to be effective in maintaining a spawning stock of roman, Chrysoblephus laticeps (Sparidae). The larval ecology and the oceanographic conditions in the area suggest a good potential for the enhancement of roman stocks outside the reserve through larval dispersal. A high rate of illegal fishing just inside the seaward boundary of the MPA could severely compromise its function. We suggest that a change of the seaward boundary of the reserve to coincide with a latitudinal line could increase its function as a harvest refuge for resident reef fishes such as roman, facilitate voluntary compliance and monitoring and prosecution of illegal fishing without a significant negative impact on the commercial linefishing fleet in the area. Simple adjustments such as the one proposed here could be attempted at a number of South African MPAs as they would be beneficial to achieve fishery and conservation goals alike

Ocean warming, a rapid distributional shift, and the hybridization of a coastal fish species

Despite increasing awareness of large-scale climate-driven distribution shifts in the marine environment, no study has linked rapid ocean warming to a shift in distribution and consequent hybridization of a marine fish species. This study describes rapid warming (0.8 °C per decade) in the coastal waters of the Angola-Benguela Frontal Zone over the last three decades and a concomitant shift by a temperature sensitive coastal fish species (Argyrosomus coronus) southward from Angola into Namibia. In this context, rapid shifts in distribution across Economic Exclusive Zones will complicate the management of fishes, particularly when there is a lack of congruence in the fisheries policy between nations. Evidence for recent hybridization between A. coronus and a congener, A. inodorus, indicate that the rapid shift in distribution of A. coronus has placed adults of the two species in contact during their spawning events. Ocean warming may therefore revert established species isolation mechanisms and alter the evolutionary history of fishes. While the consequences of the hybridization on the production of the resource remain unclear, this will most likely introduce additional layers of complexity to their management

Multiple Mating, Paternity and Complex Fertilisation Patterns in the Chokka Squid Loligo reynaudii

Polyandry is widespread and influences patterns of sexual selection, with implications for sexual conflict over mating. Assessing sperm precedence patterns is a first step towards understanding sperm competition within a female and elucidating the roles of male- and female-controlled factors. In this study behavioural field data and genetic data were combined to investigate polyandry in the chokka squid Loligo reynaudii. Microsatellite DNA-based paternity analysis revealed multiple paternity to be the norm, with 79% of broods sired by at least two males. Genetic data also determined that the male who was guarding the female at the moment of sampling was a sire in 81% of the families tested, highlighting mate guarding as a successful male tactic with postcopulatory benefits linked to sperm deposition site giving privileged access to extruded egg strings. As females lay multiple eggs in capsules (egg strings) wherein their position is not altered during maturation it is possible to describe the spatial / temporal sequence of fertilisation / sperm precedence There were four different patterns of fertilisation found among the tested egg strings: 1) unique sire; 2) dominant sire, with one or more rare sires; 3) randomly mixed paternity (two or more sires); and 4) a distinct switch in paternity occurring along the egg string. The latter pattern cannot be explained by a random use of stored sperm, and suggests postcopulatory female sperm choice. Collectively the data indicate multiple levels of male- and female-controlled influences on sperm precedence, and highlights squid as interesting models to study the interplay between sexual and natural selection

Redistribution and Transformation in the South African Fishing Industry: The Case of the Squid Fishery

This is a summary paper on the redistribution and restructuring of the South African squid industry. Political normalisation in South Africa during 1994, and the drafting of the new Marine Living Resources Act 1998, led to the imperative to transform the fishing sector to more equitably reflect the racial demographics of the country. The current approach to redistribution in the squid industry is a command and control instrument. It takes access rights, in the form of fisher permits, away from existing boat owners and redistributes them to new entrants from historically disadvantaged communities. The lack of human skills and capital - which is a persistent legacy of apartheid - of the new entrants, coupled with one year tenure of permits, has resulted in a market for paper permits. This system also results in income, rather than wealth, redistribution. An incentive market based process of transformation is proposed. It is argued that long term access rights on vessels can be used as a behavioral incentive for boat owners to internally transform their own ownership structures to reflect the demographic distribution of the country

An appraisal of fisheries science and management after 14 years of democracy in South Africa

The Constitutional imperative in South Africa after 1994 was to build a just and equitable order that would benefit its entire people's after centuries of social and legal privilege benefited ruling minorities. In 1998 new era fisheries legislation aimed to redistribute fishing access rights and reform the sector. The challenge was to take away from some and to give to others, such that fish stocks should not be compromised, social equity would be better served and yet to achieve this via democratic principles and upholding of the rule of law. Legal and social conflict was an inevitable consequence. False starts, administrative incapacity and new inequalities were given rise to. Inadequate political support, court challenges, including to the highest Constitutional court, followed from those who felt too little had been allocated their way and from those who felt too much had been taken from them. By 2008 the conflict was still not settled. How can monopolistic features of a modern, high investment industry, able to maximize the value of its product be maintained in part but at the same time meet fishing community expectations and return historic rights in a new dispensation, but one that enshrines capitalist principles. We examine the effect of the allocation of long term rights in South Africa and the state of marine science and marine resources fourteen years into the new dispensation. The paper is a first attempt to draw a dispassionate environmental balance sheet in this complex set of competing factors. Are marine resources the inevitable loser in battlefield field of human accommodations

Sustainable seafood using octopus as a model

The global catch of octopus and squid shows annual variability and demand is likely to increase for both locally-supplied and imported products. However, the vulnerability of seafood resources is now well known, the reliability of fisheries catch data is still unclear, management of cephalopod stocks is mostly rudimentary, and there is uncertainty and concern about their sustainability among fisheries managers, the fishing industry, retailers, researchers and consumers. Here, a new project is presented which aims to address and resolve ways to enhance the effectiveness of seafood sustainability in general, with the aid of a freely accessible identification and traceability tool linked to sophisticated databases, and using artificial intelligence, machine learning and blockchain technology, to provide an easy and reliable way to trace seafood using octopus as a model. The project is a contribution to UN Sustainable Development Goals 2, 9, 14, and 17

Population Connectivity and Phylogeography of a Coastal Fish, Atractoscion aequidens (Sciaenidae), across the Benguela Current Region: Evidence of an Ancient Vicariant Event

Contemporary patterns of genetic diversity and population connectivity within species can be influenced by both historical and contemporary barriers to gene flow. In the marine environment, present day oceanographic features such as currents, fronts and upwelling systems can influence dispersal of eggs/larvae and/juveniles/adults, shaping population substructuring. The Benguela Current system in the southeastern Atlantic is one of the oldest upwelling systems in the world, and provides a unique opportunity to investigate the relative influence of contemporary and historical mechanisms shaping the evolutionary history of warm-temperate fish species. Using the genetic variation in the mitochondrial DNA Control Region and eight nuclear microsatellite DNA loci, we identified the presence of two highly divergent populations in a vagile and warm-temperate fish species, Atractoscion aequidens, across the Benguela region. The geographical distributions of the two populations, on either side of the perennial upwelling cell, suggest a strong correlation between the oceanographic features of the system and the breakdown of gene flow within this species. Genetic divergence (mtDNA φ (ST) = 0.902, microsatellite F (ST) = 0.055: probability of genetic homogeneity for either marker = p<0.001), absence of migrants (less than 1% per generation) between populations and coalescent estimates of time since most recent common ancestor suggest that the establishment of the main oceanographic features of the system (2 million years ago), particularly the strengthening and position of the perennial upwelling cell, is the most likely mechanism behind the observed isolation. Concordance between mitochondrial and nuclear genetic markers indicates that isolation and divergence of the northern and southern Benguela populations of A. aequidens occurred deep in the past and has continued to the present day. These findings suggest that the Benguela Current system may constitute an ancient and impermeable barrier to gene flow for warm-temperate fish species